• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.54-61
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• 2005

An aquifer thermal energy storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop the ATES system which has certain hydrogeological characteristics, understanding the thermohydraulic process of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermohydraulic transfer for heat storage was simulated according to two sets of simple pumping and waste water reinjection scenarios of groundwater heat pump system operation in a two-layered aquifer model. In the first set of the scenarios, the movement of the thermal front and groundwater level was simulated by changing the locations of injection and pumping wells in a seasonal cycle. However, in the second set the simulation was performed in the state of fixing the locations of pumping and injection wells. After 365 days simulation period, the shape of temperature distribution was highly dependent on the injected water temperature and the distance from the injection well. A small temperature change appeared on the surface compared to other simulated temperature distributions of 30 and 50 m depths. The porosity and groundwater flow characteristics of each layer sensitively affected the heat transfer. The groundwater levels and temperature changes in injection and pumping wells were monitored and the thermal interference between the wells was analyzed to test the effectiveness of the heat pump operation method applied.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.104-104
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• 2018

이수안전도의 기준이 되는 갈수량에 대해 기후변화 시나리오에 따른 전망을 제시하였다. 충주 댐 유역을 대상으로 기준기간(1986~2000년)에서의 기상청의 관측 기상자료와 IPCC 보고서의 RCP 4.5/8.5 시나리오를 대상으로 CMIP5(Coupled Model Intercomparison Project Phase 5)에서 제공하는 기후변화 자료 중 5개의 모델(ACCESS1.3 CanESM2, CNRM-CM5, GFDL-ESM2G, HadGEM2-AO)의 기준기간과 미래기간(2011~2100년)의 기상자료를 수집하였다. 기후변화 자료는 정상성/비정상성 분위사상법과 베이지안 모델 평균기법을 통해 불확실성과 통계적 오차를 저감하였다. 미래기간에서, 강우는 RCP 4.5에서 1.74mm/year, RCP 8.5에서 3.22mm/year, 실제증발산은 RCP 4.5에서 1.09mm/year, RCP 8.5에서 1.78mm/year의 증가율을 보였다. 실제증발산을 입력자료로 활용할 수 있도록 IHACRES모델의 CMD(Catchment Moisture Deficit) 비선형 모듈의 매개변수를 변이하여 유효강우량 산정 과정을 개선하였다. 기준기간에서 관측유량자료와 IHACRES의 시뮬레이션을 통해 산정된 유량자료의 R-squared는 0.65이다. 기준기간에서의 매개변수를 고정하여 미래기간의 유량을 산정하고 유황분석을 통해 갈수량 전망하였다. 유량은 RCP 4.5에서 4.41MCM/year, RCP 8.5에서 9.66MCM/year의 증가율을 보였다. 갈수량은 RCP 4.5에서 0.30MCM/year, RCP 8.5에서 -0.47MCM/year의 증감율을 보였다. 연간 강수량 대비 실제증발산의 비율의 추세분석 결과, RCP 4.5에서는 홍수기에는 0.014%/year, 비홍수기에는 0.027%/year의 증가율을 보이며 거의 변화가 없는 추세를 확인할 수 있었다. RCP 8.5의 홍수기에는 -0.042%/year, 비홍수기에서는 0.167%/year의 증감율을 보이며 홍수기에는 실제증발산에 비해 강수량의 증가가 확연히 보였으며 비홍수기에는 강수량에 비해 실제증발산의 증가가 뚜렷이 확인되었다. RCP 8.5에서 비홍수기의 강수량 대비 실제증발산의 증가가 갈수량의 감소로 반영된 것을 확인할 수 있었다. 미래기간의 RCP 4.5/8.5에서 실제증발산의 증가로 인하여 강수량이 증가함에 따라 유입량이 증가함에도 불구하고 갈수량의 증가로 이어지지 않았다. 미래 갈수량의 감소는 하천의 건전성과 이수안전도의 위협이 될 수 있다.

• Journal of Korea Water Resources Association
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• v.55 no.1
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• pp.99-109
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• 2022

This study was intended to suggest the applicability of stepped boulder fishway using the concept of traditional boulder weir, focusing on the problems of existing concrete pool-and-weir fishways installed in mountain streams. To achieve this purpose, a stepped boulder fishway was designed and constructed as a pilot project in consideration of ascending capacity of the selected target fishes. Under the given discharge conditions, the hydraulic characteristics of the fishway were investigated in the field, and the characteristics and ascending capacity of the fishes were compared and analyzed. The fishway had a short length and steep slope, but the mean drops between each baffle were the range of 0.15 to 0.29 m, and this range satisfied the limit condition of about 0.40 m, which was in the limit of the drop that target fishes can ascend. The mean velocities of each baffle and pool were 0.82 to 0.87 m/sec and 0.13 to 0.24 m/sec. This result satisfied the conditions of burst speed (10 to 30 times of body length) and mean velocity of the resting pool (7 to 25% of burst speed) for target fishes. Since the bottom surface of the pool formed of boulders had a gentle reverse slope and rotational flow did not occur, the efficiency of fishway can be increased, and it will also be possible to solve the maintenance problem by flushing bed materials.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.41-46
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• 2022

Recently, the scale of flood damage occurring in urban areas is increasing due to climate change and urbanization, so various flooding analysis techniques are needed. In the Sadangcheon Stream basin, which has been continuously flooded since 2010, a basic plan for improving drainage was established using XP-SWMM and measures to prevent flooding were proposed. However, in the process of inundation analysis, the analysis considering the city's buildings was not conducted, resulting in a problem that the degree of flooding damage tends to be overestimated. Therefore, in this study, XP-SWMM was used to compare and analyze cases where buildings were not considered and designated as inactive areas. As a result of the study, it was analyzed if the building was not considered, the flood damaged area was 271,100 m² and the depth of submersion was 0.15 m, and if the building was considered inactive area, the flood damaged area was 172,900 m² and the depth of submersion was 0.32 m that it is under-estimated about 36% and an flow velocity around the building increased from 1.62 m/s to 1.83 m/s about 1.12 times.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.755-763
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• 2010

Fine sediment loadings from agricultural watersheds have led to habitat degradation in Lake Takkobu, northern Japan. Fifteen lake sediment core samples were obtained and analyzed to develop a chronology using physical sediment characters, $^{137}Cs$, and tephra. The reconstructed sedimentation rates over the past ca 300 years suggested that sedimentation rates increased drastically after land use development. With a natural sedimentation rate of 0.1-1.1 mm $year^{-1}$ until 1898, lake sedimentation accelerated to 0.6-12.8 mm $year^{-1}$ after 1898. The sedimentation rates after land use change, such as forestry, river engineering works, and agricultural development, were about 6-12 times higher than that under natural conditions, leading to accelerated lake shallowing over the last ca 100 years. Sedimentation rates between 1898 and 1963 differed with location in the lake because of spatial variation in the sediment flux from the contributing rivers and their watersheds. The sedimentation rate in the southern zone between 1898 and 1963 was significantly higher than that in the middle and northern zones, reflecting active sediment production associated with forestry for charcoal production and canal construction for transportation in the southern watersheds and wetlands. The sedimentation rate after 1963 did not vary among the three zones, because decreasing sedimentation was found in most of the southern sites whereas an increasing trend was observed in the middle and northern sites. This result can be explained by shallowing of lake-bottom morphology with sedimentation and the resultant reduction of sediment retention capacity in the southern zone. Moreover, the sedimentation rate at sampling sites close to river mouths increased by 5-32 times compared with natural rates before 1898. The Kushiro River, into which Lake Takkobu drains under regular flow conditions, further contributed to an increased sedimentation rate, because water from the Kushiro River flows back into Lake Takkobu during floods.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.1
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• pp.97-104
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• 2013

Methyl alcohol is one of the basic intermediates in the chemical industry and is also being used as a fuel additive and as a clean burning fuel. In this study, conversion of carbon dioxide to methyl alcohol was investigated using catalytic chemical methods. Ceramic monoliths (M) with $400cell/in^2$ were used as catalyst supports. Monolith-supported CuO-ZnO catalysts were prepared by wash-coat method. The prepared catalysts were characterized by using ICP analysis, TEM images and XRD patterns. The catalytic activity for carbon dioxide hydrogenation to methyl alcohol was investigated using a flow-type reactor under various reaction temperature, pressure and contact time. In the preparation of monolith-supported CuO-ZnO catalysts by wash-coat method, proper concentration of precursors solution was 25.7% (w/v). The mixed crystal of CuO and ZnO was well supported on monolith. And it was known that more CuO component may be supported than ZnO component. Conversion of carbon dioxide was increased with increasing reaction temperature, but methyl alcohol selectivity was decreased. Optimum reaction temperature was about $250^{\circ}C$ under 20 atm because of the reverse water gas shift reaction. Maximum yield of methyl alcohol over CuO-ZnO/M catalyst was 5.1 mol% at $250^{\circ}C$ and 20 atm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.120-127
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• 2016

This study examined the dynamic characteristics of the gate to identify the optimal gate installation direction according to the installation direction. A 1:31 scale model was constructed for a 47.5m prototype gate using acrylic. The scaled weights were tuned by adding lead weights. The first step was to measure the natural frequencies of the model gates, and compare them with finite-element analysis of the prototypes as a calibration. The scaled model was tested in a 1.6 m wide concrete flume for two orientations to determine the effects of the gate orientation on structural vibrations. Vertical vibrations were measured under a range of operational conditions, including a range of bottom opening heights and different upstream and downstream water levels. For large bottom opening heights in the normal direction, relatively large vibrations were induced by vortices shed at the plate bottom that would strike the horizontal truss member. This phenomenon was avoided in the reverse direction. For small bottom opening heights in the normal direction, these vibrations were caused by a suction force that developed at the gate bottom. The gate model in the reverse direction was preferred because of its low overall vibrational response under general gate opening and flow level combinations.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.2
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• pp.119-126
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• 1999

A numerical model using soil surface energy balance and soil heat flow equations to estimate mulched soil temperature was developed. The required inputs data include weather data, such as global solar radiation, air temperature, wind speed, atmospheric water vapor pressure, the optical properties of mulching material, and soil physical properties. The observed average soil temperature at 50 cm depth was used as the initial value of soil temperature at each depth. Soil temperature was simulated starting at 0 hour at an interval of 10 minutes. The model reliably described the variation of soil temperature with time progress and soil depth. The correlation between the estimated and measured temperature yielded coefficient values of 0.961, 0.966 for 5cm and 10cm depth of the bare soil, respectively, 0.969, 0.965 for the paper mulched soil, and 0.915, 0.938 for the black polyethylene film mulched soil. The percentages of absolute differences less than 2$^{\circ}$C between soil temperatures measured and simulated at 10 minute interval were 97.4% and 98.5% for 5 cm and 10cm for the bare soil, respectively, and 95.8% and 97.4% for the paper mulched soil, and 70.1% and 92.5% for the polyethylene film mulched soil. The results indicated that the model was able to predict the soil temperature fairly well under mulched condition. However, in the night time, the model performance was a little poor as compared with day time due to the difficulty of accurate determination of the atmospheric long wave radiation.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.857-864
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• 2011

Oxy-fuel combustion with many advantages such as high combustion efficiency, low flue gas flow rate and low NOx emission has emerged as a promising CCS technology for coal combustion facilities. In this study, the effects of the direct sulfation reaction on $SO_2$ removal efficiency were evaluated in a drop tube furnace under typical oxy-fuel combustion conditions represented by high concentrations of $CO_2$ and $SO_2$ formed by gas recirculation to control furnace combustion temperature. The effects of the operating parameters including the reaction temperature, $CO_2$ concentration, $SO_2$ concentration, Ca/S ratio and humidity on $SO_2$ removal efficiency were investigated experimentally. $SO_2$ removal efficiency increased with reaction temperature up to 1,200 due to promoted calcination of limestone reagent particles. And $SO_2$ removal efficiency increased with $SO_2$ concentrations and the humidity of the bulk gas. The increase of $SO_2$ removal efficiency with $CO_2$ concentrations showed that $SO_2$ removal by limestone was mainly done by the direct sulfation reaction under oxy-fuel combustion conditions. From the impact assessment of operation parameters, it was shown that these parameters have an effects on the desulfurization reaction by the order of the Ca/S ratio > residence time > $O_2$ concentration > reaction temperature > $SO_2$ concentration > $CO_2$ concentration > water vapor. The semi-empirical model equation for to evaluate the effect of the operating parameters on the performance of in-furnace desulfurization for oxy-fuel combustion was established.

• Journal of Korean Society of Forest Science
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• v.103 no.1
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• pp.80-86
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• 2014

$^{210}Pb$ dating was conducted to examine the influence of land use changes in the forest catchment on lake sedimentation. The Kushiro River, into which Lake Takkobu drains under regular flow conditions, contributed to an increased sedimentation rate in sampling point at the lake outflow because turbid water from the Kushiro River flows back into Lake Takkobu during floods. The elevated sediment flux from the catchment dilutes the $^{210}Pb$ concentration in sampling points at the inflow of the Takkobu River and the lake outflow, which causes fluctuations in the $^{210}Pb$ concentrations in sediment cores. The $^{210}Pb$ dating was estimated using the CRS (Constant rate of Supply) model. The dates by the CRS model in Lake Takkobu profiles were in good agreement with the dates by $^{137}Cs$. Sedimentation rates reconstructed for the past 100-150 years suggested that sedimentation rates increased drastically following land use changes. While a natural sedimentation rate of $0.01-0.03g/cm^2/year$ is observed until the 1880s, whereas lake sedimentation accelerated to $0.03-0.09g/cm^2/year$ following land use changes such as deforestation and channelization, between the 1880s and 1940s. In particular, the sedimentation rates have been associated with deforestation, channelization, agricultural development and road construction, since the 1980s, and these rates were about 9-28 times higher than those under natural conditions, leading to accelerated lake shallowing.