• Economic and Environmental Geology
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• v.46 no.3
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• pp.267-278
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• 2013

The East African Rift System(EARS) is known to be hosted epithermal Au-Ag deposits, and the best-known example is Main Ethiopian Rift Valley(MER) related to Quaternary bimodal volcanism. Large horst-graben system during rifting provides open space for emplacement of bimodal magmas and flow channel of geothermal fluids. In recent, large hydrothermally altered zones(Shala, Langano, and Allalobeda) and hot spring related to deeply circulating geothermal water have been increasing their importance due to new discoveries in MER and Danakil depression. The hot springs in Shala and Allalobeda occur as boiling pool and geyser on the surface, whereas some areas didn't observe them due to decreasing ground water table. The host rocks are altered to quartz, kaolinite, illite, smectite, and chlorite due to interaction with rising geothermal water. The hot springs in MER are neutral to slightly alkaline pH(7.88~8.83) and mostly classified into $HCO_3{^-}$ type geothermal water. They are strongly depleted in Au, and Ag, but show a higher Se concentration of up to 26.7 ppm. In contrast, siliceous altered rocks around hot springs are strongly enriched in Pb(up to 33 ppm, Shala), Zn(up to 313 ppm, Shala), Cu(up to 53.1 ppm, Demaegona), and Mn(up to 0.18 wt%t, Shala). In conclusion, anomalous Se in hot spring water, Pb, Zn, Cu, and Mn in siliceous altered rocks, and new discoveries in MER have been increasing potential for epithermal gold mineralization.

• Land and Housing Review
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• v.3 no.1
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• pp.33-43
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• 2012

The research which it sees is the simulation research for "The Ecological Diversion of Forest Land-Use System". It accomplished the simulation which applies a permission standard, it developed escape it did a model and the basic draft. From the research which it sees in order to investigate the application characteristic of natural intimate mountain district application standard the mountain district whole aspect instance middle actual object a time mountain district use standard about under selecting which it will yell it applied. "Natural intimate mountain district development standard triangular position plan research" from compatibility of the mode of life mountain district whole aspect permission standard which is proposed about under investigating it presented the improvement program and a institutional improvement direction of corresponding standard. About under preserving plan it applies the yearly environment the mountain district to sleep it prepares the foundation for it accomplished the transcendental research for. With the achievement resources which the mountain district has resultantly must preserve a value, limit of the development size it will be able to minimize the effect which it follows in development, the arrangement method back could be proposed, also the case which will use the mountain district where it is damaged induces the development which cabinets to the concept of demobilization, the case which will apply the existing forest resources takes a triangular position with the act it will be able to increase the circulating value of the resources and will do.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.457-464
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• 2022

In this study, XRF, Loss on ignition, SEM, and PSA analysis were performed on four types of fly ash in Vietnam and compared with fly ash in Korea. As a result, PC boiler fly ash in Vietnam has a similar chemical composition to that of PC boiler fly ash in Korea, where the content of SiO₂, Al₂O₃, and Fe₂O₃ accounts for about 70%. In addition, the result showed that blast furnace slags in Vietnam and Korea have similar quality criteria and performance. A binder material mixing test using four types of fly ash supplied from Vietnam was conducted, and the compressive strength ranged from 7.60 to 13.25 MPa after 28 days of curing. Vinh Tan fly ash showing the highest compressive strength was selected as the soil injection material for the chemical grouting method. For the formulation of the chemical grouting method, sodium silicate No.3 and silica-sol were used as liquid-A. As a result of measuring the gel time and the compressive strength of the homogel, they showed good performance satisfying the quality criteria applied in Korean construction fields. Therefore, Vinh Tan fly ash can be used as a soil injection material for the chemical grouting method.

• Journal of Environmental Science International
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• v.26 no.11
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• pp.1267-1274
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• 2017

A Controlled Low-Strength Materials (CLSM) is suitable for mine backfilling because it does not require compaction owing to it high fluidity and can be installed quickly. Therefore, a CLSM utilizing $CO_2$-solidified Circulating Fluidzed Bed Combustion (CFBC) coal ash was developed and it's properties were investigated, since. $CO_2$-solidification of CFBC coal ash can inhibit exudation of heavy metals. The chemical composition and specific surface area of Pulverized coal Combustion fly ash and CFBC fly ash were analyzed. The water ratio, compressive strength and length change ratio of CLSM were confirmed. The water ratios differed with the specific surface area of the CLSM. It was confirmed that the porosity of CLSM affected its compressive strength and length change ratio.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.37-41
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• 2012

Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.116-129
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• 1990

A rational management of water resources in estuary reservoirs necessiates the prediction of water quality. In this study, a multiple box model for the water quality prediction was developed as a tool for the purpose of examining an adequate way to improve and maintain the water quality. Some submodels that are suitable for simulating the mixing behavior of pollutant materials in a lake were considered in this model. The model was appiled for predicting water qualities of Haenam Esturay Reservoir. The result from this study can be summarized as follows : 1.A water quality simulation model that can predict the 10-day mean value of water qualities was developed by adding some submodels that simulate the concentrations of chlorophyll-a, BOD, T-P and T-N to the existing Multiple Box Model representing the mixing and circulating of materials by the hydarulic action. 2.As input data for the model developed, the climatic data including precipitation, solar radiation, temperature, cloudness, wind speed and relative humidity, and the water buget records including the pumping discharge and the releasing discharge by drainage gate were ollected. The hydrologic data for the inflow discharge from the watershed was obtained by simulation with the aid of USDAUL-74/SNUA watershed model. Also the water quality data were measured at streams and the reservoir. 3.As a result of calibration and verification test by using four comonents of water quality such as Chlorophyll-a, BOD, T-P and T-N, it was found that the correlation coefficeints between the observed and the simulated water qualities showed greater than 0.6, therefore the capability of the model to simulate the water quality was proved. 4.The result based on the model application showed that the water quality of the Haenam Estuary Reservoir varies seasonally with the harmonic trend, however the water quality is good in winter and get worse in summer. Also it may be concluded that the current grarde of water quality in the Heanam Esutary Reservoir is ranked as grade 4 suitable only for the agricultutal use.

• Water for future
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• v.21 no.1
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• pp.67-76
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• 1988

Analyzed was the circulation phenomena in the open channel with sudden expansion, by applying the Galerkin's finite element method to the depth-averaged 2-dimensional continuity and momentum equations. Wave tests were done in the simplified channel in order to review the validity of this newly developed model and the computed results were within 0.5% of $L_2$-norm error, and application of this model to the simulation of simplified dam-break gave very close results compared with the analytical solution, thus, it can be concluded that this model is valid and efficient. The main flow in the expanded channel was defined as a new initial condition with given velocity and the flow in the expanded portion was at rest in simulating the circulation, and besides the Neumann's condition the slip boundary condition for lateral wall was found to be proper condition than the no-slip condition. It can be concluded, from the numerical tests in the sudden expension, that the circulating phenomena depend mainly on the convective inertia and the effect of turbulence due to bottom shear and lateral shear is insignificant.

• Journal of Power Electronics
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• v.15 no.2
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• pp.455-468
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• 2015

A microgrid (MG) with integrated renewable energy resources can benefit both utility companies and customers. As a result, they are attracting a great deal of attention. The control of a MG is very important for the stable operation of a MG. The droop-control method is popular since it avoids circulating currents among the converters without using any critical communication between them. Traditional droop control methods have the drawback of an inherent trade-off between power sharing and voltage and frequency regulation. An adaptive droop control method is proposed, which can operate in both the island mode and the grid-connected mode. It can also ensure smooth switching between these two modes. Furthermore, the voltage and frequency of a MG can be restored by using the proposed droop controller. Meanwhile, the active power can be dispatched appropriately in both operating modes based on the capacity or running cost of the Distributed Generators (DGs). The global information (such as the average voltage and output active power of the MG and so on) required by the proposed droop control method to restore the voltage and frequency deviations can be acquired distributedly based on the Multi Agent System (MAS). Simulation studies in PSCAD demonstrate the effectiveness of the proposed control method.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.607-618
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• 2022

This study involves the development of a Hwangto permeable block for rainwater storage tanks. The permeable products that form continuous voids between Hwangto binders and aggregates are fine milled slag powder, which is an industrial by-product generated during the production of Hwangto and iron, and ferro nickel slag. The properties of Hwangto permeable blocks were studied using recycled resource aggregates. The target quality is based on KSF 2394. The Hwangto permeable block for a rainwater storage tank is made of water-permeable material, and the permeability of the Hwangto permeable block itself is 0.1mm/sec or higher, with a physical performance of over 5.0MPa in flexural strength and over 20.0MPa in compressive strength. The physical properties of Hwangto permeable block for rainwater storage tanks were researched and developed. In order to prevent flooding due to heavy rain in summer and the urban heat island phenomenon due to depletion of ground water, continuous pores are formed in the block to secure a permeability function to prevent rainwater from accumulating in the pavement of the floor, and to prevent slippage for comfortable and safe storage.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.61-69
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• 2023

As global trade and maritime port environments change, the need to respond to larger and faster ships is increasing. Accordingly, new ports are being built around metropolitan cities such as Busan and Ulsan. In general, a compaction method using sand or gravel is applied to the construction of a new port. However, due to the lack of sand or gravel and the difficulty in securing economic feasibility due to the increase in unit price, the deep mixing method has recently been used. Therefore, in this study, CMD-SOIL using circulating resources was applied to the Ulsan area, and the applicability was determined by analyzing the laboratory mixing test and boring results at in-situ. As a result of the test, it was analyzed that it showed more than the design mixing strength, and it was possible to secure the similar performance as blast furnace slag cement. In addition, it was analyzed that the design standard strength can be sufficiently secured as a result of in-situ boring. Therefore, considering the field applicability in the Ulsan, it is judged that the use of CMD-SOIL is possible.