Utsunomiya University

About: Utsunomiya University is a education organization based out in Utsunomiya, Japan. It is known for research contribution in the topics: Laser & Holography. The organization has 4139 authors who have published 6812 publications receiving 91975 citations. The organization is also known as: Utsunomiya daigaku.

Stability analysis of nonlinear power electronic systems utilizing periodicity and introducing auxiliary state vector

Abstract: Variable-structure piecewise-linear nonlinear dynamic feedback systems emerge frequently in power electronics. This paper is concerned with the stability analysis of these systems. Although it applies the usual well-known and widely used approach, namely, the eigenvalues of the Jacobian matrix of the Poincare/spl acute/ map function belonging to a fixed point of the system to ascertain the stability, this paper offers two contributions for simplification as well that utilize the periodicity of the structure or configuration sequence and apply an alternative simpler and faster method for the determination of the Jacobian matrix. The new method works with differences of state variables rather than derivatives of the Poincare/spl acute/ map function (PMF) and offers geometric interpretations for each step. The determination of the derivates of PMF is not needed. A key element is the introduction of the so-called auxiliary state vector for preserving the switching instant belonging to the periodic steady-state unchanged even after the small deviations of the system orbit around the fixed point. In addition, the application of the method is illustrated on a resonant dc-dc buck converter.

Theoretical study of crystal and electronic structures of BiI3

Abstract: The electronic band structure as well as the crystal structure of the BiI3 semiconductor is investigated by performing first-principles pseudopotential calculations for the space group D3d1 or C3i2. The optimized structures were determined through total-energy calculations. The calculated results indicate that a rhombohedral structure (C3i2) forms a flatter band at the bottom of the conduction bands as compared to a hexagonal structure (D3d1). The lattice relaxation of the iodine atoms around a vacant site on the atomic plane of bismuth is found to play an important role on the conduction band bottom. It is proved that the rhombohedral BiI3 is an indirect semiconductor, while the hexagonal BiI3 has a direct band gap.

A Significant Method for Estimation of the Grain Size of Polycrystalline Materials

Abstract: A method has been proposed to estimate the grain size, which is defined as the grain size distribution in three dimensions, from the measured distribution of linear intercept length. The method is developed on the assumption that the grain size distribution is log normal in three dimensions. The three-dimensional grain size distribution is expressed as that of the «grain diameter» D defined as the equivalent volume diameter; the distribution of D is estimated from In D g and In σ g , (where D g is the geometric mean of D and σ g is the geometric standard deviation for D)