• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.156-162
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• 1999

Various types of iron oxide based materials as a cathode of lithium secondary battery have been prepared and their electrochemical characteristics have been also observed. In order to understand the fundamental characteristics of iron oxide electrode, three kinds of iron oxides such as iron oxides formed by direct oxidation of iron plate or iron powders and FeOOH powders were tested with cyclic voltammetry. The oxidation and reduction peaks due to the reaction of intercalation and deintercalation were not observed for the iron oxide prepared with iron plate and FeOOH powders. In case of iron oxide prepared from iron powders, only one reduction peak was observed. A layered form of $LiFeO_2$ was synthesized directly from $FeCl_3\cdot6H_2O,\;NaOH\;and\;LiOH$ and LiOH by hydrothermal reaction. The effect of NaOH on the electrode performance was examined. When increasing NaOH, it provides the electrode with less discharge capacity and efficiency, however, decreasing rate of discharge capacity became smaller. $LiFeO_2$ synthesized with the molar ratio of $NaOH/FeCl_3/LiOH$, 2/1/7 showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.388-394
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• 2004

LiCoO$_2$ as the cathode activity material for lithium secondary battery was prepared from a homogeneously mixed powder of LiNO$_3$/Co by SHS process under argon gas. The characteristics of powder including electrochemical properties were investigated according to various reaction conditions. The reaction temperature/velocity and the size of LiCoO$_2$ were controlled by Li/Co molar ratio and a cooling rate of the specimen, respectively. The maximum discharge capacity was 145 mAh/g on 1.05 Li/Co molar ratio and the relatively stable cycling characteristic with 6.4% of capacity fading was obtained after 10th charging-discharging test.

• Journal of Power Electronics
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• v.13 no.3
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• pp.429-436
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• 2013

Online simulations are utilized to reduce time and cost in the development and performance optimization of plug-in hybrid electric vehicle (PHEV) and electric vehicles (EV) systems. One of the most important factors in an online simulation is the accuracy of the model. In particular, a model of a battery should accurately reflect the properties of an actual battery. However, precise dynamic modeling of high-capacity battery systems, which significantly affects the performance of a PHEV, is difficult because of its nonlinear electrochemical characteristics. In this study, a dynamic model of a high-capacity battery cell for a PHEV is developed through the extraction of the equivalent impedance parameters using electrochemical impedance spectroscopy (EIS). Based on the extracted parameters, a battery cell model is implemented using MATLAB/Simulink, and charging/discharging profiles are executed for comparative verification. Based on the obtained results, the model is optimized for a high-capacity battery cell for a PHEV. The simulation results show good agreement with the experimental results, thereby validating the developed model and verifying its accuracy.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.279-286
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• 1998

The south-western part of Korea is situated in an unbalance of water supply and demand relating to the Keum, Mankyung, Dongjin and Youngsan River and their estuary reservoirs. For example, the Keum River estuary reservoir is discharging the larger amount of yearly runoff into the sea due to the small storage capacity, while Saemankeum estuary reservoir which is under construction, has the smaller runoff amount comparing with its storage capacity, And the downstream area of the Youngsan River, such as Youngkwang, Youngam are deficient in water due in larger demand and smaller supply. In order to solve the above unbalanced water supply and demand and also to improve the water use efficiency, the Hierarchical Operation Model for Multi-reservoir System(HOMMS) has been developed and applied to analyze the multi-reservoir operation assuming that the above reservoirs were linked each other. The result of this study shows that 2,148MCM of annual additional water requirement for agricultural and rural water demands are required in this region at 2011 of target year, and these demands can be resolved by diverting and reusing 1,913MCM of the released water from the estuary reservoirs into the sea.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.3
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• pp.59-64
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• 2011

The objective of the study is to develop life cycle inventory (LCI) database of dam, a major facility for irrigation water supply. The types of database developed are three out of nine dams according to the size of the wate r storage capacity: two kinds larger than 500,000 $m^3$ depending on gate for discharging (Type 1) and the other dam smaller than 500,000 $m^3$ (Type 2). According to the LCI analysis, type 1 larger than 500,000 $m^3$ storage capacity with gate has the lowest environment impact in the 6 impact categories. The impact of the type 1 accounts for 7~35 % of the type 2 for supplying irrigation water. Comparing with the environment impacts of water for other uses such as drinking and industrial water, the impacts of 1 $m^3$ irrigation water supply is 4~45 % of the one for industrial water supply and 1~16 % of the drinking water's. The three types of LCI DB on the irrigation water by dams will be useful in the application of Life Cycle Assessment in agricultural products and environmental labelling including carbon footprint since it is complied to the guidelines of LCI DB constr uction issued by Ministry of Environment and Ministry of Knowledge Economy.

• Journal of Environmental Science International
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• v.11 no.9
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• pp.945-954
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• 2002

The objective okgf this study is understanding and evaluation of temporal and spatial variation of pollutant loads by input sources for water quality management in Kamak Bay. Flow rate of rivers and ditches ranges from about $2,592-63,072m^3/d$ in October to $864-55,296m^3/d$ in January. In particular, the R2 predominated flow rate among input sources. Total COD, BOD, DIN and DIP loadings in January were about 896kg/d, 718kg/d, 2,152kg/d, and 154kg/d, respectively, which exceeded those of October. Lower POC/TOC levels are estimated in R2, and also in October. Temporal variation of pollutant loads were closely related to the human activity. Total discharging loadings of BOD, TN and TP by unit loading estimation were 4,993.0kg/d, 2,558.7kg/d, and 289.2kg/d, respectively, and were mainly affected by the population. Runoff ratio of BOD was about 0.14 in January Mean $NH_4^＋_-N$ and $PO_4\;^{3-}-P$ loadings from sediment were 16.23mg/$m^2$/d and 7.26mg/$m^2$/d, respectively. For the improvement of water quality in this area, not only pollutant loads of rivers and ditches but also benthic flux from sediment should be reduced within the limits of the environmental capacity.

• The KSFM Journal of Fluid Machinery
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• v.8 no.3 s.30
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• pp.16-25
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• 2005

The purpose of this study is localization of safety relief valves for Nuclear Service. The safety relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. We developed design technology used FEM ' CFM about safety relief valve for Nuclear Service according to ASME (or KEPIC) Code and KHNP's Technical Specification. To prove validity of a design technology, actually, we manufactured and inspected and tested the sample products designed according to a developed technology. The capacity qualification test was achieved according to requirement of ASME(or KEPIC) Code by NBBI and the functional qualification test was achieved according to ASME QME-1 for operating condition in technical specification of KHNP by NLI. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.97-105
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• 2008

This paper presents simulated and experimental test results of optimal control algorithm for an encapsulated ice thermal storage system with full capacity chiller operation. The algorithm finds an optimal combination of a chiller and/or a storage tank operation for the minimum total operation cost through a cycle of charging and discharging. Dynamic programming is used to find the optimal control schedule. The conventional control strategy of chiller-priority is the baseline case for comparing with the optimal control strategy through simulation and experimental test. Simulation shows that operating cost for the optimal control with chiller on-off operation is not so different from that with chiller part load capacity control. As a result from the experimental test, the optimal control operation according to the simulated operation schedule showed about 14 % of cost saving compared with the chiller-priority control.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.156-158
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• 2018

The inconsistencies between paralleled battery cells are becoming more considerable issue in high capacity battery applications like electric vehicles. Due to differences in state-of-charge (SOC) and internal resistance within individual cells in parallel, charging or discharging current is not appropriately balanced to each cell in terms of SOC, which may shorten the lifetime or sometimes cause safety issues. In this paper, an intelligent cell-balancing algorithm is proposed to overcome the inconsistency issue especially for paralleled battery cells. In this scheme, SOC information collected in the sub-BMS module is sent to the main-BMS module, where the number of parallel cells to be connected to DC bus is continuously updated based on the suggested SOC comparison rule. To verify the method, operation of the algorithm on 4 paralleled battery cells are simulated on Matlab/Simulink. The simulation result shows that the SOCs of paralleled cells are evenly redistributed. It is expected that the proposed algorithm provides high reliable and prolong the life cycle and working capacity of the battery pack.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.920-923
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• 2000

All solid-state thin film supercapacitor(TFSC) based on $RuO_2$ electrode was fabricated. Ruthenium oxide$(RuO_2)$ thin film was deposited on Pt/Ti/Si subsrate by d.c. magnetron sputtering. LiPON(lithium phosphorus oxynitride) thin film were deposited by r.f. reactive sputtering. X-ray diffraction patterns of $RuO_2$ and LiPON films revealed that crystal structures of both films were amorphous. To decrease resistivity of $RuO_2$ thin film, $RuO_2$ thin film was deposited with $H_2O$ vapor. In order to decide the maximum ionic conductivity, the LiPON films were prepared by various sputtering condition. The maximum ionic conductivity was $9.5\times{10}^7S/cm$. A charge-discharge measurements showed the capacity of $3\times{10-2}\;F/cm^2-\mu{m}$ for the as-fabricated TFSC. The discharging efficiency was decreased after 500 cycles by 40 %.