University of Electro-Communications

About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.

Unconventional Pairing Originating from the Disconnected Fermi Surfaces of Superconducting LaFeAsO 1-x F x

Abstract: For a newly discovered iron-based high ${T}_{c}$ superconductor ${\mathrm{LaFeAsO}}_{1\ensuremath{-}x}{\mathrm{F}}_{x}$, we have constructed a minimal model, where inclusion of all five Fe $d$ bands is found to be necessary. The random-phase approximation is applied to the model to investigate the origin of superconductivity. We conclude that the multiple spin-fluctuation modes arising from the nesting across the disconnected Fermi surfaces realize an extended $s$-wave pairing, while $d$-wave pairing can also be another candidate.

Micromagnetic understanding of current-driven domain wall motion in patterned nanowires

Abstract: In order to explain recent experiments reporting a motion of magnetic domain walls (DW) in nanowires carrying a current, we propose a modification of the spin transfer torque term in the Landau-Lifchitz-Gilbert equation. We show that it explains, with reasonable parameters, the measured DW velocities as well as the variation of DW propagation field under current. We also introduce coercivity by considering rough wires. This leads to a finite DW propagation field and finite threshold current for DW propagation, hence we conclude that threshold currents are extrinsic. Some possible models that support this new term are discussed.

A multiple Lyapunov function approach to stabilization of fuzzy control systems

Abstract: This paper addresses stability analysis and stabilization for Takagi-Sugeno fuzzy systems via a so-called fuzzy Lyapunov function which is a multiple Lyapunov function. The fuzzy Lyapunov function is defined by fuzzily blending quadratic Lyapunov functions. Based on the fuzzy Lyapunov function approach, we give stability conditions for open-loop fuzzy systems and stabilization conditions for closed-loop fuzzy systems. To take full advantage of a fuzzy Lyapunov function, we propose a new parallel distributed compensation (PDC) scheme that feedbacks the time derivatives of premise membership functions. The new PDC contains the ordinary PDC as a special case. A design example illustrates the utility of the fuzzy Lyapunov function approach and the new PDC stabilization method.