• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.593-599
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• 2017

In order to enhance ultra battery performances, the electrochemical characteristics of nano Pb/AC anode composite was investigated. Through nano Pb adsorption onto activated carbon, nano Pb/AC was synthesized and it was washed under vacuum process. The prepared anode materials was analysed by SEM, BET and EDS. The specific surface area and average pore size of nano Pb/AC composite were $1740m^2/g$ and 1.95 nm, respectively. The negative electrode of ultra battery was prepared by nano Pb/AC dip coating on lead plate. The electrochemical performances of ultra battery were studied using $PbO_2$ (the positive electrode) and prepared nano Pb/AC composite (the negative electrode) pair. Also the electrochemical behaviors of ultra battery were investigated by charge/discharge, cyclic voltammetry, impedance and rate capability tests in 5 M $H_2SO_4$ electrolyte. The initial capacity and cycling performance of the present nano Pb/AC ultra battery were improved with respect to the lead battery and the AC-coated lead battery. These experimental results indicate that the proper addition of nano Pb/AC into the negative electrode can improve the discharge capacity and the long term cycle stability and remarkably suppress the hydrogen evolution reaction on the negative electrode.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.111-122
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• 2013

Sodium sulfur (NAS) battery is a high energy storage system (ESS). These days, as the use of renewable green energy like wind energy, solar energy and ocean energy is rapidly increasing, the demand of ESS is increasing and NAS battery is considered to be one of the most promising ESS. Since NAS battery has a high energy density(3 times of lead acid battery), long cycle life and no self-charge and discharge, it is a good candidate for ESS. A NAS battery consists of sulfur as the positive electrode, sodium as the negative electrode and ${\beta}$"-alumina as the electrolyte and a separator simultaneously. Since sulfur is an insulator, carbon felt should be used as conductor with sulfur and so the composition and property of the cathode could largely influence the cell performance and life cycle. Therefore, in this paper, the composition of NAS battery, the property of carbon felt and sodium polysulfides ($Na_2S_x$, intermediates of discharge), and the effects of these factors on cycle performance of cells are described in detail.

• Journal of Power Electronics
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• v.11 no.1
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• pp.1-9
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• 2011

This paper describes a two quadrant bidirectional soft switching converter for ultra capacitor interface circuits. The total efficiency of the energy storage system in terms of size and cost can be increased by a combination of batteries and ultra capacitors. The required system energy is provided by a battery, while an ultra capacitor is used at high load power pulses. The ultra capacitor voltage changes during charge and discharge modes, therefore an interface circuit is required between the ultra capacitor and the battery. This interface circuit must have good efficiency while providing bidirectional power conversion to capture energy from regenerative braking, downhill driving and the protecting ultra capacitor from immediate discharge. In this paper a fully soft switched two quadrant bidirectional soft switching converter for ultra capacitor interface circuits is introduced and the elements of the converter are reduced considerably. In this paper, zero voltage transient (ZVT) and zero current transient (ZCT) techniques are applied to increase efficiency. The proposed converter acts as a ZCT Buck to charge the ultra capacitor. On the other hand, it acts as a ZVT Boost to discharge the ultra capacitor. A laboratory prototype converter is designed and realized for hybrid vehicle applications. The experimental results presented confirm the theoretical and simulation results.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.549-555
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• 2018

In this study, the electrochemical properties of nano-Pb/activated carbon (nano-Pb/AC) composites and electrolyte additives were examined to improve the performance of ultra batteries. Physical properties of the prepared nano-Pb/AC composites were analyzed using FE-SEM, TEM, XPS and BET. The electrochemical performances of ultra batteries were performed by cycle, rate performance and impedance tests. The cycling performance of nano-Pb/AC (Pb : 9 wt%) coated ultra battery increased by 150% with respect to the lead acid one, and the discharge specific capacity increased by 119-122% for 1-5 C rate tests. As a result of the impedance test, it was confirmed that the internal resistance decreased as the nano lead content increased. The cycle performance of the ultra battery containing 0.45 vol% electrolyte additives showed 140% longer than that of no electrolyte additives.

• Journal of Drive and Control
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• v.16 no.3
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• pp.16-22
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• 2019

Due to the rise in energy consumption and natural resource prices, the demand to improve energy efficiency in the construction machine has been highlighted. Even though many researchers have contributed to the development of the technology, CO2 gas emissions of heavy machinery remains high. One of the most significant problems of the novel excavator with internal combustion engines is the emission of harmful gas. To reduce emissions in the construction machine, it is necessary to replace the internal combustion engines with the alternative one. To overcome those problems, this paper focuses on the adoption of PEMFC hybrid engine for the excavator system. An internal combustion engine is replaced by new structures with fuel cell, battery and ultra capacitor. The proposed system has been designed and modeled using Simcenter Amesim software and compared with the conventional one through simulation results.

• Journal of Electrochemical Science and Technology
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• v.3 no.1
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• pp.14-23
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• 2012

Increasing demand of energy, the depletion of fossil fuel reserves, energy security and the climate change have forced us to look upon alternate energy resources. For today's electric vehicles that run on lithium-ion batteries, one of the biggest downsides is the limited range between recharging. Over the past several years, researchers have been working on lithium-air battery. These batteries could significantly increase the range of electric vehicles due to their high energy density, which could theoretically be equal to the energy density of gasoline. Li-air batteries are potentially viable ultra-high energy density chemical power sources, which could potentially offer specific energies up to 3000 $Whkg^{-1}$ being rechargeable. This paper provides a review on Lithium air battery as alternate energy resource for the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.454-461
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• 2007

The next-generation computer is the ultra-lightweight mobile computer that communicates with peripheral handhold devices and provides dynamically the services appropriate to user. To provide the dynamic services on the ultra-lightweight mobile computer, security problem for user or computer system information should be solved and security mechanism is necessary for the ultra-lightweight mobile computing environment that has battery limit and low performance. In this paper, the security mechanism on the component based middleware for the ultra-lightweight mobile computer was implemented using RC-5 cipher algorithm and SHA-1 authentication algorithm. The security components are dynamically loaded and executed into the component based middleware on the ultra-lightweight mobile computer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.11
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• pp.1615-1621
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• 2014

A wireless tram which runs without catenary and instead uses batteries installed in the tram has been recently researched actively. This paper presents a new method maximizing absorption of regenerative energy of a wireless tram and extending life cycle of the energy storage device in the wireless tram by applying line-optimized charging and discharging scenario. Energy efficiency and life cycle of energy storage system (ESS) are highly dependent on the characteristic of operating conditions. For example, frequent charge and discharge with high power cause the problems that decrease the battery life cycles. Hybrid energy storage system (HESS) is combination of two ESSs which have complementary characteristics to each other. HESS can provide even better functionality and performance than the battery only ESS due to the synergy effect of two ESSs. This paper also provides a power distribution strategy and driving scenarios which increase the life cycle and energy efficiency of the HESS consisting of a battery and an ultra-capacitor. The developed strategy was tested and verified by a hardware-in-the-loop-simulation (HILS) system which emulates the a wireless tram.

• Journal of Environmental Health Sciences
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• v.41 no.6
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• pp.412-424
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• 2015

Objectives: An ultra dry air environment of nearly ${\leq}2%$ RH is often required in lithium battery factories. The objective of this study is to evaluate the subjective eye, pulmonary, nose, and skin symptoms of workers exposed to ultra-low relative humidity and thionyl chloride. Methods: We recruited 274 workers using a self-reported questionnaire in March 2014. Those who worked in ultra-low relative humidity and with thionyl chloride were identified and their prevalence of symptoms was compared with that of other workers. We excluded white collar workers, researchers and other workers who were exposed to various hazard factors, and finally included 164 workers. Results: There were significant differences in the rate of self-reported eye and skin symptoms between exposure group_1 and exposure group_2. Exposure group_2 experienced more frequent eye, and skin symptoms. Multinomial logistic regression analysis for experience of dry eye symptoms and skin symptoms in exposure group_2 showed that dry eye symptoms (odds ratio [OR], 6.33, 95% confidence interval [CI], 2.19-18.24, p<0.001), and itchiness (OR, 6.45, 95% CI, 1.94-21.43, p<0.01) were the significant variables. The complaints of workers experiencing ultra-low relative humidity and thionyl chloride were high compared with other workers. Conclusion: These findings suggest that exposure to ultra-low relative humidity and thionyl chloride may be associated with more frequent eye and skin symptoms than exposure to ultra-low relative humidity alone. The current precautions to protect workers from the adverse effects of ultra-low relative humidity and thionyl chloride appear to be insufficient, indicating that additional management plans to reduce symptoms should be considered.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.225-232
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• 2013

In this paper, the study was conducted on the subject of the hybrid electric vehicles used by the military, and optimized the propulsion system for fuel economy considering energy supply to the mission equipments. For the analysis of the vehicles, a method based on the geometry and some assumptions was applied with basic vehicle dynamics. The sources of energy supply in the military hybrid electric vehicles are an engine, a battery and an ultra-capacitor. The optimal operation point among an engine, a battery and an ultra-capacitor can be found by minimizing energy consumption of driving power train and mission equipments. In the study, it was possible to find the optimal propulsion system by comparing fuel efficiency of the vehicles during the driving cycle.