• Korean Journal of Microbiology
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• v.43 no.4
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• pp.256-263
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• 2007

We performed the biochemical characteristics, molecular epidemiologocal analysis, and drug susceptibility test on V. vulnificus isolated from environmental sources in Incheon. For this study, 233 strains were isolated from seawater, sediment, shellfish. V. vulnificus isolates were divided into 15 biochemical groups, which were positive for ONPG and Amygdalin test. Among the 209 strains, 206 (98.6%) strains and 110 (52.6%) strains revealed positive for vvhA and viuB gene, and the viuB gene detection rates of V. vulnificus from seawater, shellfish and sediment were 48%, 48.5% and 61.6%, respectively. From disc diffusion test on 175 isolates, most of strains were sensitive to Imipenem (100.0%), Sulfamethoxazole/trimethoprim (98.9%), Tetracycline, Ciprofloxacin (98.3%), Ampicillin/sulbactam (97.1%), Ohloramphenicol (96.6%), Cefepime (94.9%) and Ceftriaxone (94.8%), multi-drug resistance rates was 31.5% of seawater, 34.4% of sediment and 29.2% of shellfish. PFGE was performed on 233 V. vulnificus isolates with the objective of investigating the extent of genetic diversity of these isolates in our region. We could find that at least 126 different PFGE patterns were generated according by 90% of similarity and 13 clusters by 58% of similarity. The major cluster was type I (44.6%) during the most of the year, and type J was frequent pattern in June and October. There were 9 distinct PFGE types in July, 8 types in August, 7 types in June, 6 types in September, 5 types in October 3 types in May and 1 type in March.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.821-834
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• 2015

This study presents the analysis of flow and bed change characteristics considering bed protection work built on the immediate downstream of weir to protect river bed from scouring. The study area is 37km reach from Hyunpoong station to Masuwon station including Hapcheon- Changryoung multi-function weir in the Nakdong river. CCHE2D model is calibrated and validated for evaluating the flow and bed change characteristics during Typhoon Kompasu in 2010. Three simulation conditions are set up: Case 1 is a natural channel without installation of weir. Case 2 involves an installation of weir in the natural channel. Case 3 involves an installation of weir with bed protection in the natural channel. Flood frequency (50, 100 and 200yr) is applied to each scenario to analyze the effects of bed protection work. While the sediment rate is increased in the downstream of fixed gate and sluice-type gate, river bed scouring rate is increased in the downstream of lift-type gate in Case 2 comparing with the results of Case 1. The river bed scouring is not occurred in the immediate downstream of weir (~30m) due to the effect of bed protection, but larger amount of sediment is occurred in the downstream of weir (60m~) which the bed protection is not installed comparing with the results Case 1. Through the results of simulation considering bed protection work, this study would be helpful to expect bed change and operate the weir as well as manage.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.2
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• pp.1-11
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• 2018

As a result of climate change, mountain sediment disasters due to localized heavy rain and mountain development are occuring more frequently, thus, increasing social attention to and demand for soil erosion control projects. However, since 2011 Seoul Wumyeon Mountain landslide, the public is expressing increasing anxiety as well as negative perception regarding defective project results. Therefore, this study investigated promotional terms and information media related to soil erosion control projects according to the consumer in order to increase awareness of soil erosion control projects. In this study, the information consumers were divided into experts and the general public and conducted a survey related to promotional terms and media for communicating relevant information. In the result, the experts chose landslide prevention and recovery projects (41.8%) as an appropriate promotional term for soil erosion control projects. The general public, however, chose mountain sediment disaster prevention projects (32.5%) as the appropriate promotional term. However, the analysis showed that it would be necessary to develop an promotional term that can encompass the concept of 'disaster prevention' including forest and soil disaster as the word 'landslide' can suggest soil erosion control is limited to landslides only. In the survey regarding the media for communicating information related to soil erosion control projects according to the consumer type, the experts preferred radio and TV as media to communicate the relevant information, while, among the general public, the youths preferred social media such as Facebook and Twitter (22.22%) and adults radio and TV (34.07%), As for the most effective way to promote soil erosion control projects, the experts chose traditional promotinal media such as newspaper, radio, and TV (0.172) whereas the adults and youths preferred the internet and Facebook (0.089). It appears that using the preferred media for communicating information related to soil erosion control projects according to the consumer type will be effective way to promote soil erosion control projects.

• 한국해양학회지
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• v.19 no.2
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• pp.153-162
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• 1984

This study was conducted to interpret the relations between the polychaete community and its environments in Kwangyang Bay during July, 1982. The type of sediments in the study area varies from sand to clay and the organic content obtained by ignition was in the ranges of 0.3% to 15.4%. The polychaetes which occurred at 25 stations comprised 70 species representing 63 genera and had an average density of 490 animals/m$\^$2/. The most abundant species were Lagis bocki (20%), Lumbrineris longifolia (10%), Chohe teres (7%), and Sternaspis scutata (5%). The polychaete populations show the highest density in muddy sand sediments and have a tendency to decrease their abundance in finer sediments such as bud and clay. The individual numbers of each feeding type show the same tendency. Kwangyang Bay consists of three distinct characteristic communities, representing different physical and biological factors: delta community, muddy flat community and channel community. Delta community has very poor organisms and seems to be determined by physical factors such as tidal current, and by sediment conditions and seems to be determined by physical factors such as tidal current, and by sediment conditions and by the food availability. Muddy flat community shows more diverse and higher abundance than delta community but seems to be impoverished by the stress of oxygen deficiency in sediments. Channel community has the highest density in the study area and comprises more various feeding types. This is probably due to the supply of allochthonous materials from the Seomjin River and offshore as food, the heterogeneous sediments and some biological interactions within habitats.

• Journal of Korean Society of Forest Science
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• v.97 no.3
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• pp.326-331
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• 2008

This study was carried out to analyze the characteristics of each factors by using the quantification theory(I) for prediction of landslide hazard area. The results obtained from this study were summarized as follows; The stepwise regression analysis between landslide sediment ($m^3$ ) and environmental factors, factors affecting landslide sediment ($m^3$ ) were high in order of mixed (forest type), < 15 cm(soil depth), 801~1,200 m (altitude), $31{\sim}40^{\circ}$ (slope gradient), 46 cm < (soil depth), 1,201 m < (altitude) and s(aspect). According to the range, it was shown in order of soil depth (0.3784), altitude (0.2876), forest type (0.2409), slope gradient (0.1728) and aspect (0.1681). The prediction of landslide hazard area was estimated by score table of each category. The extent of prediction score was 0 to 1.2478, and middle score was 0.6239. Class I was over 1.1720, class II was 0.7543 to 0.1719, class III was 0.4989 to 0.7542 and class IV was below 0.4988.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.265-275
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• 2012

As climate change is becoming a growing concern and the importance of water management is increasing, the retention of carbon and nutrients in wetland soils including inland and coastal area has become important. In this study, retention characteristics of organic matter and nutrients of coastal sediment and soils in different types of wetlands such as constructed wetland, natural (inland marsh, estuary, tidal flat) wetlands were investigated. A correlation analysis was also performed to understand the relationship among organic matter properties, nutrient concentrations and soil texture of wetland soils. The degree of retention of organic matter and nitrogen in wetland soils varied with the wetland type. Inland wetlands retain more nitrogen than estuary or coastal wetlands, and natural wetlands retain more organic matter and nitrogen than constructed ones. Coastal sediments in a bay area where seawater circulation is restricted have more nutrients than those in estuary or tidal flats where seawater circulates well. The results showed that the sediment chemical oxygen demand has a high correlation with the total organic carbon and the total nitrogen in the studied area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.95-109
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• 2008

We numerically analyzed the nonlinear shoaling, a plunging breaker and its accompanying energetic suspension of sediment at a bed, and a redistribution of suspended sediments by a down rush of preceding waves and the following plunger using SPH with a Gaussian kernel function, Lagrangian Dynamic Smagorinsky model (LDS), Van Rijn's pick up function. In that process, we came to the conclusion that the conventional model for the tractive force at a bottom like a quadratic law can not accurately describe the rapidly accelerating flow over a swash zone, and propose new methodology to accurately estimate the bottom tractive force. Using newly proposed wave model in this study, we can successfully duplicate severely deformed water surface profile, free falling water particles, a queuing splash after the landing of water particles on the free surface and a wave finger due to the structured vortex on a rear side of wave crest (Narayanaswamy and Dalrymple, 2002), a circulation of suspended sediments over a swash zone, net transfer of sediments clouds suspended over a swash zone toward the offshore, which so far have been regarded very difficult features to mimic in the computational fluid mechanics.

• Economic and Environmental Geology
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• v.39 no.1 s.176
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• pp.39-51
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• 2006

Rare earth elements(REEs) in transgressive shelf core sediments were analysed to identify constraints of REE distribution patterns and sediment provenances in the northern East China Sea(ECS). Sediments of Chinese and Korean rivers, such as Huanghe and Yangtz rivers, Keum and Yeongsan rivers that supply sediments to the northern ECS, were also analysed to figure out their typical REE distribution patterns. The distribution patterns of Chinese and Korean river sediments, which are normalized with upper continental crust (UCC) REE values, appear to be enriched in middle rare earth elements (MREEs) in Chinese river sediments, whereas in light rare earth elements (LREEs) in Korean river sediments. We assign the MREE-enriched convex-type distribution pattern in Chinese river sediments as 'C-type', and the LREE-enriched linearly decreasing pattern in Korean river sediments as 'D-type'. A major constraint of the REE concentration in northern ECS core sediments is interpreted to be LREE-enriched monazite $((Ce,\;La)PO_4)$ that is ubiquitous in and around the study area. Meanwhile, the distribution pattern of northern ECS sediments appears to be between the C-type and the D-type. We suggest that the nothern ECS sediments are the mixture of China and Korea riverine sediments that have been accumulated in paleo-river mouth, paleo-coast, and present-day shelf environment as well.

• Journal of Ocean Engineering and Technology
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• v.25 no.5
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• pp.15-20
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• 2011

This study carried out a series of experiments involving impact tests (Drop Weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditiAn experimental study was carried out to study the solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. The lift forces acting on a fluidized particle play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport, the cleaning of particles from surfaces, etc. In this study a clear acrylic pipe was used to observe the movement of solid particles. Annular velocities varied from 0.4 to 1.2 m/s. The effect of the annulus inclination and drill pipe rotation on the carrying capacity of a drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully-developed flows of water and aqueous solutions of CMC (sodium carboxymethyl cellulose) and bentonite. The rotation of the inner cylinder was efficient at carrying particles to some degree. For a higher particle volume concentration, the hydraulic pressure loss of the mixture flow increased because of the friction between the wall and solids or between solids.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.368-368
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• 2016

점착성 유사는 응집현상을 통해 크기와 밀도를 바꾸고 이에 따라 부유 및 이동에 큰 영향을 미치는 침강속도가 지속적으로 변화한다. 따라서 점착성 유사의 거동을 이해하기 위해서는 응집현상에 대한 고려가 필수적으로 이루어져야 한다. 현재까지 이루어진 응집현상 모형은 크게 Population balance equation type 모형(PBE)과 Floc growth type 모형(FGM)으로 나뉜다. PBE 모형은 점착성 유사의 입도분포를 모의할 수 있는 장점이 있는 반면에 닫힌 계에서 질량보존을 만족시키지 못하는 단점을 가진다. FGM 모형은 간단한 식을 통해 질량보존을 만족시키고 수치적으로 효율적인 모의를 할 수 있는 반면 입도분포를 모의할 수 없는 단점을 가진다. 이러한 장단점으로 인해 PBE 모형은 유사이동모형과 결합되어 이용된 사례가 없으며 FGM 모형은 유사이동모형과 결합되어 평균적인 점착성 유사의 거동만을 모의하는 연구에 이용되었다. 본 연구에서는 Stochastic floc growth type 모형(SFGM)의 개발에 따라 이해할 수 있는 점착성 유사이동의 특성과 이를 유사이동 모형과 결합시키는 방향에 대해 검토한다. 현재까지 진행된 연구 결과를 분석하면 SFGM은 질량보존을 만족시키면서도 점착성 유사의 입도분포를 모의할 수 있는 장점을 가지는 것으로 판단된다. 특히 난수발생의 단계에서 적절한 확률분포형을 선정하고 확률매개변수의 보정이 이루어지는 경우에는 높은 정확도를 가지는 입도분포 모의가 가능하다. 가는 모래를 대상으로 하는 비점착성 유사의 경우에는 추계학적인 유사이동 모형의 개발이 활발히 이루어져 왔다. 개발된 모형은 실제 측정값에 적용되어 다양한 학술적 가능성을 보여왔다. 따라서 SFGM의 개발이 점착성 유사의 이동모형과 결합되는 경우에는 점착성 유사가 지배적인 다양한 환경에서의 거동 특성을 이해할 때 매우 유용할 것으로 판단된다. 응집모형은 난류의 강도에 지배적인 영향을 받으며 유사의 입경 및 밀도 변화를 계산한다는 점을 고려할 때 유사이동 모형 역시 난류 강도에 대한 정보를 계산할 수 있는 지배방정식을 필요로 한다. 향후 개발될 추계학적 점착성 유사의 이동모형은 난류에 대한 정보, SFGM의 결합 등을 필요조건으로 가진다.