• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.175-177
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• 2006

Here we report an enhanced flexoelectric switching in a self-assembled system of smectic liquid crystal and some specific dopant. The assembled unit block seemed to have electric dipole and as a result induces large flexoelectric polarization due to its asymmetric shape and shows fast switching to the electric field. The unit blocks are oriented in a helical fashion in the cell with large gap (${\sim}5{\mu}m$) and shows selective reflection property. In the thin cell (${\sim}2{\mu}m$), the unit blocks are aligned homeotropically on the bare ITO substrate with no surface treatment and shows fast decaying time.

• 연구논문집
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• s.31
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• pp.157-163
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• 2001

Evolution of microstructure due to service exposure to high temperature has a strong effect performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of $Fe_2Mo$-type laves phases and coarcening of $M_23C_6$-type carbides is the primary cause of degradation of mechanical properties such as creep resistance, tensile strength and toughness. Creep tests have been carried out on pre-aging mod. 9Cr-1Mo steels to examine the effect of pre-aging and stress on the creep strength. Based on the results, a nondestructive procedure, where electrochemical technique that quantitatively detect laves phases and $M_23C_6$-type carbides in a material is used, has been proposed to evaluate a residual creep life of mod. 9Cr-1Mo steels.

• Corrosion Science and Technology
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• v.17 no.3
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• pp.101-108
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• 2018

AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with $10{\mu}m$ thick $Al_2O_3$ ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.81-87
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• 2009

An indium-tin oxide (ITO) coated spinel manganese oxide (${LiMn_2}{O_4}$, LMO) is prepared and its high-temperature ($55^{\circ}C$) cycle performance and rate capability are examined. A severe electrolyte decomposition and film deposition is observed on the un-coated ${LiMn_2}{O_4}$ cathode, which leads to a significant electrode polarization and capacity fading. Such an electrode polarization is, however, greatly reduced for the ITO-coated (> 2 mol%) LMO cathode, which leads to an improved cycle performance. This can be rationalized by a suppression of electrolyte decomposition, which is in turn indebted to a decrease in the direct contact area between LMO and electrolyte. The suppression of film deposition on the ITO-coated LMO cathode is confirmed by infra-red spectroscopy. The rate capability is also improved by the surface coating, which may be resulted from a suppression of resistive film deposition and high electric conductivity of ITO itself.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.3
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• pp.239-245
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• 1983

Electrochemical adsorption always was accompanied with solvent displacement and relative size factor(x) of adsorbate and solvent and hydrogen coverage(${\theta}$) on the lead anodic film electrode formed in phosphoric acid in NaCl solution and the sea water at $15{\sim}35^{\circ}C$ were studied by means of constant current-potential method and potentiodynamic cathodic polarization method. In this experiment, various constants and thermodynamic quantities calculated from the hydrogen coverage were also described to explain the reactivities of di-iso-butylnitrosoamine(DBNA) and proton ($H^+$) according to the changes of interactions between solute and solvent in the bulk phase and interphase. It was investigated that the average values of relative size factor and the coverage of hydrogen atoms studied with the electrode of lead anodic film formed in phosphoric acid solution in 60mM DBNA+0.5M NaCl and in 60mM DBNA+$6\%0$ sea water were about 11.0 and 0.2 respectively. Hydrogen evolution was electrochemical mechanism because of substitutional adsorption of aromatic substance with their delocalization of electrons, but in the case of non-charge transfer adsorption of aliphatic substance(DBNA) interacting relatively little with the electrode, it was combination mechanism.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.3
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• pp.177-184
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• 1999

The charge-discharge characteristics of the $Mg_2Ni-x$ wt.%Nd (x = 0~3) electrodes were investigated. The electrodes were prepared by the mechanical grinding of the induction-melted $Mg_2Ni$ alloy powders with Ni and/or Nd using planetary ball mill apparatus. The discharge capacity of the $Mg_2Ni$ alloy increased with the increase in the nickel content. The electrode possessing 100 wt.% nickel powder showed the initial capacity of 760 mAh/g and the capacity decay with the cycle number was less than that of the 55 wt.% nickel powder. The Nd was added to this composition. It was found that the $Mg_2Ni-100$ wt.%Ni -0.2 wt.%Nd alloy showed an excellent charge-discharge cycle characteristics compared with the other reported Mg-Ni alloy system. The discharge capacity was 400 mAh/g after 70 cycles. Such an improved cycle life seems to be attributed to the improvement in the corrosion characteristics of the alloy. The anodic polarization curve of the $Mg_2Ni-100$ wt.%Ni-0.2 wt.%Nd alloy exhibited better passivating behavior than that of the $Mg_2Ni-100$ wt.%Ni.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.6
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• pp.19-30
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• 2013

This study is to evaluate the use of dual-polarization radar data for storm runoff modeling in Namgang dam (2,293 $km^2$) watershed using KIMSTORM (Grid-based KIneMatic wave STOrm Runoff Model). The Bisl dual-polarization radar data for 3 typhoons (Khanun, Bolaven, Sanba) and 1 heavy rain event in 2012 were obtained from Han River Flood Control Office. Even the radar data were overall less than the ground data in areal average, the spatio-temporal pattern between the two data was good showing the coefficient of determination ($R^2$) and bias with 0.97 and 0.84 respectively. For the case of heavy rain, the radar data caught the rain passing through the ground stations. The KIMSTORM was set to $500{\times}500$ m resolution and a total of 21,372 cells (156 rows${\times}$137 columns) for the watershed. Using 28 ground rainfall data, the model was calibrated using discharge data at 5 stations with $R^2$, Nash and Sutcliffe Model Efficiency (ME) and Volume Conservation Index (VCI) with 0.85, 0.78 and 1.09 respectively. The calibration results by radar rainfall showed $R^2$, ME and VCI were 0.85, 0.79, and 1.04 respectively. The VCI by radar data was enhanced by 5 %.

• Transactions on Electrical and Electronic Materials
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• v.7 no.2
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• pp.72-75
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• 2006

Ferroelectric PZT heterolayered thick films were fabricated by the alkoxide-based sol-gel method. PZT(Zr/Ti=60/40) paste was made and alternately screen-printed on the $Al_2O_3$ substrates. We have introduced a press-treatment to obtain a good densification of screen printed films. The porosity of the thick films was decreased with increasing the applied pressure and the thick films pressed at $0.6ton/cm^2$ showed the dense microstructure and thickness of about $76{\mu}m$. The relative dielectric constant increased with increasing the applied pressure. The remanent polarization and coercive field increased with increasing applied pressure and the values for the PZT thick films pressed at $0.6ton/cm^2$ were $16.6{\mu}C/cm^2$, 76.9 kV/cm, respectively.

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.45-51
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• 2001

고체산화물 연료전지의 삼상 계면의 길이를 증가시키기 위해 Glycine-Nitrate Process(GNP)를 이용하여 환원극 재료인 L $a_{0.5}$S $r_{0.5}$Mn $O_3$(LSM)과 전해질 재료인 C $e_{0.8}$G $d_{0.2}$ $O_{1.9}$(CGO)를 합성하였다. 적당한 합성조건을 찾기 위하여 글리신의 양을 달리하여 분말을 합성한 결과 LSM의 경우 글리신이 양이온 몰수의 2배일 때 perovskite상이 얻어졌으며 비표면적은 34$m^2$/g 이었다. 합성된 LSM과 CGO 분말을 50:50 wt%로 혼합하여 제작된 환원극을 screen-printing법으로 코팅한 후 각각 1200, 1300, 1350 및 140$0^{\circ}C$에서 4시간 동안 소결한 후 80$0^{\circ}C$에서 power density와 양극과전압 등을 측정한 결과 130$0^{\circ}C$에서 소결한 단위전지에서 최대 309 mW/$ extrm{cm}^2$의 power density를 얻을 수 있었다.다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.83-90
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• 2017

The corrosion behavior of a rebar in concrete according to the amount of NaCl and $LiNO_2$ was observed by using Electrochemical Impedance Spectroscopy. The corrosion was accelerated in a short time by using dry/wet cycles method, which is one of the corrosion acceleration methods, and though the value of measured impedance, equivalent circuit can be introduced. It was confirmed that the passive film of a embedded rebar in concrete with NaCl was broken quickly, and when $0.6M\;LiNO_2$ was added, the velocity of ongoing corrosion was declined considerably compared to the amount of NaCl. However, when $1.2M\;LiNO_2$ was added, it was confirmed that the passive film was not broken and its performance remained, compared to the amount of NaCl.