• Journal of the Korea Institute of Building Construction
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• v.9 no.3
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• pp.109-116
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• 2009

The magnesium sulfate solution digestion test carried out for resistance of concrete containing waste glass powder on magnesium sulfate attack. Moreover, it yielded S.D.F index was used for the criteria of quantitative assessment to the resistance of magnesium sulfate for the purpose of evaluation of chemical deterioration on concrete. Furthermore, to evaluate for micro-cracks within concrete and external corrosion, the weight variation of specimens and the dynamic elasticity were compared and analyzed and also the applicability was examined using the analysis of product of hydration through out observing external deformation and micro-structural deformation.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.214-216
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• 1995

Passive films formed on chromium surface in citrate buffer solution were investigated by means of three-parameter ellipsometry. The citrate buffer was found to be a suitable medium in which oxide film on chromium could be removed by cathodic treatment, providing a reference surface for the optical study. The passive film effectively protecting the chromium surface from corrosion was found to have thicknesses in the range 0.65 to 1.25 nm depending on the potential in the range of -0.20 to 0.60 V (0.1M KCl calomel electrode). The complex refractive index of the passive film did not show significant potential-dependent changes, indicating that the composition of the film material does not depend on potential.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.61-68
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• 2016

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E91T1-B9C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, tempered martensite and lower bainite were formed in first layer of weld metal. The amount of tempered martensite was decreased and the amount of lower bainite was increased with increasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered Martensite and lower Bainite. Tensile strengths of dissimilar welds decreased with increasing heat inputs. Dissimilar welds seemed to have a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals showed that the corrosion rate increased with increasing heat inputs due to the increase of the amount of lower Bainite.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.37-45
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• 2000

The underground buried pipelines of Natural gas are relatively safer than any other pipelines of chemical plants, because Natural gas is non-corrosive fluid. But Natural gas is supplied normally the downtown area. So, it may be a disaster because of corrosion which is caused interference facilities, environment and third party accident which is caused facilities construction. Especially, it is very difficult to find out and inspect damages of pipeline because of buried pipelines. Therefore this paper approached to select and manage risk region pipelines according to introduction of underground buried pipeline's risk concept. Risk was indicated three parts - corrosion factor, design and construction factor, maintence and management factor - in this paper, Therefore qualitive risk of pipelines showed score as quantitative number. Also it was thought to be helpful in confidence and safety management that the concept of key index and failure supplementation measures to cost introduces this program. We developed this risk assessment program using visual basic tool and interfaced GIS.

• Journal of Surface Science and Engineering
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• v.45 no.6
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• pp.219-225
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• 2012

The aim of the present study was to investigate the corrosion resistance and characteristics of passive layer between naturally passivated and chemically passivated duplex stainless steel, UNS S31803 (EN 1.4462) using CPT, XPS, and EIS. The treatment of $HNO_3$(II) and $HNO_3$(III) in ASTM A 967 was applied. In case of chemically passivated specimen, CPT of $HNO_3$(II) and $HNO_3$(III) were higher than that of naturally passivated specimen. In addition, from XPS results, the protectiveness index (Cr/(Fe+Cr)) of chemically passivated specimens was also higher than that of naturally passivated specimen. The reason for this result is considered due to post-cleaning treatment in chemical passivation process, that is, immersion in $Na_2Cr_3O_7$ solution. The fact that $HNO_3$(II) passivation treatment showed the highest film resistance and 'n', which is exponent related with constant phase element (CPE) of passivation film, was in good agreement with results of CPS and XPS. The chemical passivation treatment was an effective method to improve corrosion resistance of duplex stainless steel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.111-118
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• 2010

Reinforced steel corrosion due to concrete carbonation is one of main factors on the durability of RC structure. The carbonation velocity have an effect on carbon dioxide density, concrete quality and structural shape. Specially, these problems have increased in urban area. This study investigates the carbonation status of the bridges and quantifies the effect of carbonation based on various domestic field data. The failure probability of durability is evaluated on the basis of reliability concept. According to experimental results of the carbonation depth, the carbonation depth increased with structural age and carbonation velocity decreased with high strength of concrete. In most cases, the failure probability of durability by carbonation was more than 10%. Also, The results requires the minimum cover thickness of 70-80mm for target safety index(${\beta}$=1.3) proposed by Korean concrete specification.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.697-703
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• 2023

In this study, a modified indirect evaluation method was developed to predict the deterioration level of water pipes. The accuracy of the modified method was verified by comparing it with the direct method. The weights of index were adjusted by reducing the weight of water quality corrosion, soil corrosion, lay depth and road type according to the importance of the existing evaluation factors and adding the weight of pipe thickness. In the results, the weight of pipe thickness was determined to be 0.1530. Comparing with the direct evaluation method, the accuracy of the modified indirect evaluation method increased by 31.03% compared to the indirect evaluation method. The modified indirect evaluation method will be able to select relatively old pipes more accurately and efficiently than the existing indirect evaluation method when prioritizing the improvement of old water pipes.

• Journal of Korea Water Resources Association
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• v.57 no.8
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• pp.561-569
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• 2024

In this study, a damage estimation model for water distribution system was developed to quantitatively calculate the cumulative damage of water distribution system. And it was applied to real water distribution system to analyze the cumulative damage of water distribution system. To analyze the overall damage rate of the water distribution system, the cumulative damage analysis formula of individual pipes was established. And the aging index that affects the damage rate was analyzed using MCS (Monte Carlo Simulation), and Romanoff's measured data was used to calculate the thickness change due to corrosion. In addition, a cumulative damage estimation model was applied to unit network such as small and medium block network, and the cumulative damage of the unit network for up to 50 years was calculated. From the results, it was found that the cumulative damage rate is increased from 7% to 79% for the water distribution system of Naeduk 1-dong, Cheongju City, as the age of the pipeline is increased from 20 years to 50 years.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.260-266
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• 2009

Non-revenue water reduction(NRW) technologies are implemented to evaluate and manage leakages scientifically in water distribution systems under local governments. A development of quantitative leakage indicator by measuring minimum night flow, pressure control policy by installation of PRV(pressure reducing valve) and the establishment of leakage prevention schemes by residual life modeling of deteriorated water pipes are reviewed and studied. Estimation models of allowable leakage are developed by measuring and analyzing minimum night flow at residential and commercial area in Nonsan city, which is suggested from UK water industry and can improve an existing leakage indicator for the evaluation of non-revenue water. Also, pressure control method is applied and analyzed to Uti distribution area in Sacheon city in the operation aspect. As results, $466\;m^3/day$ of leakage can be reduced and it is expected that 113million won of annual cost can be saved. In the part of corrosion velocity and residual life assessment, non-linear prediction models of residual thickness are proposed by assessment of corrosion velocity based on exposure years, soil and water quality etc., since the deteriorated water pipe play a major role to increase leakage. It is expected that collection data and analyzing results can be applied effectively and positively to reduce non-revenue water by accumulating surveying data and verifying the results in the business field of water distribution systems under local governments.