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Tokyo, Japan

Aoyama Gakuin University , abbreviated AGU, is a Japanese Christian university in Shibuya near Omotesandō, Tokyo, Japan. Aoyama Gakuin University is part of a comprehensive educational institute called Aoyama Gakuin, which includes a kindergarten, an elementary school, junior and senior high schools, and a women's junior college. Aoyama Gakuin's history dates from October 1874, when missionaries from the Methodist Episcopal Church of the United States established three schools. John Franklin Goucher contributed to the establishment of the university. Canadian Methodist missionary Davidson MacDonald played a role in the establishment of Aoyama Gakuin, and his contribution to the improvement of Japan's educational system is considered an important episode in the early history of Japanese-Canadian relations. The institution took its present form in 1949 when Aoyama Gakuin College was established as a comprehensive university.Aoyama Gakuin University is one of the most prestigious private universities in Japan.The university's undergraduate and graduate programs include "literature", "law", "economics", "business", "international politics, economics and communication", "science and engineering","cultural and creative studies". The university also has specialized graduate programs that are designed to train high level specialized professionals, including "international management", "law school", and "professional accounting". Wikipedia.

Ohira Y.,Aoyama Gakuin University
Physical Review Letters | Year: 2013

Perpendicular collisionless shocks propagating into partially ionized plasmas are investigated by two-dimensional hybrid particle simulations. It is shown that some neutral particles leak into the upstream region from the downstream region, the leaking neutral particles become pickup ions in the upstream region and modify the shock structure, the pickup ions are preferentially accelerated, and plasma instabilities are excited by the pickup ions in the upstream and downstream regions. © 2013 American Physical Society. Source

Yoneyama J.,Aoyama Gakuin University
Fuzzy Sets and Systems | Year: 2013

This paper is concerned with robust H∞ filtering for Takagi-Sugeno sampled-data fuzzy systems with uncertain parameters. Takagi-Sugeno fuzzy system can describe a wide class of nonlinear systems, and is widely used in many engineering fields. Recently, system analysis and control design for nonlinear systems based fuzzy system approach have been active. The system is usually modelled as a continuous-time system, while in practical situations the observation is taken at discrete instants. Such an observation can be represented as a delayed signal. First it is shown that the error system which stems from an original fuzzy system and a sampled-data filter becomes a system with time-varying delay. Sufficient conditions for the error system to achieve the robust stability with H∞ disturbance attenuation are given in terms of linear matrix inequalities(LMIs). We derive such conditions via output delay system approach under the assumption that sampling-time is not greater than some prescribed number. Based on such conditions, we propose a robust H∞ sampled-data filter design for a fuzzy system. We consider two different cases for the premise variables in our filter design. Numerical examples are given to illustrate our robust H ∞ sampled-data filtering. © 2012 Elsevier B.V. Source

Inoue T.,Aoyama Gakuin University | Inutsuka S.-I.,Nagoya University
Astrophysical Journal | Year: 2012

Using three-dimensional magnetohydrodynamic simulations, including the effects of radiative cooling/heating, chemical reactions, and thermal conduction, we investigate the formation of molecular clouds in the multi-phase interstellar medium. As suggested by recent observations, we consider the formation of molecular clouds due to accretion of H I clouds. Our simulations show that the initial H I medium is piled up behind the shock waves induced by accretion flows. Since the initial medium is highly inhomogeneous as a consequence of thermal instability, a newly formed molecular cloud becomes very turbulent owing to the development of the Richtmyer-Meshkov instability. The kinetic energy of the turbulence dominates the thermal, magnetic, and gravitational energies throughout the entire 10 Myr evolution. However, the kinetic energy measured using CO-fraction-weighted densities is comparable to the other energies, once the CO molecules are sufficiently formed as a result of UV shielding. This suggests that the true kinetic energy of turbulence in molecular clouds as a whole can be much larger than the kinetic energy of turbulence estimated using line widths of molecular emission. We find that clumps in a molecular cloud show the following statistically homogeneous evolution: the typical plasma β of the clumps is roughly constant 〈β〉 ≃ 0.4; the size-velocity dispersion relation is Δv ≃ 1.5 km s-1 (l/1 pc)0.5, irrespective of the density; the clumps evolve toward magnetically supercritical, gravitationally unstable cores; and the clumps seem to evolve into cores that satisfy the condition for fragmentation into binaries. These statistical properties may represent the initial conditions of star formation. © 2012. The American Astronomical Society. All rights reserved.. Source

Ohira Y.,Aoyama Gakuin University
Astrophysical Journal | Year: 2012

In this paper, we investigate effects of neutral particles on shocks propagating into the partially ionized medium. We find that for 120 km s -1 < ush < 3000 km s-1 (ush is the shock velocity), about 10% of upstream neutral particles leak into the upstream region from the downstream region. Moreover, we investigate how the leakage neutral particles affect the upstream structure of the shock and particle accelerations. Using four-fluid approximations (upstream ions, upstream neutral particles, leakage neutral particles, and pickup ions), we provide analytical solutions of the precursor structure due to leakage neutral particles. It is shown that the upstream flow is decelerated in the precursor region and the shock compression ratio becomes smaller than without leakage neutral particles, but the total compression ratio does not change. Even if leakage of neutral particles is small (a few percent of total upstream particles), this smaller compression ratio of the shock can explain steep gamma-ray spectra from young supernova remnants. Furthermore, leakage neutral particles could amplify the magnetic field and heat the upstream region. © 2012. The American Astronomical Society. All rights reserved. Source

Inoue T.,Aoyama Gakuin University
Astrophysical Journal | Year: 2012

The linear stability of a current sheet that is subject to an impulsive acceleration due to shock passage with the effect of a guide magnetic field is studied. We find that a current sheet embedded in relativistically magnetized plasma always shows a Richtmyer-Meshkov-type instability, while the stability depends on the density structure in the Newtonian limit. The growth of the instability is expected to generate turbulence around the current sheet, which can induce the so-called turbulent reconnection, the rate of which is essentially free from plasma resistivity. Thus, the instability can be applied as a triggering mechanism for rapid magnetic energy release in a variety of high-energy astrophysical phenomena such as pulsar wind nebulae, gamma-ray bursts, and active galactic nuclei, where the shock wave is thought to play a crucial role. © 2012. The American Astronomical Society. All rights reserved. Source

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