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Search Results: 1 - 10 of 944 matches for " Akihiro Iwase "
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The Corrosion Behavior of Ni3Al/Ni3V Two-Phase Intermetallic Compounds in Various Acidic Solutions
Gadang Priyotomo,Hideyuki Momono,Sanat Wagle,Kenji Okitsu,Akihiro Iwase,Yasuyuki Kaneno,Rokuro Nishimura,Takayuki Takasugi
International Journal of Corrosion , 2012, DOI: 10.1155/2012/626240
Abstract: The corrosion behavior of the Ni3Al/Ni3V two-phase intermetallic compounds with and without minor elements (Nb, Co, and Cr) to be composed of L12 phase (Ni3Al) and a mixed phase of L12 (Ni3Al) and D022 (Ni3V) has been investigated by using an immersion test in 0.5?kmol/m3 HCl, H2SO4, and HNO3 solutions. The surface morphology was observed before and after the immersion test by scanning electron microscope (SEM). The results were compared to those of the L12 single-phase Ni3(Si,Ti) and austenitic stainless steel type 304. In all acidic solutions, preferential dissolution of ( ) phase was found in Ni3Al/Ni3V, but no intergranular attack, whereas the attacks took place on Ni3(Si,Ti). The Ni3Al/Ni3V showed a higher corrosion resistance in HCl solution and a lower resistance in HNO3 solution than Ni3(Si,Ti) and type 304. The addition of the minor elements enhanced corrosion resistance in HNO3 solution, but not clearly in HCl and H2SO4 solutions. In HCl and H2SO4, their weight losses during the immersion test were almost the same. 1. Introduction Recently, Ni-Al-V intermetallic compounds with a two-phase microstructure of Ni3Al (L12) and Ni3V (D022) phases have been developed by Takasugi et al. [1–13] and are confirmed to exhibit a highly coherent interface between these constituent phases. They have superior mechanical properties (i.e., high creep rapture life, high hardness, low thermal expansion, and better thermal conductivity) and also have high tensile strength and fracture toughness over a broad range of temperature in comparison with those of Inconel 750, Inconel 718 and Hastelloy [1–13]. Therefore, the Ni3Al/Ni3V two-phase intermetallic compounds are a candidates as materials in land-based, marine-based, and aero-gas turbine industries (turbine blade), high strength nut and bolt, and high temperature bearing or high temperature tool [8, 9, 14]. However, many studies revealed that the intermetallic compounds containing aluminum are very susceptible to hydrogen embrittlement [15–18], where hydrogen embrittlement takes place with permeation of atomic hydrogen formed by corrosion reaction into the compounds. Hence, to suppress this environmental embrittlement a small amount of boron was added to these compounds. However, it was reported that the boron segregation at grain boundaries became the preferential dissolution site and led to the intergranular attack in the L12 single-phase Ni3(Si,Ti) [19]. Furthermore, Ni base intermetallic compounds such as single-phase Ni3(Si,Ti) have attractive properties for high-temperature structural material (e.g., high
Oxygen uptake, heart rate, and work rate at ventilatory threshold for treadmill walking against a horizontal impeding force  [PDF]
Akihiro Azuma
Health (Health) , 2013, DOI: 10.4236/health.2013.512269

The purpose of this study was to compare the ventilatory threshold (VT) between treadmill walking against a horizontal impeding force (horizontal load walking) and a cycle ergometer exercise. Seven adult men volunteered to participate in this study. They performed horizontal load walking (velocity: 1.11 m/s) and a cycle ergometer exercise (pedaling frequency: 60 rpm), with loads imposed using a ramp slope technique. Oxygen uptake at the VT during horizontal load walking was greater than that during a cycle ergometer exercise (p < 0.05), whereas the opposite was noted for the work rate at VT (p < 0.05). The greater metabolic cost was because of the small output (work rate at VT) incurred during horizontal load walking. This suggested that the muscle mass recruited for exercise would be much greater for horizontal load walking than a cycle ergometer exercise because pedaling requires fewer muscles (lower extremities). In addition, a high reliability of VT during horizontal load walking was indicated from the correlation coefficient, standard error, and the confidence coefficient in two trials for the same subjects, which were 0.97, 0.097 L/min, and 0.96, respectively. These results suggest that horizontal load walking may be a modality for aerobic conditioning.


Affine Eikonal, Wavization and Wigner Function  [PDF]
Akihiro Ogura
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.713156
Abstract: The aim in this paper is to construct an affine transformation using the classical physics analogy between the fields of optics and mechanics. Since optics and mechanics both have symplectic structures, the concept of optics can be replaced by that of mechanics and vice versa. We list the four types of eikonal (generating functions). We also introduce a unitary operator for the affine transformation. Using the unitary operator, the kernel (propagator) is calculated and the wavization (quantization) of the Gabor function is discussed. The dynamic properties of the affine transformed Wigner function are also discussed.
Classical and Quantum Behavior of Generalized Oscillators in Terms of Linear Canonical Transformations  [PDF]
Akihiro Ogura
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.715191
Abstract: The quantum mechanical relationships between time-dependent oscillators, Hamilton-Jacobi theory and an invariant operator are clarified by making reference to a system with a generalized oscillator. We introduce a linear transformation in position and momentum, and show that the correspondence between classical and quantum transformations is exactly one-to-one. We found that classical canonical transformations are constructed from quantum unitary transformations as long as we are concerned with linear transformations. We also show the relationship between the invariant operator and a linear transformation.
Diagrammatic Approach for Investigating Two Dimensional Elastic Collisions in Momentum Space I: Newtonian Mechanics  [PDF]
Akihiro Ogura
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.89025
Abstract: We present the usefulness of the diagrammatic approach for analyzing two dimensional elastic collision in momentum space. In the mechanics course, we have two major purposes of studying the collision problems. One is that we have to obtain velocities of the two particles after the collision from initial velocities by using conservation laws of momentum and energy. The other is that we have to study two ways of looking collisions, i.e. laboratory system and center-of-mass system. For those two major purposes, we propose the diagrammatic technique. We draw two circles. One is for the center-of-mass system and the other is for the laboratory system. Drawing these two circles accomplish two major purposes. This diagrammatic technique can help us understand the collision problems quantitatively and qualitatively.
Diagrammatic Approach for Investigating Two Dimensional Elastic Collisions in Momentum Space II: Special Relativity  [PDF]
Akihiro Ogura
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.89026
Abstract: The diagrammatic approach to the collision problems in Newtonian mechanics is useful. We show in this article that the same technique can be applied to the case of the special relativity. The two circles play an important role in Newtonian mechanics, while in the special relativity, we need one circle and one ellipse. The circle shows the collision in the center-of-mass system. And the ellipse shows the collision in the laboratory system. These two figures give all information on two dimensional elastic collisions in the special relativity.
Associahedra, Multiplihedra and units in $A_{\infty}$ form
Norio Iwase
Mathematics , 2012,
Abstract: Jim Stasheff gave two apparently distinct definitions of an $A_{m}$ form, $m \leq \infty$ in [15,16]. It is also claimed that the two definitions are equivalent in [15,16], while it is not apparently clear for us. That is why we are trying to clarify related things and to show that the claim is actually true under a `loop-like' hypothesis in this paper. Along with these two definitions, we must construct Associahedra and Multiplihedra as convex polytopes with piecewise-linearly decomposed faces to manipulate units in $A_{\infty}$ form. This is done in Iwase [8,9], Iwase-Mimura [10] or by Haiman [7] especially on Associahedra, followed recently by Forcey [6] and Mau-Woodward [12], while the origin of Associahedra goes back to Tamari [17]. In this paper, we follow [10] on the geometric constructions of Associahedra and Multiplihedra. In Appendix, we also explain how we can construct Associahedra or Multiplihedra as polytopes on the (half) lattice by taking a shadow or collecting words from trivalent or bearded trees.
A_{\infty}-method in Lusternik-Schnirelmann category
Norio Iwase
Mathematics , 2002,
Abstract: To clarify the method behind the paper "Ganea's conjecture on Lusternik-Schnirelman category" by the author, a generalisation of Berstein-Hilton Hopf invariants is defined as `higher Hopf invariants'. They detect the higher homotopy associativity of Hopf spaces and are studied as obstructions not to increase the LS category by one by attaching a cone. Under a condition between dimension and LS category, a criterion for Ganea's conjecture on LS category is obtained using the generalised higher Hopf invariants, which yields the main result of "Ganea's ..." for all the cases except the case when $p=2$. As an application, conditions in terms of homotopy invariants of the characteristic maps are given to determine the LS category of sphere-bundles-over-spheres. Consequently, a closed manifold $M$ is found not to satisfy Ganea's conjecture on LS category and another closed manifold $N$ is found to have the same LS category as its `punctured submanifold' $N-\{P\}$, $P \in N$. But all examples obtained here support the conjecture in "Ganea's ...".
Lusternik-Schnirelmann category of a sphere-bundle over a sphere
Norio Iwase
Mathematics , 2002,
Abstract: A criterion to determine the L-S category of a total space of a sphere-bundle over a sphere is given in terms of homotopy invariants of its characteristic map, and thus providing a complete answer to Ganea's Problem 4. As a result, we obtain a necessary and sufficient condition for such a total space $N$ to have the same L-S category as its `once punctured submanifold' $N\smallsetminus\{P\}$, $P \in N$. Also a necessary condition for such a total space $M$ to satisfy Ganea's conjecture is obtained.
Evaluation of Carbon Dioxide Absorption Characteristics Lithium Ortho-Silicate in Chemical Heat Storage  [PDF]
Takehiro Esaki, Daichi Iwase, Noriyuki Kobayashi
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.54006
Abstract: We report the development of technology that may contribute to a reduction in greenhouse gas emissions and improve the energy efficiency of the CO2 capture process. Lithium ortho-silicate is a suitable solid sorbent for capturing CO2. This reversible chemical reaction is also applicable to chemical heat storage. The absorption reaction characteristics of lithium ortho-silicate were studied by a thermogravimetric method and a volumetric method that demonstrated the influence of heat and mass transfer limitations in a packed bed designed to be as small as possible. We developed a method for measuring the absorption reaction characteristics in the experiments. In the experiments, a constant conversion fraction of 60% was observed. The reaction system was stable to repetition. The CO2 absorption rate depends on the CO2 pressure and reactor temperature. The absorption rate was determined at several reactor temperatures when the conversion fraction was 0.3. In this study, the maximum absorption rate was obtained at 670oC. It was demonstrated that lithium ortho-silicate is suitable for use in a chemical heat storage system.
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