Aoyama Gakuin University

About: Aoyama Gakuin University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Superconductivity & Thin film. The organization has 3494 authors who have published 6419 publications receiving 115648 citations. The organization is also known as: Aoyama gakuin daigaku.

The ‘amplitude’ parameter of gamma-ray bursts and its implications for GRB classification

Abstract: Traditionally gamma-ray bursts (GRBs) are classified in the $T_{90}$-hardness ratio two-dimensional plane into long/soft and short/hard GRBs. In this paper, we suggest to add the "amplitude" of GRB prompt emission as the third dimension as a complementary criterion to classify GRBs, especially those of short durations. We define three new parameters $f$, $f_{\rm eff}$ and $f_{\rm eff,z}$ as ratios between the measured/simulated peak flux of a GRB/pseudo-GRB and the flux background, and discuss the applications of these parameters to GRB classification. We systematically derive these parameters to find that most short GRBs are likely not "tip-of-iceberg" of long GRBs. However, one needs to be cautious if a short GRB has a relatively small $f$ (e.g. $f<1.5$), since the chance for an intrinsically long GRB to appear as a "disguised" short GRB is higher. Based on avaialble data, we quantify the probability of a disguised short GRB below a certain $f$ value is as $P (

Fermi large area telescope observations of the cygnus loop supernova remnant

Abstract: We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is {approx} 1 x 10{sup 33} erg s{sup -1} between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 {+-} 0{sup o}.1 and 1{sup o}.6 {+-} 0{sup o}.1. Given the association among X-ray rims, H{alpha} filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

Chiral helimagnetism in T1/3NbS2 (T=Cr and Mn)

Abstract: We report commensurate-to-incommensurate (C–IC) magnetic ordering in T1/3NbS2 (T=Cr and Mn), of which space group is P6322. We measured the anisotropic magnetization under magnetic fields applied perpendicular and parallel to the hexagonal c-axis. We observed a magnetization anomaly, only when the magnetic field was applied perpendicular to the hexagonal c-axis. The experimental results were in good agreement with the theoretical prediction based on a lattice chiral XY model, which describes the C–IC transition as chiral soliton formation. Therefore, we propose that the magnetic ordering in an incommensurate phase of T1/3NbS2 (T=Cr and Mn) can be chiral helimagnetic.

Tensile behavior of friction-stir welded AZ31 magnesium alloy

Abstract: In this work, electron backscatter diffraction (EBSD) and digital image correlation were employed to study tensile behavior of friction-stir welded magnesium alloy AZ31. The character of measured strain patterns indicated the prevalence of basal slip but also suggested significant activity of prism slip. A substantial strain gradient was found lengthways in the stir zone. The failure was shown to be initiated at the weld root and to originate from double { 10 1 ¯ 1 } − { 10 1 ¯ 2 } twinning. Crack propagation was influenced by the “onion-ring structure” of the stir zone.