• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.249-252
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• 2004

Chloride ion diffusion is the most important thing of occuring deterioration in RC structure. According to establish data, the curing time in concrete reduce the chloride ion diffusion coefficient. The purpose of this study is to make clear through experience on the effect of curing time on the chloride ion diffusion coefficient in concrete with Portland cement and ground granulated blast-furnance slag and a propose the standard of chloride ion diffusion coefficient in concrete.

• Information and Communications Magazine
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• v.33 no.7
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• pp.47-52
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• 2016

전기 자동차 및 신재생에너지 시장 확대로 EV, HEV, LEV 등 전기자동차의 수요가 증가함에 따라 2020년을 기점으로 백만개 이상의 리튬-이온 폐배터리가 생성될 것으로 예상되고 있다. 그러나 이러한 폐배터리는 잔여용량이 80%수준에서 교체되고 있어서 화학적 분해를 통한 재활용 이전에 안정적인 에너지저장장치로서 재사용할 수 있는 가능성을 보유하고 있다. 본고에서는 향후 지속적으로 발생이 예상되는 전기자동차의 폐배터리를 이용하여 에너지저장장치를 구성하는 방법에 대하여 다양한 다양한 국내외 기관들의 기술 및 연구동향에 대해 알아보고, 이를 바탕으로 효율적인 에너지저장장치 구성방법과 이를 확산하기 위한 사업화 방안 등을 알아본다.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.770-771
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• 2023

'환경친화적 자동차의 개발 및 보급 촉진에 관한 법률'에 따라 주거지역 내의 전기차 충전기 설치 및 보급이 빠르게 확산 중이다. 전기 자동차는 충전 중 화재 시 리튬이온 배터리 열폭주(thermal runaway) 현상 때문에 쉽게 진압하지 못한다는 단점이 존재한다. 이에 따라 지하 주차장에서의 전기 자동차 충전 중 화재 시 피해 최소화를 위한 스마트 IoT 주차장을 기획하고 개발하였다.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.614-623
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• 1993

Electrical characteristics of LiF-$Li_{2}O-B_{2}O_{3}-P_{2}O_5$ glasses with fixed $Li_2O$ content have been investigated by using AC impedance spectroscopy. Part of the total lithium ions present in these glasses contributes to conduction, and the changes in electrical conductivity with composition was inconsistent with the weak electrolyte model. The power law could not be used to determine the hopping ion concentration in these glasses. Both mobile carrier density and mobility have been modified as Li were added in the form of LiF. The formation of $(B-O-P)^-,di^-$, and metaborate group gave additional available sites for Li+ diffusion causing the enhancement of conductivity. The observed maximum conductivity was $2.43 \times 10^{-4}$S/cm at $150^{\circ}C$ at the composition containing 8mol% LiF. The decomposion potential amounted to 5.94V. The Li/glass electrolyte/$TiS_2$ solid-state cell showed open circuit voltage of 3.14V and energy density of 22 Wh/Kg at $150^{\circ}C$.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.999-1005
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• 1996

Pt catalyst on carbon black was prepared by colloidal method, ion exchanging method and methanol reducing method. The colloidal method has been used generally. At ion exchanging method, $H^+$ of functional group on carbon surface made by oxidation treatment was exchanged with Pt ion. At methanol reducing method, Pt was impregnated on carbon to reduce by methanol contained with surfactants. With TEM and XRD, Pt particle size impregnated on carbon by various methods was $30{\sim}50{\AA}$. Loading yield was about 100%, loading yield of ion exchanging method was 99.92% by DCP analysis and 99.87% by combustion method. Within 60 hour, current density of oxygen reduction was $460mA/cm^2$ at 0.7V(vs. RHE) at colloidal method. It was the better performance than catalyst prepared by ion exchanging, methanol reducing method. But, it was shown some decrease of performance for long operation time(after 100hour), catalyst prepared by methanol reducing method was shown stable performance.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.81-87
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• 1999

Poly-acrylonitrile (PAN) based carbon fibers were stabilized under various tensions in the presence of air at about $200^{\circ}C$ and sequentially carbonized under some different gas environments in the range of 700 to $1500^{\circ}C$. The prepared carbon fibers were used for rechargeable lithium ion battery anode to investigate preparation parameters effects on electrochemical characteristics. It was found that the tension during stabilization, carbonization temperature and gas atmospheres affect the carbon fiber properties such as conductivity, mechanical strength, surface morphology and diffusion coefficient of lithium ion, which are closely related to the on electrolchemical properties as well as the charge/discharge characteristics.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.114-121
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• 2016

This study investigates a CFD modeling of the charge-discharge behavior due to heat generation during charge-discharge cycles of a Li-ion secondary battery(LIB). Present LIB system adopted a current-density equation, heat and mass transfer governing equations upon the 1-dimensional system to the thickness direction for the rectangular pouch configuration. According to the 3-kinds of the charge-discharge current densities of 1C($17.5A/m^2$), 3C($52.5A/m^2$) and 5C($87.5A/m^2$) subject to a 3 V of cut-off voltage, a constant-temperature system at 298 K and three different heat generating systems were analyzed with comparison. Battery capacity decreases with increment of charge-discharge densities not only at the constant-temperature system but also at the heat-generating system. The time for charge-discharge cycles increases at the heat-generating system compare to the constant-temperature system. These trends are considered that the increase of temperature due to heat generation causes the decrement of equilibrium potential of electrodes and the increment of diffusivity of Li ions. Furthermore, cooling effects were discussed in order to control the influence of heat generation due to charge-discharge behavior of a Li-ion secondary battery.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.931-938
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• 2005

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the seawater. Because the damages of corrosion resulting from the chloride ion are very serious, many researches have been performed. Silver nitrate colormetric method that can measure easily penetration depth of chloride ion has been executed, recent)y. However, characteristics of silver nitrate colormetric method were not fully examined. Therefore, the objective of this paper Is to study the applicability of colormetric method. For the purpose of this, effect factors and reaction mechanism of colormetric method were investigated, and the colormetric method is applied for marine concrete structures. According to the results of silver nitrate colored method, two reactions such as white reaction of AgCl and brown reaction of AgOH were shown when $AgNO_3$ was sprayed in splited section. And velocity constant ratio(K) of two reactions appeared that white reaction, AgCl reacts with the fast speed by 3240. When the colormetric method was applied in concrete, it is reasonable that $AgNO_3$ solution more than 0.05N concentration was sprayed. It is confirmed that the colormetric method is useful tool for estimating the chloride of concrete structures in situ. The average chloride amount of colored parts indicates $0.9kg/m^3$ per concrete unit weight.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.461-470
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• 1994

Sorption experiments of $^{60}$ Co, $^{85}$ Sr. and $^{137}$ Cs onto sandstone particles in a batch were carried out to investigate the migration mobility. Sorption kinetics and reversibility as well as sorption mechanisms were examined. Sorption reaction occurred mostly within 10 hours on the outer surface of the sandstone particle but diffusion into the inner surface of the mineral has still occurred after that time. In order to distinguish sorption types of radionuclides, a sequential chemical extraction was introduced. The sorbed radionuclides were then extracted by applying different solutions of synthetic groundwater, CaCl$_2$, KCl and KOX-HA Especially KCl is adopted to extract the ion-exchanged cesium. Sorption types considered are reversible sorption under groundwater condition, ion exchange, association with ferro-manganese oxides or oxyhydroxides, and irreversible fixation. Strontium sorbs onto the sandstone surface mainly by fast and reversible ion exchange reaction. However, cobalt and cesium do not sorb by simple process. The main sorptive binding of cobalt was the association with ferro-manganese oxides and the secondary one was irreversible fixation. Diffusion into the lattice of minerals controlled the sorption rate of cobalt The main sorptin type of cesium was irreversible fixation, while ion exchange reaction was the secondary importance. Hence the oreder of migration mobility for the three radionuclides was Sr$^{2＋}$ ＞ Co$^{2＋}$ ＞ Cs$^{＋}$ in the sandstones.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.3
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• pp.17-24
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• 2021

Perovskite solar cells (PSCs) can be fabricated through solution process economically with variable bandgap that is controlled by composition of precursor solution. Tandem cells in which PSCs combined with silicon solar cells have potential to reach high power conversion efficiency over 30%, however, lack of long-term stability of PSCs is an obstacle to commercialization. Degradation of PSCs is mainly attributed to the mass transport of halide and metal electrode materials. In order to ensure the long-term stability, the mass transport should be inhibited. In this study, we confirmed degradation behaviors due to the mass transport in PSCs and designed buffer layers with LiF and/or SnO₂ to improve the long-term stability by suppressing the mass transport. Under high-temperature storage test at 85℃, PSCs without the buffer layers were degraded by forming PbI₂, AgI, and the delta phase of the perovskite material, while PSCs with the buffer layers showed improved stability with keeping the original phase of the perovskite. When the LiF buffer and encapsulation were applied to PSCs, superior long-term stability on 85℃-85% RH dump heat test was achieved; efficiency drop was not observed after 200 h. It was also confirmed that 90.6% of the initial efficiency was maintained after 200 hours of maximum power tracking test under AM 1.5G-1SUN illumination. Here, we have demonstrated that the buffer layer is essential to achieve long-term stability of PSCs.