• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.398-405
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• 2016

The cellulose nanofibers (CNFs) were prepared by wet disk-milling (WDM) and fractionated by settling method into supernatant, middle and sediment fractions. The diameter and its distribution of the fractionated CNFs were investigated. With increasing WDM passing number, precipitation became delayed. Weight fraction at sediment fraction was decreased, whereas those at supernatant and middle fractions were increased with increasing WDM passing number. Diameter distribution of CNFs at supernatant fraction was narrowest and became broaden at middle and sediment fraction. Filtration time was longer in order of supernatant, middle and sediment fraction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.165-173
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• 1998

Analytical solutions to predict the movement rate of submerged mound are derived using the convection coefficient and the joint distribution function of wave heights and periods. Assuming that the sediment is moved onshore due to the velocity asymmetry of Stokes' second order nonlinear wave theory, the micro-scale bedload transport equation is applied to the sediment conservation. The nonlinear convection-diffusion equation can then be obtained which governs the migration of submerged mound. The movement rate decreases exponentially with increasing the water depth, but the movement rate tends to increase as the spectral width parameter, $ u$ increases. In comparison of the analytical solution with the measured data, it is found that the analytical solution overestimates the movement rate. However, the agreement between the analytical solution and the measured data is encouraging since this over-estimation may be due to the inaccuracy of input data and the limitation of sediment transport model. In particular, the movement rates with respect to the water depth predicted by the analytical solution are in very good agreement with the estimated result using the discritization technique with the hindcast wave data.

• Analytical Science and Technology
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• v.19 no.1
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• pp.45-49
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• 2006

Drilled sediment core was acquired from Jinheung catchment which was located at Jeollabuk-do Jeongeup city. Elements concentration variation were studied by neutron activation analysis using sediment core by divided 1 cm depth interval. The concentration of major element such as Na, K were increased but Fe was decrease with depth. Minimum elements concentration and particle size were observed at 17 cm depth. This depth was considered 1969 year which was great dry year recorded from the rain fall data and the sedimentation rate was calculated $0.197g{\cdot}cm^{-2}{\cdot}year^{-1}$.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.64-70
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• 1998

Forty sediment samples from Kyeonggi Bay, Korea were analyzed for butyltins, including tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) to determine their distribution and source in this area. Total butyltin concentrations in Kyeonggi Bay sediments ranged from 0.8 to 297 ng/g dry wt. with a mean value of 38 ng/g. The highest butyltin concentration was found in the innermost site in Incheon Harbor basin. The mouth of Han River had higher butyltin levels in sediments compared to open ocean. Butyltin levels correlated well with organic carbon content of sediment, but the major factor was the distance from the source area where antifouling paints were used for vessels and marine structures. Butyltin concentrations in the study area were lower than those reported for bays in other parts of the world. Considering the high toxic potential and sediment/water partition coefficient of TBT, further studies are needed to assess its biological effect in the marine ecosystem of Kyeonggi Bay.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1581-1585
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• 2006

본 연구에서는 새만금 담수호로 유입되는 유사량과 담수호의 장래퇴적분포를 추정하였다. GIS(Geographic Information System)와 범용토양유실량식(Universal Soil Loss Equation; USLE)을 적용하여 새만금 담수호 상류유역에서 발생하는 토양유실량을 산정하고, 총유실량-유사운송비(sediment delivery ratio) 법을 이용하여 담수호로 유입되는 유사량을 추정하였다. USLE에 의한 총 유실량은 2,804 천ton/yr, 새만금 소유역별 평균 유사운송비는 12%, 담수호 유입유사량은 328 천ton/yr으로 추정되었다. 새만금 담수호의 유효저수량과 유입량에 의한 포착효율(trap efficiency)을 고려하여 담수호에 실제 퇴적되는 양을 추정하고 새만금 담수호의 표고별 장래퇴적분포는 Lara method (USBR method)을 이용하였다. 새만금 담수호의 유사퇴적량은 302 천ton/yr으로 산정되었으며, Lara method에 의한 추정결과 5년, 10년 후 각각 새만금 담수호의 내용적이 0.4%, 0.7% 감소하는 것으로 나타났다.

• Journal of computational fluids engineering
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• v.18 no.2
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• pp.93-98
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• 2013

In this paper, we reported the verification of numerical simulation approach for sedimentation of the multi-size particles in a container. The comparison between experimentally measured values and numerically evaluated values on settle down process of fully mixed mixture is carried out. In an attempt to represent the natural particle size distribution, various diameters of single particles are simulated and the results are compared with the outcome of the multi-size computation. When the empirical formula for mean particle size estimation is adopted to define the sediment diameter, computation and comparison are conducted.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1299-1305
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• 2002

Thirty sediment samples of the <63${\mu}{\textrm}{m}$ fraction collected from the southwestern coast of Korea were analysed for their heavy metal (Fe, Mn, Cr, Co, Cu, Ni, Zn and Pb) concentration. The results show that sediment texture plays a controlling role on the total metal concentrations and their spatial distribution. A single lM HCl extraction procedure was used in order to assess the environmental risk of heavy metals in bottom sediments. The non-residual fraction was the most abundant pool for Mn and Pb in most samples, which means that this metals are highly avaliable in these sediments. Cr, Ni, Fe, Co, Zn and Cu were mainly associated with the residual fraction, suggesting that their concentrations are controlled significantly by transport processes with the fine particles as carriers from diffuse pollution source. Concentration enrichment ratios(CER) were calculated from the non-residual contents and their values allowed us to classify the sediments according to their environmental risk.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.126-131
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• 2007

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon "Maemi". The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon "Maemi"were predicted as $3,450\;tons/km^2/year$ and $2,920\;ton/km^2/"Maemi"$, respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.207-210
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• 2008

Recently many studys have been continued Nak-Dong river. This study recognized the importance about a rivers floor change. The Nak-Dong main river of railroad bridge(2.423Km) waegwan-eup, Cilgok-gun, Gyeongsangbuk-do analyzed to the SED2D-WES model. This study recognized the difference of the model according to the existence and nonexistence of the bridge piers. At a result of mean velocity current is higher in bridge option appeared in this case. As well sediment transportation model show that river bed change appear the part of velocity is low.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2001.11a
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• pp.92-92
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• 2001