Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
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Volume 61, Issue 7
Displaying 1-4 of 4 articles from this issue
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Commentary
Review
  • Life Cycle Management of Port Structures - VII
    Kazuaki Zen
    2012 Volume 61 Issue 7 Pages 263-268
    Published: July 15, 2012
    Released on J-STAGE: December 29, 2012
    DOIhttps://doi.org/10.3323/jcorr.61.263
    JOURNAL FREE ACCESS
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    In the port of Kamsar, the PW method has been used for assessing the repair methods of the structure. The assessment requires cashflow data, which should normally include costs and incomes. If all the costs and incomes in a cashflow are discounted to their PW values using the chosen discount rate (r) and then summed, the result is the PW value of the cashflow. And there are some variations of the PW equation corresponding to the costs and incomes in a cashflow.
    In accordance with the relationships between discount factors and time for different rates, it is supposed that the future is too uncertain to justify costing beyond 30 years. In practice, the lives of concrete bridges have to be significantly longer. For this problem, a tapering discount rate has been proposed which may be 8% up to 20 years but thereafter it tapers linearly down to 3%.
    In this paper, the variations of the PW equation, the terms on the PW, and the application of a tapering discount rate to the port structure in Kamsar are shown.
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Research Paper
  • Dissolution of Dy2O3 and Nd2O3 by Electrolysis of Fused Na2SO4 and the Recovery of Dy and Nd
    Michihisa Fukumoto, Masayuki Odera, Kenji Yokoyama, Motoi Hara
    2012 Volume 61 Issue 7 Pages 278-282
    Published: July 15, 2012
    Released on J-STAGE: December 29, 2012
    DOIhttps://doi.org/10.3323/jcorr.61.278
    JOURNAL FREE ACCESS
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    The dissolution behavior of Dy2O3 and Nd2O3 powders under the control of the O2− activity of fused Na2SO4 by electrochemical polarization of platinum electrode was investigated. The solubility of Dy2O3 and Nd2O3 in fused Na2SO4 increased in the anodic potential region, while their solubility did not increase in the cathodic potential region. The both oxides were subject to acid dissolution. The cathodic current density in the molten salt after the acid dissolution of both the oxides was higher than that in the molten salt without the oxide dissolution. Therefore, it was found that the cathodic reduction reaction of dissolving metal ion occurred. It was observed that Dy and Nd were deposited on electrode surface by potentiostatically cathodic polarization using the molten salt after the oxide dissolution experiment.
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  • Numerical Simulations for Time-dependent Corrosion Surfaces of Unpainted Carbon Steel Plates in Atmospheric Corrosive Environments Using Spatial Statistical Techniques
    Shigenobu Kainuma, Young Soo Jeong, Kazuhiro Utsunomiya, Jin Hee Ahn
    2012 Volume 61 Issue 7 Pages 283-290
    Published: July 15, 2012
    Released on J-STAGE: December 29, 2012
    DOIhttps://doi.org/10.3323/jcorr.61.283
    JOURNAL FREE ACCESS
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    Many severe corrosion damages have been reported in steel structures constructed in a period of high economic growth. To ensure the safety of such structures, it is important to devise a method how corrosion develops in the service. However, method of predicting such behavior has not yet been established. In this research, semi-variogram analyses were carried out on time-dependent corrosion surfaces of unpainted steel plates exposed to atmospheric environment to clarify the spatial autocorrelation structures and their time-dependence. In addition to this, by using the autocorrelation structures and an ordinary kriging technique, method of spatial statistical simulation for the time-dependent corrosion surfaces in various atmospheric corrosive environments was proposed. Moreover, example of the relationship between mean and maximum corrosion depths was proposed on the basis of simulated results of time-dependent corrosion surfaces of unpainted carbon steel plates.
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