• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.299-302
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• 2009

Oxygen ionic conductors of YSZ electrolyte in SOFC unit cell are applied to anode and cathode as well as electrolyte to have triple-phase-boundaries(TPB) of electrochemical reaction, and it is required to decrease the sintering temperature of anode-supported electrolyte by the nanoscale of YSZ powder.In this report, nanoscale YSZ powder was synthesized by the chemical co-precipitation method. The particle size, surface area and morphology of the powder were observed by SEM and BET. Thin film electrolyte of under 10㎛ was fabricated by tape casting using the synthesized YSZ powder, and ionic conductivity and gas permiability of electrolyte film were evaluated. Finally, the SOFC unit cell was fabricated using the anode-supported electrolyte prepared by a tape casting method and co-sintering. Electrochemical evauations of the SOFC unit cell, including measurements such as power density and impedance, were performed and analyzed.

• Journal of the Korean Ceramic Society
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• v.30 no.9
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• pp.717-722
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• 1993

Effects of microstructures on the electrical properties of ZrO2 based ceramics were analyzed by modeling layer arrangements and mixed phase structures. Single layers and alternating multilayers were made from 3mol% and 8mol% Y2O3 doped ZrO2 powders, while mixed specimen was made by blending and compacting these raw powders. After sintering at 150$0^{\circ}C$ for 2hr in air, AC impedance characteristics were measured. Contributiion of bulk comonent to total resistivity and its temperature-dependence were larger in 8Y-ZrO2 single layer than in 3Y-ZrO2 single layer. The multilayered specimen connected in serial to electrodes showed partial characteristics of both 3Y-ZrO2 and 8Y-ZrO2 single layers. The multilayered specimen connected in parallel to electrodes and the mixed specimen exhibited characteristics mainly of 8Y-ZrO2 single layer. The multilayered specimen connected in parallel to electrodes revealed the highest electrical conductivity near the operating temperature of solid oxide fuel cell. However, it is expected that the mixed specimen is appropriate for the applications because of its relatively high electrical conductivity with high strength expected.

• Composites Research
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• v.26 no.6
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• pp.373-379
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• 2013

The coating of metal surface with carbon nanotubes (CNTs) has been studied for the heat transfer enhancement of the boiling and condensation of refrigerant. The MWCNT/copper composite powder was made by the attrition ball milling, which has been coated on the copper wafer by electrostatic powder coating and sintered with electric furnace. In this paper, experiments were performed to assess the characterization and comparison of CNT before and after sinterning and the morphology changes of the CNT/Cu-coated surface. The samples were examined by the scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDAX) and raman spectroscopy. To verify the heat transfer enhancement, boiling heat transfer tests were performed.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.592-598
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• 2011

Electrode of solid oxide fuel cell must have sufficient porosity to allow gas transport to the interface with electrolyte effectively but high porosity has a negative impact on structural stability in electrode support. Thus, the upper limit of porosity is based on consideration of mechanical strength of electrode. In this study, the effect of microstructure of Ni-YSZ anode supported SOFC on the mechanical and electrical property was investigated. LSCF composite cathode and 8YSZ electrolyte were used. The porosity of the anode was modified by the amount of graphite powder and added graphite contents were 24, 18, 12 vol%, respectively. The higher the porosity, the better the electrical performance, $P_{max}$. While the flexural strength decreased with increasing the amount of graphite. But the rate of increase in electrical performance and the rate of decrease in mechanical strength were not directly proportional to amount of graphite. The optimum graphite content incorporating both electrical and mechanical performance was 18 vol%.

• Annual Conference of KIPS
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• 2019.10a
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• pp.133-136
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• 2019

차량에서 생성되는 데이터의 가치가 상승함에 따라 데이터 소스와 데이터 내용에 대한 보안 위협 또한 증가하고 있다. 데이터 소스인 차량의 경우에는 운행의 안정성을 보장하고자 블록체인을 결합하려는 시도가 있어왔지만, 무결한 차량 운행 데이터 관리 시스템에 대한 이해 부족으로 데이터 위·변조 등 차량 데이터에 대한 사이버 공격에 적절히 대응하지 못하고 있다. 이에 본 논문은 수집된 차량 데이터의 무결성을 보장하고 수집된 데이터에 대한 질의가 가능한 블록체인 기반 데이터 베이스 시스템을 제안한다. 본 시스템을 통하여 분산 합의 기반 데이터 무결성 검증, 블록을 구성하는 해시트리의 복제 저장 없이 위·변조된 차량 데이터 검출, 일정 수준의 장애를 허용한 상태 하에서의 질의문 처리 등이 가능해진다. 본 시스템은 높은 공간 효율성과 확장성을 가지며, 수소전기차 공유 업체의 차량 운행 정보를 바탕으로 한 성능 평가 결과 평균적으로 데이터 블록 저장에 4.0 초, 각 블록 검증에 2.4 초, 질의 처리를 위한 합의 과정에 1.3 초가 소요됨을 확인하였다.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.11-16
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• 2019

Ni-benzene-1,3,5-tricarboxylic acid based metal organic frameworks were successfully synthesized by hydrothermal method and thermally treated at various temperature. The electrochemical performance of composites was investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Among all prepared composites, the samples annealed at $250^{\circ}C$ showed the highest capacitance with a low resistance, and high cycle stability. It was possible to obtain the low electrical resistance and high electric conductivity of the electrode by improved microstructure and morphology after the thermal annealing at $250^{\circ}C$. The samples annealed at $250^{\circ}C$ also displayed the maximum specific capacitance with a value of $953Fg^{-1}$ at a current density of $0.66A/g^{-1}$ in 6 M KOH electrolyte. Moreover, a 86.4% of the initial specific capacitance of the composite was maintained after 3,000 times charge-discharge cycle tests. Based on these properties, it can be concluded that the composite could be applied as potential supercapacitor electrode materials.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.5
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• pp.21-32
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• 2024

This paper proposes a smart safety system that combines low-cost CW(Continuous Wave) radar and IMU sensors to enhance blind spots that pose safety risks to workers in industrial manufacturing environments. The system employs a 24 GHz radar and a 6-axis IMU sensor to detect worker movements and utilizes a machine learning model to recognize worker situations in vibrating manufacturing sites. The ensemble boosting tree-based model achieved over 92.8% worker detection accuracy, demonstrating its effectiveness in improving safety in industrial settings.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.35-42
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• 2000

In this paper, AE(Acoustic Emission) signals detected from the growth of the electrical tree in an epoxy resin under ac high-voltage application were analysed to diagnose the insulation deterioration of cast-resin power transformer. Frequency spectra of AE signals generated from the magnetizing and the load currents in the actual operating cast-resin power transformer of 500[kVA] under distribution system of 22.9[kV] were also analysed to distinguish the AE signals due to void discharges from the magnetic circuit noises in the core of the transformer. As the experimental results, we could distinguish the AE signals whether those signals were caused due to the void discharges or due to the magnetic circuit noises by analyzing the frequency spectrum of AE signals. The frequency spectra of AE signals generated from the cast-resin power transformer in operation due to both the magnetizing and the load currents appeared in the range of 40-120[kHz], but the frequency band of AE signals emitted from the void discharges in an epoxy resin sample was about 50[kHz] to 230[kHz].

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.44-50
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• 1992

The ability to account for magnetic and spectra properties of complexes was investigated for the splitting of the degenerate d-orbitals and with nonaqueous solution by UV/vis-spectrophotometric method. The correlation of the magnetitude of 10Dq obtained from the spectra, the pairing energy, and the spin state of the complexes. The electrochemical behavior of complexes were investigated by the use of cyclic voltammetry in aprotic media. These reduction peak of $[(C_6H_5)3_P]_2Pd(II)(CH_3COO)_2$ and $[(C_6H_5)_3Pd]_2Pd(II)Cl_2$ were irreversible one-electron processes at peak $E_{pc1} = -1.32 V,\;E_{pc2} = -1.56 V$ and $E_{pc1} = -1.74 V,\;E_{pc2} = -1.88 V$ of these complexes vs. Ag/AgCl, but nickel complexes were not to be reducible.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.89-93
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• 2004

Sulfonated polysulfone (SPSF) with poly(phenylmethyl silsesquioxane, PPSQ) composite polymer electrolyte membranes were prepared and their proton conductivity, water uptake and methanol permeability of membranes were characterized. By controlling the ratio of $(CH_3)_3SCI\;and\;CISO_3H$ and reaction time, SPSF with $37\~75\%$ degree of sulfonation were synthesized. The increase of sulfonate groups in the base polymer resulted in the increase of the water uptake in the membranes as well as methanol permeability. Composite membranes were prepared by casting of DMF solution of SPSF and PPSQ. The proton conductivity of the composite membrane at room temperature was $2.8\times10^{-3}\~4.9\times10^{-2}S/cm.$ The increase of PPSQ contents in composite membranes resulted in a decrease in water uptake and methanol permeability. Composite membranes containing $5\%$ PPSQ did not make a significant effect on the proton conductivity nO methanol permeability compared with that of pristine SPSF, but a significant decrease of water uptake was observed.