• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.627-640
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• 2001

Generally, the synthetic unit hydrograph method is presented to estimate the design flood in the ungaged watershed. However, due to the lack of rainfall-runoff data, the models developed in other countries such as U.S.A. and Japan have been widely used in Korea. Therefore, it may be essential to develope the rainfall-runoff model suitable for the hydrological char-acteristics in Korea. In this study, the representative unit hydrographs are derived from rainfall-runoff data at 19 basins in Selma-Cheon and 3-IHP experimental watersheds using ridge-regression method and Nash model. And a new synthetic unit hydrograph for Korea is suggested by integrating the described results and previous studies on unit hydrograph. The newly developed method is represented as two regression forms with three independent variables of watershed area, channel length, and channel slope by multiple regression analysis is carried out for each watershed, the coefficients of determination are not improved in all cases compared out for each watershed, the coefficients of determination are not improved n all cased the synthetic unit hydrograph for each watershed. Therefore, when the new method is applied to some watersheds, the result analyzed for all data has to be used.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.797-802
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• 2012

In this study, the potential performance enhancement in a dual heat pump system through series operation was investigated by a comparison between the performance for parallel and series operation for a heating supply temperature of $60^{\circ}C$. To compare the performance of each configuration fairly, the heat transfer surface area of the heat exchangers was fixed. The inlet temperatures and the flow rates of the heat source and the load were also fixed. In addition, the heat transfer and pressure drop characteristics of the working fluids were considered to achieve a more realistic comparison. The results show that the heating coefficient of performance (COP) of the series configuration is approximately 5% higher than that of the parallel configuration under the simulation conditions considered in the present study.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.3
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• pp.219-225
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• 2008

There are many problems in monitering environmental change around of nuclear power station, because interesting area is coastal and relatively large. The ground resolution of Landsat ETM+ imagery is high (30 m), but this imagery does not have enough informations for conducting atmospheric correction in evaluating sea surface temperatures. On the other hand, while it is possible to conduct atmospheric correction using MODIS imagery with it's two infrared bands, it's resolution is relatively low (1 km). Therefore, atmospheric corrected high resolution temperature information can be obtained from these two satellite images. In this study, digital numbers of Landsat ETM+ data in interesting area are georeferenced, converted to effective temperatures based on radiance value, and then the atmospheric correction is conducted using MODIS data. As a result, about $3.5^{\circ}C$ temperature differences were detected in comparing sea surface temperature of the surrounding area of Uljin nuclear power station with it of the same area located 5km far east.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.253-258
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• 2012

The effects of active sites and valence states were investigated over $Pd/TiO_2$ catalyst on simultaneous oxidation of $CH_4$ and CO. The Pd species (PdO) crystallite size increased with increasing Pd loadings, which results in enhancement of the activity of $CH_4$ oxidation. Different results from the activity of $CH_4$ and CO oxidation were shown to be dependent on the Pd valence state on the surface of the catalyst prepared through a thermal treatment. XRD and $H_2-TPR$ analysis confirmed that $Pd^{2+}$species was predominated in the calcination catalyst, while $Pd^0$species was predominated in the reduction catalyst. Additionally, it could be found that the valence state of Pd was a more important factor on the catalytic activity than that of factors as the surface area and pore volume. The reaction mechanism of $CH_4$ and CO followed by the valence state of Pd could be identified using FT-IR analysis.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.376-381
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• 2008

The deactivation of $V/TiO_2$ catalyst used in SCR (Selective Catalytic Reduction) using ammonia as a reductant to remove the nitrogen oxides (NOx) in the exhaust gas from fired power plant has been studied. The activity and surface area of the catalyst (Used-cat) which was exposed to the exhaust gas for long period have considerably decreased. The characterizations of these SCR catalysts were performed by XRD, FT-IR, FE-SEM, and IC/ICP. The crystal structure of $TiO_2$ both fresh and used catalyst has not been changed. However, $(NH_4)HSO_4$ deposited on the used catalyst surface verified from FT-IR, FE-SEM, and IC/ICP analysis. Moreover, the durability of $SO_2$ was increased by diminishing sulfate ($SO_4^{-2}$)f form.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.645-649
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• 2013

In this study, we investigated the $NH_3$ oxidation reaction characteristic over $W/TiO_2$ catalyst in order to control $NH_3$ generated from a thermoelectric power plant or incinerator. As a result, it was found that the optimal content of tungsten in $W/TiO_2$ catalyst is 10 wt% and $NH_3$ removal efficiency decreased due to decreasing specific surface areas of catalyst with increasing tungsten contents. When $NH_3$ was injected more than 420 ppm, $NH_3$ conversion decreased at the middle temperature range. In addition, $NH_3$ conversion decreased due to the competitive adsorption of moisture and with increasing oxygen concentration, the $NH_3$ conversion increased while the $N_2$ selectivity decreased.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.3
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• pp.51-57
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• 2007

In this study, We analyzed change of sea surface temperature due to cooling water around nuclear power station. Study area is around of Uljin nuclear power station, which is relatively large power station. There are many problems in monitering environmental change around of nuclear power station, because area is relatively large. We used Landsat 5, 7 Imagery which are useful in temperature analysis and can be easily obtained. After we georeferenced Landsat Imagery, radiance and sea surface temperature were calculated. As a result, As we compared sea surface temperature of surrounding area of nuclear power station with same area located 3 km east, there are $2.049^{\circ}C$ temperature difference.

• Journal of the Korean Solar Energy Society
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• v.34 no.1
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• pp.39-47
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• 2014

Solar applications analysis and building energy performance depend on the quality of the solar resource data available. Unfortunately, most of the weather stations do not measure solar radiation data in Korea, as a reason many researchers have studied different solar radiation estimation models and suggested to apply them to various locations in Korea. In addition, they also studied the impact of hourly global solar radiation on energy performance of an office building by comparing the simulated building energy consumptions using four different weather files, one using measured, and three estimated solar radiation from different models, which are Cloud-cover Radiation Model (CRM), Zhang and Huang Model (ZHM), and Meteorological Radiation Model (MRM), and concluded that there was some impact on energy performance of the building due to the using different solar radiation models. However, the result cannot be applied to all other buildings since the simulated office building for that study only used limited building characteristics such as using fixed values of solar heat gain coefficient (SHGC) and window-to-wall ratio (WWR), which are significant parameters related to solar radiation that affect to the building energy consumptions. Therefore, there is a need to identify how the building energy consumption will be changed by varying these building parameters. In this study, the impact of one measured and three estimated global solar radiation on energy performance of the office building was conducted taking account of SHGC and WWR. As a result, it was identified that the impact of four different solar radiation data on energy performance of the office building was evident regardless SHGC and WWR changes, and concluded that the most suitable solar models was changed from the CRM/ZHM to the MRM as SHGC and WWR increases.

• Journal of IKEEE
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• v.18 no.2
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• pp.263-271
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• 2014

This paper presents design of the second-order sigma-delta modulator for converting voltage and temperature signals to digital ones in Battery Management IC (BMIC) for mobile applications. The second-order single-loop switched-capacitor sigma-delta modulator with 1-bit quantization in 0.13-um CMOS technology is proposed. The proposed modulator is designed using switched-opamp technique for saving power consumption. With an oversampling ratio of 256 and clock frequency of 256kHz, the modulator achieves a measured 83-dB dynamic range and a peak signal-to-(noise+distortion) ratio (SNDR) of 81.7dB. Power dissipation is about 0.66 mW at 3.3 V power supply and the occupied core area is $0.425mm^2$.