• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.308-315
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• 2013

In this paper, Tapered slot antenna of IR-UWB was Designed and fabricated using HFSS and we suggest the beam width of the broadband antenna using group-delay and fidelity. For this purpose, acquired data from the Network Analyzer was analyzed in the time domain by using the chirp-Z transform and Simulation was conducted and confirmed with the CST microwave studio. Analysis of the antenna radiation pattern is the antenna separation at intervals of 0.5 metres and then transmit antenna is fixed and the receiving antenna 360 degree intervals of 10 degree each, The results of the analysis are as follows, and analyzer of the fidelity of the antenna's performance. An analysis of more than 90 percent of the cases is less than ${\pm}40$ degrees in good fidelity, more than 90% less than ${\pm}40$ degrees and lowe fidelity. In conclusion, Analysis of Beam width of wideband antenna with more precise is possible through using these radiation pattern using fidelity.

• Corrosion Science and Technology
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• v.11 no.2
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• pp.56-64
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• 2012

Factors affecting corrosion of stainless steels such as pH, oxidation and redox potential (ORP), soil resistivity, water content of soil, chloride ion concentration, bacteria activity, and corrosion potential have been investigated using soil analysis, bacterial analysis, surfacial analysis, and analysis of corrosion potentials of several stainless steels buried in 8 sites of Seoul metropolitan for one year. Corrosion potential was affected by occurrance of corrosion as well as bacteria activity but the behavior of corrosion potential with time is different depending on occurrance of corrosion and bacteria activity. The main factor affecting corrosion of stainless steels in soil is level of chloride ion concentration which is also a main factor affecting corrosion of stainless steels in chloride containing drinkable water. Furthermore, guideline of stainless steels in drinkable water is concluded to be applicable to that in soil by the results from surfacial analysis.

• Composites Research
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• v.27 no.5
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• pp.190-195
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• 2014

This paper predicts the complex permittivity of MWNT added epoxy depending on agglomeration by numerical analysis. 1wt% MWNT added epoxy specimen is prepared using 3-roll-mill method and its complex permittivity is measured in X-band (8.2~12.4 GHz) using freespace measurement system. The analytic model is comprised of cube epoxy and perfect sphere agglomeration. The complex permittivity of the agglomeration model is predicted by complex permittivity mixing rule using the measured complex permittivity of epoxy and 1 wt% MWNT added epoxy. Commercial electromagnetic analysis software, CST, is used to obtain S-parameter of the analytic model and MATLAB code is used to calculate complex permittivity from the S-parameter. It is confirmed that the complex permittivity increases when the agglomeration size decreases.

• Corrosion Science and Technology
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• v.16 no.6
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• pp.294-297
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• 2017

For the longer service life of steel pile, cathodic protection is selected sometimes at corrosive environment. The cathodic protection design improvement was investigated in this study. The current demand for cathodic protection was calculated from the potentiostatic current monitoring of the steel specimen in the deaerated soil samples. In this study, the current distribution was studied using the Boundary Element Method (BEM) and the Finite Element Method (FEM) numerical analysis methods. The optimum layout of the anode was developed and confirmed by numerical analysis. Under the conventional design of the anode, the length of the anode hole is same as the pile length. We found that, at the bottom end of the pile, the current density is too high. When the anode hole length was 80% of the pile length, the current consumption at the end was reduced. The construction cost of anode hole drilling was decreased about 20%, as compared to the conventional design. Furthermore, the life of the anode materials could be extended by reducing the current consumption at the end section. Using this approach, the construction cost was reduced significantly without any under-protection area on the steel piles.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.115-121
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• 2020

In this study, erosion tests and erosion-corrosion tests of Al5083-H321 aluminum alloy were conducted at various flow rates in seawater. The erosion tests were conducted at a flow rate of 0 to 20 m/s, and erosion-corrosion tests were performed by potentiodynamic polarization method at the same flow rate. Characteristic evaluation after the erosion test was conducted by surface analysis. Characteristic evaluation after the erosion-corrosion test was performed by Tafel extrapolation and surface analysis. The results of the surface analysis after the erosion test showed that surface damage tended to increase as the flow rate increased. In particular, intermetallic particles were separated due to the breakdown of the oxide film at 10 m/s or more. In the erosion-corrosion test, the corrosion current density increased as the flow rate increased. Additionally, the surface analysis showed that surface damage occurred in a vortex shape and the width of the surface damage tended to increase as the flow rate increased. Moreover, damage at 0 m/s, proceeded in a depth direction due to the growth of pitting corrosion, and the damaged area tended to increase due to acceleration of the intermetallic particle loss by the fluid impact.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.113-120
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• 2024

An attempt was made to apply digital image correlation (DIC) strain analysis to in-situ scanning electron microscopy (SEM) observations of bending deformation to quantify local strain distribution inside a ZnMgAl-alloy coating in deformation. Interstitial-free steel sheets were hot-dipped in a Zn-3Mg-6Al (mass%) alloy melt at 400 ℃ for 2 s. The specimens were deformed using a miniature-sized 4-point bending test machine inside the SEM chamber. The observed in situ SEM images were used for DIC strain analysis. The hot-dip ZnMgAl-alloy coating exhibited a solidification microstructure composed of a three-phase eutectic of fine Al (fcc), Zn (hcp), and Zn2Mg phases surrounding the primary solidified Al phases. The relatively coarsened Zn₂Mg phases were locally observed inside the ZnMgAl-alloy coating. The DIC strain analysis revealed that the strain was localized in the primary solidified Al phases and fine eutectic microstructure around the Zn₂Mg phase. The results indicated high deformability of the multi-phase microstructure of the ZnMgAl-alloy coating.

• Korean Journal of Culture and Social Issue
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• v.19 no.4
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• pp.553-576
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• 2013

The purpose of this study was to investigate the impact of retirement stress, character strengths and marital dissatisfaction on depression. Additionally this study examined direct effects and indirect effects of character strengths and marital dissatisfaction. The participant group was composed of 197 retired men living in Daegu and Gyongsangbuk-do. The Retirement Stress Scale (RSS), Character Strengths Test (CST), Korean Marital Satisfaction Inventory (K-MSI), and Center for Epistemology Studies Depression scale (CES-D) were administered to participants. Structural Equation Modeling (SEM) with AMOS was used for the purpose of analysis. The results of the study were as follows. First, an increase in retirement stress was associated with higher levels of depression. Second, hierarchical regression analysis indicated that higher levels of optimism significantly predicted higher depression. Also hierarchical regression analysis indicated that lower levels of appreciation of beauty and excellence without optimism significantly predicted higher depression. Furthermore, increases in marital dissatisfaction were associated with higher levels of depression. Third, the constructed model including both direct effects and indirect effects appeared to fit better than alternative model in explaining relationships between retirement stress and depression. In other words, character strengths and marital dissatisfaction appeared to affect the depression levels of retired men directly and indirectly. To sum up, this study demonstrated that the factors which had an effect on depression in retired men, character strengths and harmonious marital relationships appeared to act as a buffer against depression in retired men. The current results might serve as basic data for psychological well-being programs for retired men. Finally, the limitations and implications of the current study were discussed.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.135-140
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• 2016

Piping and equipment are degraded by flow-accelerated corrosion (FAC) in nuclear power plants. FAC causes numerous problems and nuclear utilities maintain programs to control FAC. The key parameters influencing FAC are hydrodynamic conditions, water chemistry, and effect of materials. Recently, a nuclear utility has planned slight power uprates in Korea. Operating conditions need to be changed in the secondary system according to power uprates. This study analyzed the effect of wall-thinning caused by power uprates. The change of operation data in the secondary cycle is reviewed, and wall-thinning rates are analyzed in the main lines. As a result, two phase (mixture of water and steam) lines have a greater impact than a water line under power uprate conditions. Also, the quality of steam is the most important factor for FAC in two phase lines.

• Corrosion Science and Technology
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• v.10 no.3
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• pp.95-100
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• 2011

Protective coatings play an important role in the protection of metallic structures against corrosive environment. The main function of anticorrosive coating is to prevent the materials from corrosive agents, such as water, oxygen and ions. In the study, the corrosion protection properties of urethane and epoxy coating systems were evaluated using EIS methods exposed to the corrosion acceleration test such as Norsok M501, Prohesion and hygrothermal cyclic test. AFM analysis of the coating systems was carried out to monitor the change of roughness of coatings. Urethane coating system was more stable than the epoxy coating under given cyclic conditions. Water uptake into the urethane coatings was less than that into the epoxy coating. The urethane coating system showed better corrosion protection than epoxy coating system based on the changes of the impedance modulus at low frequency region with exposure time. Consequently, the corrosion protection properties of the epoxy and urethane coatings was well correspond with their surface roughness changes and water uptakes.

• Corrosion Science and Technology
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• v.13 no.4
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• pp.125-129
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• 2014

Shinning spot defects on galvanized steel sheets were studied by optical microscope, scanning electron microscope(SEM), Energy Dispersive Spectrometer (EDS) and Laser-Induced Breakdown Spectroscopy Original Position Statistic Distribution Analysis (LIBSOPA) in this study. The research shows that the coating thickness of shinning spot defects which caused by the substrate defect is much lower than normal area, and when skin passed, the shinning spot defect area can not touch with skin pass roll which result in the surface of shinning spot is flat while normal area is rough. The different coating morphologies have different effects on the reflection of light, which cause the shinning spot defects more brighter than normal area.