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Search Results: 1 - 10 of 1393 matches for " Hiroki Goda "
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Effect of Nitrite Ions on Steel Corrosion Induced by Chloride or Sulfate Ions
Zhonglu Cao,Makoto Hibino,Hiroki Goda
International Journal of Corrosion , 2013, DOI: 10.1155/2013/853730
Abstract: The influence of nitrite concentration on the corrosion of steel immersed in three simulated pH environments containing chloride ions or sulfate ions has been investigated by comparing and analyzing the change of half-cell potential, the change of threshold level of or , the change of threshold level of / or / mole ratio, and the changes of anodic/cathodic polarization curves and Stern-Geary constant . The corrosivity of chloride ions against sulfate ions also has been discussed in pH 12.6, pH 10.3, and pH 8.1 environments containing 0, 0.053, and 0.2?mol/L , respectively. 1. Introduction The corrosion of reinforcing steel in concrete has become one of the most severe deterioration mechanisms in concrete structures. It is generally accepted that due to the high alkalinity of cement hydration products, a protective layer of iron oxides is formed on the surface of steel, which provides adequate corrosion resistance. However, with the penetration of chloride, sulfate, and carbon dioxide and the appearance of concrete cracking, this protective layer becomes unstable and corrosion initials. As one of the methods is to prevent steel corrosion, nitrite-based corrosion inhibitors, irrespective of being directly added into concrete during the mixing process or penetrating into concrete by the surface-applied remedial treatment, have been widely investigated in chloride-contaminated concrete [1–3], carbonated concrete [4–6], and cracked concrete [7, 8], and their inhibiting efficiencies also have been checked in simulated concrete pore solution, such as in highly alkaline solution [9–12], carbonated solution [12–14], and neutral and acid solution [12, 15]. Most of these results confirm the effectiveness of nitrite in increasing the chloride threshold level, delaying the onset of corrosion, and reducing the corrosion rate once the corrosion was initiated, but there is no general consensus on the / mole ratio above that the preservation of the passive state can be ensured; suggested values for this threshold range from 0.11 to 1.0 in concrete and from 0.07 to greater than 2 in simulated pore solution. This difference in the threshold level of / mole ratio obtained from various literatures might be due to the way of determining the concentrations of chloride and nitrite in concrete (free ions and total ions, etc.), the different qualities of mortar and concrete used in the experiments, the different components of simulated pore solution, and the different surface topographies and compositions of the steel. Comparing and analyzing these literatures, the authors find
Effect of Water-Cement Ratio on the Macrocell Polarization Behavior of Reinforcing Steel
Zhonglu Cao,Makoto Hibino,Hiroki Goda
Journal of Engineering , 2014, DOI: 10.1155/2014/925410
Abstract: The effect of water-cement ratio on the macrocell polarization behavior of reinforcing steel embedded in cement mortars was investigated by comparing and analyzing the macrocell polarization ratios and slopes of anodic and cathodic steels. Based on the experimental results, the relationship between macrocell potential difference and macrocell current density was also analyzed, and the mechanism of macrocell polarization affected by water-cement ratio was proposed. The results indicated that the water-cement ratios had little impact on the macrocell polarization ratios of cathode and anode. The lower water-cement ratio could reduce the macrocell current by decreasing the macrocell potential difference and increasing the macrocell polarization resistance of the cathode and anode. 1. Introduction The water-cement ratio (W/C ratio) is one of the important parameters affecting the long-term properties of reinforced concrete. For cement pastes hydrated to the same degree, as the water-cement ratio decreases, the permeability of reinforced concrete decreases as well. The permeability of reinforced concrete is a critical factor limiting the penetration of chloride and the diffusion of carbon dioxide, oxygen, and other aggressive agents and therefore plays an important role in controlling the microcell and macrocell corrosion behaviors of reinforcing steel. According to the study of Arya and Vassie [1], for the same area ratio of cathode to anode, a lower water-cement ratio, and hence lower permeability, could decrease the macrocell current flowing between cathodic steel and anodic steel. This lower current obtained from the lower permeability mix could probably be explained by the higher resistance of concrete and the lower transport rate of oxygen and ferrous ions, producing restrictions to the cathode and anode reaction kinetics. Similar results could be confirmed by the study of Vedalakshmi et al. [2], Hansson et al. [3], and Ohno et al. [4–7]. The results of Raupach [8] indicated that a reduction of the water-cement ratio from 0.6 to 0.5 yielded a further reduction in steel mass loss in the crack zone. This influence was especially pronounced after 24 weeks and then became much smaller after one year, which might be explained by the fact that the period up to depassivation was prolonged by a reduction of the water-cement ratio. However, after the onset of corrosion, the water-cement ratio had only a negligible influence. All these studies as mentioned above only investigated the effect of water-cement ratio on the magnitude of macrocell current and did not
BNIP3 and NIX Mediate Mieap-Induced Accumulation of Lysosomal Proteins within Mitochondria
Yasuyuki Nakamura, Noriaki Kitamura, Daisuke Shinogi, Masaki Yoshida, Olga Goda, Ryuya Murai, Hiroki Kamino, Hirofumi Arakawa
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030767
Abstract: Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins. Here, we report that an additional mitochondrial outer membrane protein, BNIP3, is also involved in MALM. BNIP3 interacts with Mieap in a reactive oxygen species (ROS)-dependent manner via the BH3 domain of BNIP3 and the coiled-coil domains of Mieap. The knockdown of endogenous BNIP3 expression severely inhibited MALM. Although the overexpression of either BNIP3 or NIX did not cause a remarkable change in the mitochondrial membrane potential (MMP), the co-expression of all three exogenous proteins, Mieap, BNIP3 and NIX, caused a dramatic reduction in MMP, implying that the physical interaction of Mieap, BNIP3 and NIX at the mitochondrial outer membrane may regulate the opening of a pore in the mitochondrial double membrane. This effect was not related to cell death. These results suggest that two mitochondrial outer membrane proteins, BNIP3 and NIX, mediate MALM in order to maintain mitochondrial integrity. The physical interaction of Mieap, BNIP3 and NIX at the mitochondrial outer membrane may play a critical role in the translocation of lysosomal proteins from the cytoplasm to the mitochondrial matrix.
Servitization of Machine-Tool Trading Company to Value Orchestration Platform: Visualization of Japanese Integral-Modular Strategie  [PDF]
Kazuhiko Goda, Kyoichi Kijima
Journal of Service Science and Management (JSSM) , 2015, DOI: 10.4236/jssm.2015.83037
Abstract: It is controversial whether or not Japanese manufacturing is already in decline and the Japanese model of manufacturing that drove past decades of the industrial and economic growth has lost the power. It is though true that Japan needs to develop a new and innovative business model for manufacturing in the years ahead. The present paper aims at (1) arguing that Japanese manufacturing requires transformation from integral-technology-based to modular-technology-based as well as their co-existence and (2) visualizing strategies for supporting them in practical terms. We in particular claim that in the transformation Machine-Tool Trading (MTT) companies should play a crucial role in getting servitizatized and functioning as project producers. We discuss roles and functions to be expected from servitized MTT companies by using the value orchestration platform model with quality control 7 tools as a reference. We also illustrate a roadmap for an MTT company to be servitized based on some real observations as well as the authors’ experiences.
Learning from the First Step. Uni Mail in Geneva
Agnes Goda
Liber Quarterly : The Journal of European Research Libraries , 2002,
Abstract: In 1559 Jean Calvin established the Genevan Academy to train students in humanist learning in preparation for the ministry and positions in secular leadership. The first building of the Academy, the so called Auditoire de Calvin” still exists and is located next to St Peter’s Cathedral. Although law is also taught, the theological spirit remains predominant until the end of the 17th century.
Chinese Associations and the Making of Chinese Identities in Singapore (1819-1959)
Miho Goda
Kasarinlan : Philippine Journal of Third World Studies , 1998,
Abstract: The identity of the Chinese in Singapore took more than a century and half to develop. During British rule it began with one's place of origin and dialect or bang. The Chinese identity remained ethnically fragmented until the mainland became a republic. The emergence of communism was the next turning point as dissatisfied Chinese began identifying themselves as Singaporeans. These stages in the evolution and development of Chinese identities took place under the guidance of Chinese associations and the schools they established and managed in the Crown colony.
On the separability of multivariate functions
Takashi Goda
Mathematics , 2013,
Abstract: Separability of multivariate function alleviates the difficulty in finding a minimum or maximum value of a function such that an optimal solution can be searched by solving several disjoint problems with lower dimensionalities. In most of practical problems, however, a function to be optimized is black-box and we hardly grasp its separability on ahead. In this study, we first describe a general separability condition which a function defined over an arbitrary domain must satisfy if and only if that function is separable with respect to given disjoint subsets of variables. By introducing an alternative separability condition, we propose a Monte Carlo-based algorithm to estimate the separability of a function defined over unit cube with respect to given disjoint subsets of variables. Moreover, we extend our algorithm to estimate the number of disjoint subsets and disjoint subsets themselves such that a function is separable with respect to them. Computational complexity of our extended algorithm is function-dependent and varies from linear to exponential in the dimension.
Construction of scrambled polynomial lattice rules over $\mathbb{F}_2$ with small mean square weighted $\mathcal{L}_2$ discrepancy
Takashi Goda
Mathematics , 2013,
Abstract: The $\mathcal{L}_2$ discrepancy is one of several well-known quantitative measures for the equidistribution properties of point sets in the high-dimensional unit cube. The concept of weights was introduced by Sloan and Wo\'{z}niakowski to take into account the relative importance of the discrepancy of lower dimensional projections. As known under the name of quasi-Monte Carlo methods, point sets with small weighted $\mathcal{L}_2$ discrepancy are useful in numerical integration. This study investigates the component-by-component construction of polynomial lattice rules over the finite field $\mathbb{F}_2$ whose scrambled point sets have small mean square weighted $\mathcal{L}_2$ discrepancy. An upper bound on this discrepancy is proved, which converges at almost the best possible rate of $N^{-2+\delta}$ for all $\delta>0$, where $N$ denotes the number of points. Numerical experiments confirm that the performance of our constructed polynomial lattice point sets is comparable or even superior to that of Sobol' sequences.
Good interlaced polynomial lattice rules for numerical integration in weighted Walsh spaces
Takashi Goda
Mathematics , 2013,
Abstract: Quadrature rules using higher order digital nets and sequences are known to exploit the smoothness of a function for numerical integration and to achieve an improved rate of convergence as compared to classical digital nets and sequences for smooth functions. A construction principle of higher order digital nets and sequences based on a digit interlacing function was introduced in [J. Dick, SIAM J. Numer. Anal., 45 (2007) pp.~2141--2176], which interlaces classical digital nets or sequences whose number of components is a multiple of the dimension. In this paper, we study the use of polynomial lattice point sets for interlaced components. We call quadrature rules using such point sets {\em interlaced polynomial lattice rules}. We consider weighted Walsh spaces containing smooth functions and derive two upper bounds on the worst-case error for interlaced polynomial lattice rules, both of which can be employed as a quality criterion for the construction of interlaced polynomial lattice rules. We investigate the component-by-component construction and the Korobov construction as a means of explicit constructions of good interlaced polynomial lattice rules that achieve the optimal rate of the worst-case error. Through this approach we are able to obtain a good dependence of the worst-case error bounds on the dimension under certain conditions on the weights, while significantly reducing the construction cost as compared to higher order polynomial lattice rules.
Quasi-Monte Carlo integration using digital nets with antithetics
Takashi Goda
Mathematics , 2015,
Abstract: Antithetic sampling, which goes back to the classical work by Hammersley and Morton (1956), is one of the well-known variance reduction techniques for Monte Carlo integration. In this paper we investigate its application to digital nets over $\mathbb{Z}_{b}$ for quasi-Monte Carlo (QMC) integration, a deterministic counterpart of Monte Carlo, of functions defined over the $s$-dimensional unit cube. By looking at antithetic sampling as a geometric technique in a compact totally disconnected abelian group, we first generalize the notion of antithetic sampling from base $2$ to an arbitrary base $b\ge 2$. Then we analyze the QMC integration error of digital nets over $\mathbb{Z}_{b}$ with $b$-adic antithetics. Moreover, for a prime $b$, we prove the existence of good higher order polynomial lattice point sets with $b$-adic antithetics for QMC integration of smooth functions in weighted Sobolev spaces. Numerical experiments based on Sobol' point sets up to $s=100$ show that the rate of convergence can be improved for smooth integrands by using antithetic sampling technique, which is quite encouraging beyond the reach of our theoretical result and motivates future work to address.
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