• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.617-621
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• 2016

In addition to the energy storage facilities based on high power technologies, Electric double layer capacitors(EDLC) are today's candidate for power quality stabilization. However, its low energy density is often inhibiting factor for application of electric power industry. Hybrid supercapacitor is an promising energy storage device that positioned between conventional EDLC and Li-ion battery. This paper describes the preparation and characteristics of a hybrid supercapacitor and module for power quality stabilization. A cylindrical 3200F hybrid supercapacitor ($60{\times}74.5mm$) was assembled by using the $Li_4Ti_5O_{12}$ electrode as an anode and activated carbon as a cathode. It shows 2.5 times higher energy density than conventional EDLC with the same volume. In order to determine the characteristics of the hybrid supercapacitor Module for uninterruptible power supply (UPS), hybrid supercapacitor cells were connected in series with active balancing circuit. At even the high current density of 14A(10C), Module prepared by 18 cells showed the capacitance of 170F at 30~50V, suggesting the applicability for UPS.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1740-1744
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• 2017

This paper describes the preparation and characteristics of a battery capacitor and module for solar power system. A cylindrical 30,000F battery capacitor ($60{\times}138mm$) was assembled by using the $LTO(Li_4Ti_5O_{12})$ electrode as an anode and $NMC(LiNiMnCoO_2)-LCO(LiCoO_2)$ as a cathode. The battery capacitor has reduced energy density and power density under high CC(constant current) and CP(constant power) conditions. Battery capacitor module (16V, 11Ah) was fabricated using an asymmetric hybrid capacitor with a capacitance of 30,000F. In order to determine the characteristics of the battery capacitor Module for solar power system, battery capacitor cells were connected in series with active balancing circuit. As a result of measuring the 100w LED lamp, it was discharged at the voltage of 15V~10V, and the compensation time at discharge was measured to be about 4979s. Experimental results show that it can be applied to applications related to solar power system by applying battery capacitor module.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.309-313
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• 2024

The key to determining the lifetime of OLED device is how much brightness can be maintained. It can be said that there are internal and external causes for the degradation of OLED devices. The most important cause of internal degradation is bonding and degradation in the excited state due to the electrochemical instability of organic materials. The structure of OLED modeled in this paper consists of a cathode layer, electron injection layer (EIL), electron transport layer (ETL), light emission layer, hole transport layer (HTL), hole injection layer (HIL), and anode layer on a glass substrate from top to bottom. It was confirmed that the temperature generated in OLED was distributed around the maximum of 343.15 K centered on the emission layer. It can be seen that the heat distribution generated in the presented OLED structure has an asymmetrically high temperature distribution toward the cathode, which is believed to be because the sizes of the cathode and positive electrode are asymmetric. Therefore, when designing OLED, it is believed that designing the structures of the cathode and anode electrodes as symmetrically as possible can ensure uniform heat distribution, maintain uniform luminance of OLED, and extend the lifetime. The thermal distribution of OLED was analyzed using the finite element method according to Comsol 5.2.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.214-221
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• 2001

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a $Ti:LiMbO_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1 V/cm to 60 V/cm at 60Hz through 100 kHz. Using a probe antenna of $10\;mm{\times}10\;mm$, the output voltage of $10^{-2}\;mV$ was measured with respect to the electric field strength of 0.1 V/cm at 60 Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.

• Applied Microscopy
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• v.18 no.2
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• pp.177-186
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• 1988

Degeneration of the axon terminals of mamillo-thalamic tract following the electrical coagulation of mamillary body is well known. In this study, the author investigated the ultrastructural alterations of neuropil components, initiated by terminal degenerations. Rats weighing approximately 250 gm were fixed on the stereotaxic instrument(David Kopf Inc., Heavy duty model), and NE 300 active electrode(Rhodes Med. Instr. Inc.) was introduced to the mamillary position of anterior 3.8 mm, lateral 0.5 mm, height 3.8 mm and lateral angle of $23^{\circ}$ according to De Groot's Atlas. Electric current of 20 mA was applied during 1 minute between active and inactive electrodes with Radio Frequency Lesion Generator(RFG 4, Radionics Inc.). Two hours, 2 days, 1 week and 2 weeks following the electrical coagulation of mamillary body, ipsilateral anterior thalamic nucleus was fixed in 1% glutaraldehyde-l% paraformaldehyde and 2% osmium tetroxide, embedded in Araldite mixture, cutted with LKB ultra tome V, stained with uranyl acetate-lead citrate and observed with JEOL 100 CX electron microscope. Observed results were as follows; 1. Degenerated mamillo-thalamic synapses were observed to form asymmetric axospinous or axo-dendritic types. 2. Terminal degeneration was not easily discernible at 2 hours interval after mamillary lesion, but following 2 days the terminal degeneration was apparent. 3. Postsynaptic spines, dendrites and even their cell bodies show edematic changes caused by the degeneration of postsynaptic counterpart. 4. Astrocytic territories, including perivascular processes forming glial limitans of blood-brain barrier, exhibit remarkable expansion. 5. Oligoglia and astroglia are actively engaged in the removal of degenerated elements. 6. Active forms of microglia were increased. 7. The observed results may represent typical ultrastructural alteration pattern within neuropil following the degeneration of certain input axon terminals.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.6
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• pp.1-7
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• 2002

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a Ti:LiNbO$_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1V/cm to 60V/cm at 60Hz through 100KHz. Using a probe antenna of 10mm$\times$10mm, the output voltage of 10㎷ was measured with respect to the electric field strength of 0.1V/cm at 60Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.

• KSBB Journal
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• v.10 no.4
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• pp.468-474
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• 1995

The disposable glucose bio-sensor using composite of CTA and PCL membrane was developed for measurement of glucose. The most effective membrane was composed of CTA/PCL(80/20, w/w) and glutaraldehyde one-step immobilization method ($10{\mu}m$ thickness) for glucose sensor gave the best result among various methods, considering oxygen permeability and electronic sensitivity. A scanning electron micrograph of the cross-section of a typical asymmetric CTA/PCL composite membrane showed that the membrane fused with a dense layer covered with a GOD-glutaraldehyde. Glucose oxidase immoblilized on the membrane showed the linearity between difference of absolute amperometric values and glucose concentrations within 7mM when the GOD immobilized electrode was used. About 35% of activity was remained after 8 days when the tyrosinase was immobilized on CTA/PCL (80/20) membrane.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.167-175
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• 2015

A retinal prosthesis is being developed for the restoration of vision in patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Determining optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we investigated the effects of different charge-balanced biphasic pulses with regard to their effectiveness in evoking retinal ganglion cell (RGC) responses. Retinal degeneration (rd1) mice were used (n=17). From the ex-vivo retinal preparation, retinal patches were placed ganglion cell layer down onto an $8{\times}8$ multielectrode array (MEA) and RGC responses were recorded while applying electrical stimuli. For asymmetric pulses, 1st phase of the pulse is the same with symmetric pulse but the amplitude of 2nd phase of the pulse is less than $10{\mu}A$ and charge balanced condition is satisfied by lengthening the duration of the pulse. For intensities (or duration) modulation, duration (or amplitude) of the pulse was fixed to $500{\mu}s$($30{\mu}A$), changing the intensities (or duration) from 2 to $60{\mu}A$(60 to $1000{\mu}s$). RGCs were classified as response-positive when PSTH showed multiple (3~4) peaks within 400 ms post stimulus and the number of spikes was at least 30% more than that for the immediate pre-stimulus 400 ms period. RGC responses were well modulated both with anodic and cathodic phase-1st biphasic pulses. Cathodic phase-1st pulses produced significantly better modulation of RGC activity than anodic phase-1st pulses regardless of symmetry of the pulse.

• Therapeutic Science for Rehabilitation
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• v.8 no.1
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• pp.41-50
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• 2019

Objective: The purpose of this study was to investigate whether there is a difference in the brain connectivity in mental practice and physical performance of training bilateral upper extremity function. Method: The subject performed activities involving mental tasks and physical exercise for bilateral upper extremity functioning during each phase of EEG measurements. The subject performed a symmetrical task(lifting a box and placing it back) that involved moving both arms at the same time and an asymmetrical task(opening and closing a bottle cap) in order to perform functional tasks. EEG electrodes were attached to Fp1, Fp2, F3, F4, T3, T4, P3, and P4. Data analysis was performed using Cross-Line Mapping for correlational analyses between EEG electrode pairs. Conclusion: This study found that the brain connectivity patterns of symmetrical and asymmetric upper extremity tasks have similar patterns for the motor and sensory area, and that the correlation of the physical practice is generally higher than that of the mental practice.

• Membrane Journal
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• v.33 no.4
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• pp.181-190
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• 2023

Wastewater purification is one of the most important techniques for controlling environmental pollution and fulfilling the demand for freshwater supply. Various technologies, such as different types of distillations and reverse osmosis processes, need higher energy input. Capacitive deionization (CDI) is an alternative method in which power consumption is deficient and works on the supercapacitor principle. Research is going on to improve the electrode materials to improve the efficiency of the process. A reverse electrodialysis (RED) is the most commonly used desalination technology and osmotic power generator. Among many studies conducted to enhance the efficiency of RED, MXene, as an ion exchange membrane (IEM) and 2D nanofluidic channels in IEM, is rising as a promising way to improve the physical and electrochemical properties of RED. It is used alone and other polymeric materials are mixed with MXene to enhance the performance of the membrane further. The maximum desalination performances of MXene with preconditioning, Ti₃C₂T_x, Nafion, and hetero-structures were respectively measured, proving the potential of MXene for a promising material in the desalination industry. In terms of osmotic power generating via RED, adopting MXene as asymmetric nanofluidic ion channels in IEM significantly improved the maximum osmotic output power density, most of them surpassing the commercialization benchmark, 5 Wm^-2. By connecting the number of unit cells, the output voltage reaches the point where it can directly power the electronic devices without any intermediate aid. The studies around MXene have significantly increased in recent years, yet there is more to be revealed about the application of MXene in the membrane and osmotic power-generating industry. This review discusses the electrodialysis process based on MXene composite membrane.