• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.21-32
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• 2023

Interrill erosion dominates in forest areas, and the erosion rate in surface-disturbed areas is significantly increased by the development and expansion of rill. In this study, soil erosion experiments using simulated rainfall and inflow were performed to understand the development and the micromorphological changes of rill on steep slopes. The characteristic factors of the micromorphology, such as the rill cross section, rill volume, rill density, rill order, and rill sharpness, were analyzed according to steepness and location (upper or lower) of slope. The head-cut of the simultaneous incised rills by rainfall simulation moved rapidly upslope, and the randomly developed rills expanded deeply and widely with their connection. The rill cross section evolved to downslope gradually increased. The rill volume occupied about 78 % of the sediment volume, confirming that the contribution of the sediment from the rill erosion is greater than that of the interrill erosion. Although the rate of increase in rill order slowed as the slope increased, the total length and density of the rill generally increased. As the slope increased from 15° to 20°, the bed incision of rills became larger than the sidewall expansion, and the rill sharpness increased by 1.6 times. The runoff coefficient on the lower slope decreased by 12.3 % than that on the upper slope. It was evaluated that the subsoil exposures and formation changes by the rill expansion increased the infiltration rate. Although the sediment accompanying the rills generally increased with slope increase, it was directly influenced by the hydraulic velocity of enhanced rill with the local convergence and expansion in the process of the rill evolution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.3
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• pp.183-191
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• 2002

In general, the salient features of the floating breakwater have excellent regulation of sea-water keeping the marine always clean, up and down free movement with the incoming and outgoing tides, capable of being installed without considering the geological condition of sea-bed at any water depth. This study discusses the three dimensional wave transformation of the floating breakwater moored by piers, and its dynamic response numerically. Numerical method is based on the boundary integral method and eigenfunction expansion method. It is known that pier mooring system has higher absorption of wave energy than the chain mooring system. Pier mooring system permit only vertical motion (heaving motion) of floating breakwater, other motions restricted. It is assumed in the present study that a resistant force as friction between piers and floating pontoon is not applied far the vertical motion of the floating breakwater. According to the numerical results, draft and width of the floating breakwater affect on the wave transformations greatly, and incident wave of long period is well transmitted to the rear of the floating breakwater, And the vertical motion come to be large for the short wave period.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.277-288
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• 2012

Estuary is unique habitat ground under substantial changes of water quality, river side, bed material, and micro topography. Construction of SinGok underwater weir with excessive dredging for downstream of weir has changed hydraulic conditions of Han River. This study investigates spatial changes of estuary and expansion process of vegetation on sandbar for JangHang estuary in Han River through analysis of physical and ecological characteristics. As a result of investigation, we found that area of sandbar in JangHang estuary is expanded six times compared between 1985 and 2006, and area of Phragmites australis is gradually decreased while area of Salix subfragilis Anderson. is increased. Also the analysis result of soil layer shows that the Jang-Hang wetlands are created by effect from river, and woody plants are settled from middle part of wetlands, then spread to upper and lower part of wetlands.

• Journal of The Korea Institute of Healthcare Architecture
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• v.28 no.4
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• pp.61-69
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• 2022

Purpose: In response to the rapid spread of COVID-19 in 2020, the government supported facilities and equipment through the 'Urgent Isolation Ward Expansion Project'. Design and remodeling of efficient negative pressure isolation facilities had to be done in a short period of time, and the performance gap between facilities was very large because the types of hospitals and wards of existing medical facilities were diverse. In order to secure the stability of isolation wards between medical facilities and reduce the facility gap, guidelines for planning isolation wards considering the diversity of each hospital should be appropriately presented. In consideration of these points, this study aims to provide basic data for future remodeling guidelines for each plan type of the negative pressure isolation ward first. Methods: We analyzed the plans before and after the change of 13 case hospitals that performed the urgent care bed expansion project for COVID-19 confirmed patients. Before the remodeling, the current status of the facility was analyzed according to the type of corridor, the location of the nursing station, and the location of the elevator. After remodeling, the flow of medical staff and patients, the flow of entry and exit of clean and contaminated items, and the space of negative pressure and non-negative pressure areas. Results: The ward type was divided into three types according to the corridor type and room arrangement: double loaded corridor type with two side wards, race track type with one side ward, and race track type with two side wards. Based on these three types, the standard floor plan type of the isolation ward was proposed in terms of the location of the elevator bank and Nurse station. Implications: When the existing general ward is converted into a negative pressure isolation ward, this study can be a basic data to present customized guidelines for each ward type.

• Journal of Korean Society of Forest Science
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• v.79 no.3
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• pp.269-277
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• 1990

In planning the disaster prevention by the erosion control facilities, it is essential to focus on the microtopography of the channel bed and the chronological process of sedimental movement in the torrential streams. For this purpose, the microtopographical change of the channel bed and the effects of the erosion control facilities in the mountain torrents were analyzed by the experimental channel and the field survey of the torrents where low-dam series had been constructed in the channel. The results of this experiment showed that the effects of construction of the low-dam series on the channel bed fixiation were the prevention of the local scouring in the experimental channel and the expansion of flow channel width and deposit space. The results are summarized as follows : 1. When the low-dam series were constructed over the whole channel bed (L'/L=1), the conning water and the sediment were seperated, simultaneously resulting in deposition of sediment and reduction of the tractive force for the running water. Therefore, the F.A. (Fluctuation area in cross-section: value was decreased to about 65% compared with that of non-work (L'/L=0). 2. The efficiencies of the low-dam series on the channel width were increased with an increment in length of working space. After the construction of low-dam series on the whole channel bed (L'/L=1), flow channel width was increased to about 1.53 times compared with that of non-work (L'/L=0). 3. It needs a deposition area to store the sediment with decrease in tractive force. The low-dam series in the experimental channel widened the deposition area about 2.10 times compared with that of non-work.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.150-163
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• 2015

Gasification technology is one of the representative next-generation fossil fuel utilization technologies, converting low grade fossil fuels such as coal, heavy residue oil, pet-coke into highly clean and efficient energy sources. Accordingly, related market demand for gasification technology is ever increasing steadily and rapidly. A few years ago, conventional pulverized coal utilization technology had an edge over the gasification technology but the most significant technical barrier of limited capacity and availability has been largely overcome nowadays. Futhermore, it will be more competitive in the future with the advancement of related technologies such as gas turbine, ion transfer membrane and so on. China has recently completed a commercialization-capable large-scale coal gasification technology for its domestic market expansion and foreign export, rapidly becoming a newcomer in the field and competing with existing US and EU technical leadership at comparable terms. Techno-economic aspect deserves intensive attention and steady R&D efforts need to continue in organized, considering that gasification technology is quite attractive combined with $CO_2$ capture process and coal to SNG plant is economically viable in Korea where natural gas is very expensive. In the present paper, recent technology development and commercialization trend of many leading companies with coal gasification expertise have been reviewed with significant portion of literature cited from the recently held '2014 Gasification Technology Conference'.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.25-31
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• 2018

In this study, the Controlled Low Strength Material (CLSM) was investigated to utilize the bottom ash and fly ash generated in the Circulating Fluidized Bed Combustor (CFBC). It was confirmed that the CFBC fly ash (CFBC-F) and CFBC bottom ash (CFBC-B) had an irregular particle shape through SEM measurement. According to the results of the hazard analysis, it was also confirmed that they were environmentally safe. In the case of mixing with CFBC-F, the unit quantity was increased. Regarding the rate of change of length, shrinkage in the range of -0.05~0.50% occurred in the air dry curing condition and expansion in the range of 0.1~0.6% in the sealed curing condition. Compressive strength was increased in the sealed curing condition compared to the air dry curing condition because there was enough moisture for hydration reaction in the long term. Therefore, the results of this study are likely be used as basic research data of mine filler materials.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.565-571
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• 2005

The method to decide media sphericity on the filter has been investigated. The sphericity, the ratio of the surface area of an equal volume sphere to the real surface area of the particles, is one of major physical characters of media affecting the bed expansion during backwash. The media in each treatment plant may have different sphericity, and the sphericity of the media in the filter may be changed as backwashing has been conducted regularly for a long time. Media from twelve water treatment plants under KOWACO have been collected and selected to insure various and practical sphericities. The sphericity of each media has been calculated by using well known equations. For example, Kozeny equation, Dahmarajah equation and so on. The experiment results have indicated that the sphericity of each water treatment plant is different. Although the sphericity values measured by different methods were turned out to be diverse values, the order in the magnitude seemed to be the same. The sphericity values of sand media were in the range of 0.71-0.82 and those of anthracite were placed between 0.49 and 0.56 by the Dharmarajah equation.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.3
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• pp.71-87
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• 2007

In order to improve and manage rationally for Youngdam creek in Haman-gun, the channel change, water quality and ecological adaptation etc. were evaluated by monitoring during three years. The distinct differences of channel characteristics appeared in the extents of bed excavation and the revetment methods because overall reconstruction was occurred intense disturbance of width expansion and levee construction etc. The scour and deposition were caused according to channel characteristics of ripple and pool, and the adaptation of vegetation was distinguished from each revetment methods clearly. Water quality was maintained first class on the basis of BOD as 0.5~1.5mg/${\ell}$. The vegetation appeared in 380 species close-to-nature river improvement before, but 64 species it after one year, 159 species it after two year and 158 species it after three year. The animal life appeared in 123 species of close-to-nature river improvement before, but 103 species it after one year, 116 species it after two year and 119 species it after three year.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.127-133
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• 2018

The Saemangeum master plan includes dredging and waterproofing materials, construction projects that can change the hydraulic characteristics of the Saemangeum and Mangyeong and Dongjin River basins. In this study, the river safety of 2030 when the Saemangeum master plan was completed for 100 year frequency, 500 year frequency and 100 year frequency applied RCP 8.5 scenario was examined using Delft3D. As a result of the analysis, it was confirmed that there was no overflowing point at the 100 year frequency, but the difference between the flood level and the river bank elevation was relatively small at the curved and river joint part. At the 100-year frequency with the 500-year frequency and the RCP 8.5 scenario, the possibility of overflowing at several locations was confirmed. The possibility of river bed loss due to fast velocity appears in the upstream part of Mankyung River and it is necessary to monitor the safety of hydraulic structures continuously. In addition, it is expected that the expansion of the area showing the characteristics of the lake due to dredging will affect the sediment mechanism and water quality, so detailed and diverse studies will be needed.