• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.207-221
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• 2014

Recently, due to global warming, climate change has affected short time concentrated local rain and unexpected heavy rain which is increasingly causing life and property damage. Therefore, this paper studies the characteristic of localized heavy rain and flash flood in Nakdong basin study area by applying Data Mining method to predict flood and constructing water level predicting model. For the verification neural network from Data Mining method and hydraulic flood routing was used for flood from July 1989 to September 1999 in Nakdong point and Iseon point was used to compare flood level change between observed water level and SAM (Slope Area Method). In this research, the study area was divided into three cases in which each point's flood discharge, water level was considered to construct the model for hydraulic flood routing and neural network based on artificial intelligence which can be made from simple input data used for comparison analysis and comparison evaluation according to actual water level and from the model.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.3-15
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• 2008

This study aims to simulate the 3 dimensional (3D) model of Keum-man connection canal using geographic information system (GIS) as well as considering design in viewpoint of engineering. The canal connects from Keumkang to Mangyungkang in order to supply fresh water into Saemankeum lake. This study used 3 dimensional spatial planning model (3DSPLAM) process to generate the 3D model, which has not only several planning layers in actual process, but also their corresponding layers in modeling process to simulate 3D space of rural villages. The discharge of the canal is $20m^3/s$ on slope of 1/28,400 in the canal length of 14.2km, which consists of pipe line and open channel. This study surveyed the route of the canal and its surrounding environment for facilities to make images in the 3D graphic model. Besides, the present study developed data set in GIS for geogrphical surface modeling as well as parameters in hydraulic analysis for water surface profile on the canal using HEC-RAS model. From the data set constructed, this study performed analysis of water surface profile with HEC-RAS, generation of digital elevation model (DEM) and 3D objects, design of the canal section and route on DEM in AutoCAD, and 3D canal model and its surrounding 3D space in 3DMAX with virtual reality. The study result showed that the process making 3D canal model tried in this study is very useful to generate computer graphic model with the designed canal on the surface of DEM. The generated 3D canal can be used to assist decision support for the canal policy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3480-3486
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• 2009

This research was based on the purpose of establishing predicted model of prematurely discharged patients using the mandatory information data, recorded in the medical institutes based on discharged patients of a University Hospital for the period of 1 year, from July. The result showed that the regression analysis model was the most excellent method of application model for preventing discharged patients, and when this is applied to discharged patients who are outpatients, the possibility of discharge can be less than staying in the emergency room. In addition, based on threshold 0.7, when we expect the discharged patients, out of 920 discharged patients, the actual patients who are discharged can become 136, showing the extract effectiveness of 14.78%. Based on the perspective of lift value, compared to random extract, this is 2.9 times (14.78/5.15) more effective.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.84-91
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• 2014

The flow rate control of a cavitating venturi has been investigated with downstream pressure variation. A set of cavitating venturies for a liquid rocket engine thrust chamber firing test facility have been designed and manufactured. The flow characteristics of the cavitating venturies have been analyzed by experimental and computational methods. Results showed that constant mass flow rate condition was established by the cavitation inside the venturi. However, upstream pressure less than the actual design pressure of the cavitating venturi could not supply a constant flow rate.

• Corrosion Science and Technology
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• v.7 no.1
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• pp.16-21
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• 2008

A non-phosphorous program employing an alkyl epoxy carboxylate (AEC) has been successfully applied to petrochemical and other large industrial open recirculating cooling water systems. AEC is a patented non-phosphorous calcium carbonate scale inhibitor that has demonstrated better scale inhibition abilities than traditional organic phosphonates. In addition to its antiscalant properties, AEC inhibits carbon steel corrosion when used at high dosages. AEC can be combined with zinc to form a non-phosphorous program with very low levels of phosphate to provide an environmentally acceptable program. In actual applications, the total phosphate developed in the cooling system from cycling the makeup is below 1 ppm as $PO_4$. This level has complied with the highest standards of wastewater discharge limitations. The performance of two AEC/Zinc applications is reviewed. In both cases excellent corrosion and scale control were achieved with AEC/Zinc programs. One case history details the performance with a low hardness water (100 ppm calcium, as $CaCO_3$) operating at 8-10 cycles of concentration. The corrosive nature of the water and the long retention time of the system stressed both the corrosion and scale control capabilities of the program. The second case history demonstrates the performance of the program with a moderate hardness water (400-600 ppm calcium, as $CaCO_3$), but under harsh conditions of high temperature and low flow. The AEC/zinc combination has been found to be highly effective in controlling the corrosion of ferrous metals. AEC can provide good corrosion inhibition at high concentrations, while zinc is known to be an excellent cathodic inhibitor. The combination of the two inhibitors not only provides a synergistic blend that is effective over a wide range of operating conditions, but also is environmentally friendly.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.15-23
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• 2013

In this study, thermodynamic performance of R435A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 20%R152a/80%RE170 using actual domestic water purifiers. This mixture is numbered and listed as R435A by ASHRAE recently. Test results show that the system performance with R435A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R435A is 11.8% lower than that of HFC134a. The compressor discharge temperature of R435A $8^{\circ}C$ lower than that of HFC134a at the optimum charge. Overall, R435A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.

• Journal of the Korean Society for Railway
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• v.18 no.4
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• pp.325-334
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• 2015

This paper deals with a control method for a hybrid energy storage system (ESS) with a battery and super capacitor for grid-connected operation. To improve the grid regulation and to minimize the depth of discharge of the battery, control algorithms for the hybrid ESS are proposed. A p-q control with predictive current control is used for the inverters for the super-capacitor and the battery. To verify the effectiveness of the proposed control method, simulation studies using the PSIM and RTDS are carried out for the actual grid model.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.31-36
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• 2011

This paper investigates the ESD robustness of the stacked output driver with a 0.13um CMOS process. To represent an actual I/O system, we implemented stacked output driver circuits with pre-drivers and a rail-based power clamp. We implemented eight kinds of circuits varying pre-driver input connections and stacked driver size. The test circuits are examined with TLP measurements. It is shown that breakdown current and voltage can be increased by connecting the pre-driver input to a power supply and using stacked devices of a similar size. Based on the test results, design guideline is suggested to improve ESD robustness of the stacked output drivers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.2
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• pp.109-117
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• 2009

In this study, thermodynamic performance of R430A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 76%R152a124% R600a using actual domestic water purifiers. This mixture is numbered and listed as R430A by ASHRAE recently. Test results show that the system performance with R430A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC 134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a at the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.

• Journal of Korea Water Resources Association
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• v.43 no.3
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• pp.283-294
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• 2010

The objective of this study is to develop an accurate and stable dynamic water quality model which is capable of reflecting various flows and irregular cross sections and handling numerical oscillations under the low flow conditions. In order to solve the oscillation problem under the low flow conditions, diffusive wave method was applied to the low flow condition in developing a hydraulic model, DyHYD. DyQUAL is also developed as a water quality model to calculate up to 12 water quality variables including autochthonous BOD, water temperature, DO, TN and TP. The developed model is applied to both hypothetical river channels and actual Nakdong river watershed. Additionally, the applicability and reliability of the models are verified by comparing simulation results with observed values. Nash-Sutcliffe coefficients are estimated by comparison between simulation results and observed values. In the calibration and verification process, the coefficients varies from 0.391 to 0.591 and 0.704 to 0.902 for discharge, BOD, TN and TP, respectively.