• Corrosion Science and Technology
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• v.20 no.4
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• pp.175-182
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• 2021

Magnesium alloy is limited in the industrial field because its standard electrode potential is -2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 ℃. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 ℃ in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.

• 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 Korean Physical Therapy Science
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• v.9 no.2
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• pp.151-157
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• 2002

This study examined the changes in body temperature through conductive heat applied to the body and clarified the influences of body fluid on the thermal effects. Body fluid was measured using the Segmental Bioelectrical Impedance Analysis method. The subjects consisted of 13 men and 14 women. TBW was 37.56 (4.35 L for men and 29.93 (3.12 L for women, with the former being significantly (p<0.01) higher. The amount of body fluid in the right and left legs was 6.46 (0.83 L and 6.39 (0.86 L for men and 4.78 (0.49 L and 4.78 (0.49 L for women, respectively, with men's values being significantly (p<0.01) higher than women's on both the right and left sides. The maximal change in the surface temperature was 33.93 (0.61(C at the start of a warm bath to 3407 (0.61(C after 14 min for men. In contrast, the maximal change was 33.38 (0.99(C at the start to 33.73 (0.86(C after 18 min for women. For the other sites, the maximal temperature in Depths 1 and 2 was attained earlier for men than for women. The decrease in body temperature after the end of warming was more remarkable for men. Men had fluid with a higher conductivity than women, indicating influences of body fluid on the changes in body temperature. There were few changes in body composition with a partial bath having a crossed effect, indicating that this is a safe therapeutic method for elderly people.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.126-131
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• 2005

To increase the efficiency of an applicator during microwave hyperthermia therapy, first, the length from the antenna end to a slot is varied to get the optimal matching of the characteristic impedance at the frequency of 2.45 GHz. Using the electric and thermal constants of biological tissue, we compose a phantom to calculate temperature increment as well as the resonance characteristics and the SAR distributions. The proposed 3-slot sleeve antenna inserted in an applicator plays an effective role in increasing the therapy size in the view of heating performance as electromagnetic energy tends to concentrate on not feed point direction but treatment area. The SAR is then used in combination with a finite difference heat transfer equation to determine the temperature distribution. Also, in order to shorten treatment time and increase therapy size, a square-array structure is suggested and analyzed.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.243.2-243.2
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• 2015

We report a high-performing nanoscale NiO thin film grown by thermal oxidation of sputtered Ni film. The structural, physical, optical and electrical properties of nanoscale NiO were comprehensively investigated. A quality transparent heterojunction (NiO/ZnO) was formed by large-area applicable sputtering deposition method that has an extremely low saturation current of 0.1 nA. Considerable large rectification ratio of more than 1000 was obtained for transparent heterojunction device. Mott-Schottky analyses were applied to develop the interface of NiO and ZnO by establishing energy diagrams. Nanoscale NiO has the accepter carrier concentration of the order of 1018 cm-3. Nanoscale NiO Schottky junction device properties were comprehensively studied using room temperature impedance spectroscopy.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.56-59
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• 2003

As electric power systems grow to supply the increasing electric power demand short-circuit current tends to increase and impose a severe burden on circuit breakers and power system apparatuses. Thus, all electric equipment in a power system has to he designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Among current limiting devices, Fault Current Limiter (FCL) is expected to reduce the short-circuit current. Especially, Superconducting Fault Current Limiters (SFCL) offer ideal performance: in normal operation the SFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. The SFCL using high-temperature superconductors offers a positive resolution to controlling fault-current levels on utility distribution and transmission networks. This study contributes to the EMTDC based modeling and simulation method of DC Reactor type SFCL. Single and three phase faults in the utility system with DC reactor type SFCLs have been simulated using EMTDC in order to coordinate with other equipments, and the results are discussed in detail.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.410-411
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• 2009

The multi-component ceramic proton conductor, $BaZr(Y)O_3-SiO_2-TiO_2-ZrO_2$ (BZY-STZ) and $LaPO_4-SiO_2-TiO_2-ZrO_2$ (LP-STZ), were synthesized by micro-emersion and sol-gel technique. The characterization of proton conductors were carried out using X-ray diffraction(XRD), thermogravimetric analysis(TGA), differential thermal analysis(DTA), impedance analysis. The proton conductors indicate the possibility of application for the intermediate temperature up to $700^{\circ}C$.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.349-352
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• 1997

The EEG amplifier satisfies high gain, high common mode rejection ratio(CMRR), high input impedance, low thermal drift, low noise and good d.c. performance. The Bipolar amplifier of this paper safisfies above categories and aim at minimization of the ESU(electric surgical unit) interference.

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.189-192
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• 2001

In order to prepare the proton-conducting membrane with lower cost and higher ionic conductivity than commercialized one, the concept of incorporating the nitrogen acid to polymer backbone, is proposed. The synthesis, thermal, and temperature-variable impedance/electrical conductivity studies of poly (p-tolunesulfonylamido acrylate) are reported. This polymer can be prepared by reacting poly (acryloyl chloride) with ptolunesulfonamide and cast into homogeneous membranes. Thermogravimetric analysis (TGA) shows that the polymer is thermally stable up to about $200^{\circ}C$ and Differential scanning calorimetry (DSC) illustrates that the glass transition occur at around $67^{\circ}C$. The ionic conductivity measured by dielectric spectroscopy is in the range of $10^{-5}\;S/cm$ in dry atmosphere that it can be a candidate for the membrane of PEMFC or DMFC.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.3
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• pp.341-350
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• 2012

In this paper we observe the protective coatings carbon for steel, aluminium and titanium alloys were obtained by plasma electrolytic oxidation (PEO) under unipolar and bipolar conditions. The anticorrosion properties and the thermal stability of the surface layers were studied by electrochemical impedance spectroscopy and potentiodynamic polarization. It was found that the application of the bipolar PEO mode enables one to synthesize the surface layers that possess enhanced anticorrosion and mechanical properties. results of research of antiscale PEO - coatings for marine power equipment are presented. The combined method of prevention of corrosion and scale formation was tested at the industrial plants of Russian Shipyard "Zvezda".