Determination of Hydrogen Diffusion Parameters of Ferritic Steel from Electrochemical Permeation Measurement under Tensile Loads

The hydrogen permeation experiment, performed with a stepwise permeation sequence involving "1st permeation-desorption-2nd permeation under loading, demonstrates that fine blister cracks are frequently observed on the steel surface in hydrogen charging side after the 2nd permeation under the load over 95% of yield strength of the steel. To accommodate the experimental phenomena under the loading conditions, a numerical model is developed for determination of hydrogen diffusion parameters of the sour-resistant ferritic steel evaluated under tensile stress in plastic ranges. To solve the modified diffusion equation, a numerical finite difference method (FDM) is employed. The diffusion parameters determined by curve-fitting with the newly proposed diffusion equation indicates that, with the transition of mechanical domain from local-plasticity to generalized-plasticity, a big increase in the crack formation rate and hydrogen capture rate per irreversible trap are observed. It suggests that the transition probability for hydrogen transport from interstitial lattice site to irreversible trap site increases with the stress level. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.1110Ysciescopu

Alloy Design to Prevent Intergranular Corrosion of Low-Cr Ferritic Stainless Steel with Weak Carbide Formers

Effect of weak carbide formers, Mo, Mn and Si, on intergranular corrosion (IGC) of low-Cr ferritic stainless steel is analyzed after IGC test using TEM and three dimensional atom probe. The co-addition ofMo, Mn and Si to low-Cr ferritic stainless steel effectively prevents IGC by forming along grain boundaries CMn4MoSi intermetallic compounds, which act not only as carbon trap sites but also as diffusion barrier against solute Cr diffusion toward grain boundaries. The low solubility of Cr in the CMn4MoSi intermetallic compound results in replenishing Cr in the Cr-depleted area. (C) The Author(s) 2015. Published by ECS. All rights reserved.114Ysciescopu

Double phase anisotropic variational problems involving critical growth

In this paper, we investigate some existence results for double phase anisotropic variational problems involving critical growth. We first establish a Lions type concentration-compactness principle and its variant at infinity for the solution space, which are our independent interests. By employing these results, we obtain a nontrivial nonnegative solution to problems of generalized concave-convex type. We also obtain infinitely many solutions when the nonlinear term is symmetric. Our results are new even for the $p(\cdot)$-Laplace equations

Reduction in CO2 uptake rates of red tide dinoflagellates due to mixotrophy

We investigated a possible reduction in CO2 uptake rate by phototrophic red tide dinoflagellates arising from mixotrophy. We measured the daily ingestion rates of Prorocentrum minimum by Prorocentrum micans over 5 days in 10 L experimentalbottles, and the uptake rates of total dissolved inorganic carbon (CT) by a mixture of P. micans and P. minimum(mixotrophic growth), and for the predator P. micans (phototrophic growth; control) and prey P. minimum (phototrophicgrowth; control) alone. To account for the effect of pH on the phototrophic growth rates of P. micans and P. minimum,measurements of CT and pH in the predator and prey control bottles were continued until the pH reached the same level(pH 9.5) as that in the experimental bottles on the final day of incubation. The measured total CT uptake rate by the mixtureof P. micans and P. minimum changed from 123 to 161 μmol CT kg-1 d-1 over the course of the experiment, and waslower than the CT uptake rates shown by P. micans and P. minimum in the predator and prey control bottles, respectively,which changed from 132 to 176 μmol CT kg-1 d-1 over the course of the experiment. The reduction in total CT uptake ratearising from the mixotrophy of P. micans was 7-31% of the daily CT uptake rate seen during photosynthesis. The resultssuggest that red tide dinoflagellates take up less CT during mixotrophy.1131Ysciescopuskc

Geometrical Acoustics in a Heterogeneous Anisotropic Elastic Solid: Application to a Wavy Composite

Karal and Keller [1] developed the geometrical acoustics for wave propagation in a heterogeneous isotropic medium, generally adopting the methods used in geometrical optics [2,3]. It is very difficult to find a solution for wave propagation in a heterogeneous anisotropic medium. Here, instead of finding an exact solution, we extend the geometrical acoustics to a heterogeneous anisotropic medium to untangle the behavior of wave fronts spreading into an undisturbed region. The eikonal equation which contains information of the phase and group velocities, along with the transport equation which governs the amplitude of propagating waves, are derived. For a one-dimensionally heterogeneous anisotropic solid, wave propagation is two dimensional and it is possible to obtain closed-form analytic formulas for the ray path and travel time of a ray. These formulas are applied to find the path and travel time of rays generated from a pointlike source and detected by a small detector. The predicted arrival times agree well with observed values