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Iwashita T.,Ariake National College of Technology | Azuma K.,Sojo University
Journal of Structural Engineering (United States) | Year: 2012

Over the past two decades, plastic constraint effects have been an issue of concern in both fracture mechanics and structural integrity research, and several methods have been proposed for considering loss of plastic constraint. This paper shows the ability of a simplified model to predict brittle fracture under low plastic constraint conditions. Fracture toughness tests are performed on single-edge notched bend (SENB) steel specimens with deep and shallow notches, as well as on double-edge notched tension and center-notched tension (CNT) specimens. When compared with SENB specimens with a deep notch, the CNT specimens show high fracture toughness as a result of the loss of plastic constraint at the crack tip. Here, the Weibull stress approach and a toughness scaling model (TSM) are used to consider the effects of the loss of plastic constraint on the fracture toughness of the specimens. The corrected fracture toughness values evaluated by the TSM are found to be close to the toughness values observed in the tests and to the values predicted by the Weibull stress approach. This paper also briefly discusses the effect of ductile crack growth on brittle fracture. © 2012 American Society of Civil Engineers. Source


Yamamoto M.,Tokyo University of Science | Liu D.,Ariake National College of Technology
Journal of Material Cycles and Waste Management | Year: 2013

Coastal areas in Japan and other parts of the world have serious problems with barren grounds. A method has been developed that uses a mixture of steelmaking slag and compost including humic substances supplied in seawater, for restoring seaweed beds. The effects of this method have been previously confirmed in field tests. It was found that the mixture of steelmaking slag and compost was effective for extending the lifetime of iron elution as well as increasing iron concentrations in seawater. In this study, the effect of the mixing composts with steelmaking slag was evaluated additionally for increasing dissolved iron concentrations in seawater. The characteristics of iron elution were also studied using this method. In particular, the mechanism of Fe elution and dissolved Fe oxidation was examined in detail. The iron elution of actual seawaters was tested using three kinds of samples which involved steelmaking slag, compost, and a mixture of steelmaking slag and compost. These samples were used to understand the mechanism of Fe elution and oxidation in seawater. It was found that the mixture of steelmaking slag and compost was the most effective, which also confirmed the validity of the proposed Fe elution process in seawater. © 2013 Springer Japan. Source


Nishimura T.,University of Kitakyushu | Sanada Y.,University of Kitakyushu | Matsuo T.,University of Kitakyushu | Okobira T.,Ariake National College of Technology | And 3 more authors.
Chemical Communications | Year: 2013

An amphiphilic macrocycle based on pillar[5]arene with polar lysine head groups spontaneously self-assembles into a bimolecular micelle in water. This self-assembled structure was characterized by small angle X-ray scattering (SAXS), field flow fluctuation coupled with multi-angle light scattering (FFF-MALS) and atomic force microscopy (AFM). The self-assembly of amphiphilic pillar[5]arene into dimeric spherical micelles represents a new molecular architecture for micelle formation. This journal is © The Royal Society of Chemistry. Source


Okuzono T.,Oita University | Otsuru T.,Oita University | Tomiku R.,Oita University | Okamoto N.,Ariake National College of Technology
Journal of the Acoustical Society of America | Year: 2012

The applicability of the modified integration rule for time-domain finite-element analysis is tested in sound field analysis of rooms involving rectangular elements, distorted elements, and finite impedance boundary conditions. Dispersion error analysis in three dimensions is conducted to evaluate the dispersion error in time-domain finite-element analysis using eight-node hexahedral elements. The results of analysis confirmed that fourth-order accuracy with respect to dispersion error is obtainable using the Fox-Goodwin method (FG) with a modified integration rule, even for rectangular elements. The stability condition in three-dimensional analysis using the modified integration rule is also presented. Numerical experiments demonstrate that FG with a modified integration rule performs much better than FG with the conventional integration rule for problems with rectangular elements, distorted elements, and with finite impedance boundary conditions. Further, as another advantage, numerical results revealed that the use of modified integration rule engenders faster convergence of the iterative solver than a conventional rule for problems with the same degrees of freedom. © 2012 Acoustical Society of America. Source


Tanaka A.,Ariake National College of Technology | Tasaki H.,Gakushuin University
Journal of Statistical Physics | Year: 2016

We construct a multi-band Hubbard model on the lattice obtained by “decorating” a closely packed d-dimensional lattice M (such as the triangular lattice) where d≥ 2. We take the limits in which the Coulomb interaction and the band gap become infinitely large. Then there remains only a single band with finite energy, on which electrons are supported. Let the electron number be Ne= | M| - Nh, where | M| corresponds to the electron number which makes the lowest (finite energy) band half-filled, and Nh is the number of “holes”. It is expected that the model exhibits metallic ferromagnetism if Nh/ | M| is nonvanishing but sufficiently small. We prove that the ground states exhibit saturated ferromagnetism if Nh≤ (const.) | M| 2 / ( d + 2 ), and exhibit (not necessarily saturated) ferromagnetism if Nh≤ (const.) | M| ( d + 1 ) / ( d + 2 ). This may be regarded as a rigorous example of metallic ferromagnetism provided that the system size | M| is not too large. © 2016, Springer Science+Business Media New York. Source

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