• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.44-48
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• 2000

Microbial fuel cells comprising the microorganism P. vulgaris, thionin as a mediator, and various mono- and disaccharides in an anodic compartment have been developed. A cathodic compartment containing a Pt electrode and Fe$(CN)_6^{3-}$ was separated from an anode by the Nafion membrane. From absorbance-time measurements, it was found that the absorbance of thionin was not altered by the addition of P. vulgaris, even in the presence of sugars. However, thionin was effectively reduced when P. vulgaris was present. These results differ substantially from the case of safranine O, a phenazine-derivative, indicating that thionin takes up electrons during the metabolic oxidation processes of carbohydrates. Maximum fuel cell efficiency was observed at 37 $^{\circ}C$, optimum temperature for the growth of P. vulgaris, and 0.5 V cell voltage was obtained, which indicates that the metabolism of the microorganism directly affects the efficiency. Thionin concentration was closely related to cell performance. When the charging-discharging characteristics were tested with glucose, galactose, sucrose, maltose, and trehalose as carbon sources, galactose was found to give the highest coulombic efficiency. Cell performance was almost fully recovered with only small degradation when glucose and sucrose were used in the repetitive operation. Current was maintained nearly twice as long for sucrose than in the case of glucose.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.779-783
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• 2018

In this work, Mathematical modeling was carried-out to predict the charging/discharging characteristics of VRLA (Valve regulated lead acid) battery, which is mainly used as a 12 V lead acid battery for automobile. And It also carried-out how it's characteristics would be changed due to aging. A mathematical modeling technique, which has been mainly used to predict behavior of Lithium-ion batteries, is applied to commercial 70 Ah VRLA battery. The modeling result of Voltage was compared with result of constant current charge / discharge test. From this, it can be seen that the NTGK model can be applied to the lead acid battery with high accuracy. It was also found that the aging of lead-acid battery can be predicted by using it.

• Journal of the Korean Electrochemical Society
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• v.21 no.4
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• pp.68-79
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• 2018

Currently, hybridization of energy generator and storage devices is considered to be one of the most important energy-related technologies due to the possibility of replacing batteries or extending the lifetime of a batteries in accordance with increasing battery demand. This review aims to describe current progress on the mechanical energy generator and hybridization of energy generator and energy storage devices for self-powered electronics. First, the research trends related to energy generation devices using piezoelectric and triboelectric effect that convert physical energy into electric energy is introduced. In addition, integration of energy generators and energy storage devices is introduced. In particular, self-charging energy cells provide an innovative approach to the direct conversion of mechanical energy into electrochemical energy to decrease energy conversion loss.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.26-30
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• 2018

The turn-to-turn contact resistance of 2G high temperature superconducting (HTS) coils with metal insulation (MI) is closely related to the stability of the coils, current charging rate and delay time [1]. MI coils were fabricated using five kinds of metal tapes such as aluminum (Al) tape, brass tape, stainless steel (SS) tape, copper (Cu)-plated tape and one-sided Cu-plated SS tape. The turn-to-turn contact surface resistances of co-winding model coils using Al tape, brass tape, and SS tape were 342.6, 343.6 and $724.8{\mu}{\Omega}{\cdot}cm^2$, respectively. The turn-to-turn contact resistance of the model coil using the one-sided Cu-plated SS tape was $ 248.8{\mu}{\Omega}{\cdot}cm^2$, which was lower than that of Al and brass tape. Al or brass tape can be used to reduce contact resistance and improve the stability of the coil. Considering strength, SS tape is recommended. For strength and low contact resistance, SS tape with copper plating on one side can be used.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.519-528
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• 2019

Current brake system changes the kinetic energy into heat energy by friction-type of brake that the braking action is diverging into the air. The system has a device called a retarder that generates braking force. High-tech research on the high-speed response characteristics of retarders utilizing part of the braking energy of the retarder to save electrical energy consumption is already underway in advanced countries. In this paper, we propose DC-DC converter which converts 3-phase voltage generated from retarder to 24V DC voltage for battery charging and verify its validity through experiments.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.113-118
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• 2020

Recently, eco-friendly electric motorcycles have been considered to replace aging gasoline motorcycles to reduce the amount of suspended fine dust in air. However, existing rechargeable battery-powered electric motorcycles have been found unacceptable by users because of their many limitations, such as long charging time, short travel distance per charge, and low driving speed. To overcome the drawbacks of conventional electric motorcycles, this paper proposes an exchangeable battery-powered electric motorcycle and a new frame shape for housing the exchangeable battery. The proposed frame is similar to that of current electric motorcycles; however, the shape and position of the saddle support, battery, and controller mount section are redesigned. The safety of the presented frame is verified through static and dynamic analyses using ABAQUS. In particular, the dynamic analysis is conducted under the most extreme condition among the various operating situations, thus confirming the robustness of the proposed frame design.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.311-321
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• 2022

The report reviews recent research efforts in demonstrating a computing system whose operation principle mimics the dynamics of biological neurons. The temporal variation of the membrane potential of neurons is one of the key features that contribute to the information processing in the brain. We first summarize the neuron models that explain the experimentally observed change in the membrane potential. The function of ion channels is briefly introduced to understand such change from the molecular viewpoint. Dedicated circuits that can simulate the neuronal dynamics have been developed to reproduce the charging and discharging dynamics of neurons depending on the input ionic current from presynaptic neurons. Key elements include volatile memristors that can undergo volatile resistance switching depending on the voltage bias. This behavior called the threshold switching has been utilized to reproduce the spikes observed in the biological neurons. Various types of threshold switch have been applied in a different configuration in the hardware demonstration of neurons. Recent studies revealed that the memristor-based circuits could provide energy and space efficient options for the demonstration of neurons using the innate physical properties of materials compared to the options demonstrated with the conventional complementary metal-oxide-semiconductors (CMOS).

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.256-262
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• 2021

A carbon felt electrode was prepared using ozone and ammonia sequential treatment and applied as an electrode for a vanadium redox flow battery (VRFB). The physical and electrochemical analyses demonstrate that the oxygen groups facilitate nitrogen doping in the carbon felt. Carbon felt (J5O3+NH3), which was subjected to ammonia heat treatment after ozone treatment, showed higher oxygen and nitrogen contents than carbon felt (J5NH3+O3), which was subjected to ammonia heat treatment first and then ozone treatment. From the charging/discharging of VRFB, the J5O3+NH3 carbon felt electrode showed 14.4 Ah/L discharge capacity at a current density of 150 mA /cm², which was 15% and 33% higher than that of J5NH3+O3 and non-activated carbon felt (J5), respectively. These results show that ozone and ammonia sequential treatment is an effective carbon felt activation method to increase the performance of the vanadium redox flow battery.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.231-242
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• 2023

Li₂O-based cathodes utilizing oxide-peroxide conversion are innovative next-generation cathodes that have the potential to surpass the capacity of current commercial cathodes. However, these cathodes are exposed to severe cathode-electrolyte side reactions owing to the formation of highly reactive superoxides (O^x-, 1 ≤ x < 2) from O^2- ions in the Li₂O structure during charging. Succinonitrile (SN) has been used as a stabilizer at the cathode/electrolyte interface to mitigate cathode-electrolyte side reactions. SN forms a protective layer through decomposition during cycling, potentially reducing unwanted side reactions at the interface. In this study, a composite of Li₂O and Ni-embedded reduced graphene oxide (LNGO) was used as the Li₂O-based cathode. The addition of SN effectively thinned the interfacial layer formed during cycling. The presence of a N-derived layer resulting from the decomposition of SN was observed after cycling, potentially suppressing the formation of undesirable reaction products and the growth of the interfacial layer. The cell with the SN additive exhibited an enhanced electrochemical performance, including increased usable capacity and improved cyclic performance. The results confirm that incorporating the SN additive effectively stabilizes the cathode-electrolyte interface in Li₂O-based cathodes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.102-109
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• 1987

This study is carrier out to investigate the carrier injection and the characteristics of trapping for the CVD deposited Al2O3 film on Si substrates. Samples used are metal -Al2O3-Si Structure in which metal field plates are used with Aluminium or God. Canier injection and trapping, which result in flat band voltalge shift, occur at fields as low as 1~2 MV/cm. An approximate method is proposed for computing the location of the centroid of the trapped electrons in this paper. Results show that carriers are trapped near the injecting interface at fields less than about 5MV/cm. Because of continued charging, a steady state can not be reached. Therefore the unique I-V curve is obtained when the traps are initially empty. By utilization of applied voltage on each point of the fresh device sample, it is measured the I-V surves for two polarities of applied voltage. The current densities observed in the Al2O3 films are much larger than those obtained in SiO2.