• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.819-829
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• 2018

The bed change survey was carried out and its tendency was analyzed at the downstream of the Singok Submerged Weir in the Han River Estuary (HRE). In order to focus on the bed change in the low flow channel, we calculated the mean bed elevation based on the bankfull discharge. Thanks to the amount of bed changes calculated by using the 'averaged bed', we could compare the riverbeds of various periods with consistent criteria. In the HRE, revealed was the bed change cycle between degradation by flood and aggradation by tide at the non-flood season.

• Radiation Oncology Journal
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• v.31 no.4
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• pp.228-233
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• 2013

Purpose: The aim of this study was to evaluate changes in breast tumor bed volume during whole breast irradiation (WBI). Materials and Methods: From September 2011 to November 2012, thirty patients who underwent breast-conserving surgery (BCS) followed by WBI using computed tomography (CT) simulation were enrolled. Simulation CT scans were performed before WBI (CT1) and five weeks after the breast irradiation (CT2). The tumor bed was contoured based on surgical clips, seroma, and postoperative change. We retrospectively analyzed the factors associated with tumor bed volumetric change. Results: The median tumor bed volume on CT1 and CT2 was 29.72 and 28.6 mL, respectively. The tumor bed volume increased in 9 of 30 patients (30%) and decreased in 21 of 30 patients (70%). The median percent change in tumor bed volume between initial and boost CT was -5%. Seroma status (p = 0.010) was a significant factor in tumor bed volume reduction of 5% or greater. However, patient age, body mass index, palpability, T stage, axillary lymph node dissection, and tumor location were not significant factors for tumor bed volumetric change. Conclusion: In this study, volumetric change of tumor bed cavity was frequent. Patients with seroma after BCS had a significant volume reduction of 5% or greater in tumor bed during breast irradiation. Thus, resimulation using CT is indicated for exquisite boost treatment in breast cancer patients with seroma after surgery.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2321-2326
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• 2018

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to $600^{\circ}C$ and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of $550^{\circ}C$, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.291-300
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• 2012

We conducted a three-dimensional numerical simulation by using the FLOW-3D, with RANS as the governing equation, in an effort to track the dam-break wave.immediately after a dam break.in areas surrounding where the dam break took place as well as the bed change caused by the dam-break wave. In particular, we computed the bed change in the movable bed and compared the variation in flood wave induced by the bed change with our analysis results in the fixed bed. The analysis results can be summarized as follows: First, the analysis results on the flood wave in the L-shaped channel and on the flood wave and bed change in the movable-bed channel successfully reproduce the findings of the hydraulic experiment. Second, the concentration of suspended sediment is the highest in the front of the flood wave, and the greatest bed change is observed in the direct downstream of the dam where the water flow changes tremendously. Generated in the upstream of the channel, suspended sediment results in erosion and sedimentation alternately in the downstream region. With the arrival of the flood wave, erosion initially prove predominant in the inner side of the L-shaped bend, but over time, it tends to move gradually toward the outer side of the bend. Third, the flood wave in the L-shaped channel with a movable bed propagates at a slower pace than that in the fixed bed due to the erosion and sedimentation of the bed, leading to a remarkable increase in flood water level.

• The Journal of the Korea Contents Association
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• v.11 no.6
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• pp.486-494
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• 2011

River bed change due to various factors in watershed and/or river environment would one of the most important issues in river management. To judge whether the river bed was aggrading or degrading, normally we use the change in thalweg or average bed, calculated using the design flood of the river. The present study is to figure out the problems of the existing methods and to propose a new concept of average river bed using annual maximum flood. To evaluate the new method, it was applied to the Nakdong River. We use the river bed data surveyed in 1983, 1993, and 2005. The results showed that there were no significant river bed change during 1983 and 1993, while the river bed was degraded significantly during 1993 and 2005. In the latter period, the river had severe degradations, 2~3 m in average sense and 5 m for the maximum in the middle reach(120~200 km from river mouth), and 1~2 m in average in the upper reach(200~240 km from river mouth). For the upstream reach of the confluence of the Naesung River(about 240 km from river mouth), most of the river bed change seemed to be only local phenomena. The main cause of the river bed change in the Nakdong River seems to be massive gravel mining in the middle reach of the river.

• Journal of Environmental Science International
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• v.19 no.10
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• pp.1219-1227
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• 2010

In this study, the sensitivity analysis of bed changes due to the various sediment transport equations have been conducted for 80 km reach of the Lower Nakdong River using the HEC-6 which is one dimensional numerical model. The bed elevation changes according to the different sediment transport formulas were compared and analyzed quantitatively. As a result of the numerical simulation, the final bed elevation calculated by Engelund and Hansen(1967), Ackers and White(1973), and Yang(1979) formulas was similar to one another in configuration. The bed change simulated by Engelund and Hansen(1967) were greatest among them, for example, 5.5 m deposition and 2.9 m erosion for 100 years. Also, in the case of Toffaleti (1969) equation, the maximum bed deposition of 8.04 m after 100 years was induced at the 73 km location upstream of the Nakdong River Estuary Barrage. Meyer-Peter-M$\ddot{u}$ller(1948) and Wilcock(2001) formulas produced the deposition only at the upstream end and there was little bed change in the downstream area. The unreal bed configuration of continuously up and down pattern was simulated by Laursen(1958) transport equation.

• The Korean Journal of Quaternary Research
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• v.20 no.2
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• pp.1-10
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• 2006

Flooding hazard caused by natural and artificial environmental changes is closely associated with change in river bed configuration. This study is aimed at explaining a river-bed change related to soil erosion in the Keum river basin using GIS and RS. The USLE was used to compute soil erosion rate on the basis of GIS. River-bed profiles stretching from Kongju to Ippo were measured to construct a 3D-geomorphological map. The river-bed change was also detected by remote sensing images using Landsat TM during the period of 1982 to 2000 for the Keum river. The result shows that USLE indicates a mean soil erosion rate of $1.8\;kg/m^2/year$, and a net increase of a river-bed change at a rate of $+5\;cm/m^2$/year in the Kangkyeong area. The change in river-bed is interpreted to have been caused by soil erosion in the downstream of the Keum river basin. In addition river-bed change mainly occurred on the downstream of the confluence where tributaries and the main channel meet. Other possible river-bed change is caused by a removal of fluvial sand aggregates, which might have resulted in a net decrease of exposed area of sediment distribution between 1991 and 1995, while a construction of underwater structures, including a bridge, a reclamation of sand bars for rice fields and dikes, resulted in an increase of the exposed area of river-bed due to sediment accumulation.

• 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 Wetlands Research
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• v.9 no.3
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• pp.51-61
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• 2007

In natural river, river-bed change is greatly influenced by the various factors such as river improvement, change of watershed land use, construction of dam and reservoir, gravel mining, and so on. The knowledge about river-bed change in the river is essential in the river modification, wetlands plan, and maintaining stable alluvial rivers. In this study, river-bed change in the future was predicted by investigating river channel characteristics which play dominant role in the formation of channel and based on the numerical model through river survey and the grain size analysis. The Proposed investigation and model was applied to the Geum river and the Miho stream which have been experienced river degradation due to river aggregate dredging and now seams to be stable. The result of potential river-bed change which was estimated by investigating channel characteristic including slope of channel, friction velocity, and so on is similar to that which was estimated based on the numerical model. It was found that the Geum river and the Miho stream will be stable. In the future, if considering the characteristics of river channel which is estimated by the river-bed scour, sediment, and so on, it is possible that river improvement and wetland restoration plan are established stably and naturally.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.23-31
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• 2002

Processes in an iron ore sintering bed can characterized as a relatively uniform progress of fuel, cokes combustion and complicated physical change of solid particles. The sintering bed was modelled as an unsteady one-dimensional progress of the fuel layer, containing two phases: solid and gas. Coke added to the raw mix, of which the amount is about 3.5% of the total weight, was assumed to form a single particle with other components. Numerical simulations of the condition in the iron ore sintering bed were performed for various parameters: moisture contents, cokes contents and air suction rates, along with the various particle diameters of the solid for sensitivity analysis. Calculation results showed that the influence of these parameters on the bed condition should be carefully evaluated, in order to achieve self-sustaining combustion without high temperature section. The model should be extended to consider the bed structural change and multiple solid phase, which could treat the inerts and fuel particles separately.