Rare-earth transition-metal alloy thin films, which serve as crucial test specimens for creating ultrafast spintronics devices, have major composition and temperature dependencies of magnetization based on the ferrimagnetic model. Although the thickness dependency of magnetization characteristics is known even in thin film regions, this dependence is difficult to explain conventional models. This study systematically evaluated this thickness dependence and confirmed an inverse proportional trend with film thickness for two compositions. Based on these results, we propose a new model involving sublattice magnetization networks with volume difference. Using this model, we confirmed significantly suppresses the thickness dependence of magnetization in GdFeCo films which adjacent Gd thin films. Furthermore, we verified the validity of the model through the response of the all-optical magnetization switching phenomenon based on the sublattice magnetizations.
For example, a semiconductor element is turned off in a power supply circuit. A part of the circuit becomes an open-circuit. The magnetic energy stored by the parasitic inductance of the conductor line in the open-circuit is then released as circulating currents flowing within the conductor line. The circulating current flows symmetrically between the left and right sides of the conductor line, which is divided into two parts widthwise. The author clarified this circulating current by measuring the local magnetic field on the conductor line using the optical probe type magnetic field sensor. In addition, this paper describes in detail the current density distribution and the magnetic field of the circulating current in conductor lines of various cross-sectional shapes. The analysis results revealed that the integrated current density within the conductor line is zero regardless of the cross-sectional shape of the conductor line, but circulating currents flow. Also the magnetic field around a highly symmetric cylindrical conductor line is zero. On the other hand, the magnetic field increases as the aspect ratio increases, as in the case of a less symmetrical rectangular conductor line.
Three-dimensional numerical analysis is conducted to clarify the effect of wavy Taylor vortices on the power generation characteristics of a co-axial magnetohydrodynamic energy conversion device. The numerical results show that time-periodic oscillations in the input and output powers occur when the load factor, which is defined as the ratio of the load voltage to the induced electromotive force, is below a threshold. These are caused by the modulation of the wavy Taylor vortices induced inside the device. Additionally, the oscillation amplitude of the output power is considerably small even when the oscillation amplitude of the input power is maximum. The effects of Taylor vortices and Lorentz force on the input power are also investigated. The dependence of the input power on the load factor is determined by the balance between the contribution from inertial force (convection), which increases with increasing load factor, and the contribution from the Lorentz force, which decreases with increasing load factor.
ABSTRACT This paper proposes an advanced adaptive protection relay system that leverages IEC 61850‐based wide‐area communication and PLC‐driven decision logic. By integrating real‐time data from multiple substations, the system dynamically adapts relay operations to changing network topologies while maintaining compatibility with existing protection relays through an add‐on architecture. This add‐on approach facilitates easy deployment without major modifications to existing systems, enabling scalable and cost‐effective implementation. A decision tree algorithm provides transparent, deterministic, and rapid fault isolation. The proposed approach was validated through hardware‐in‐the‐loop simulations, demonstrating its practicality, scalability, and effectiveness in enhancing the reliability of power system protection.
This paper handles a workforce re-planning problem when an unplanned urgent task occurs and proposes a method to reduce the total outage duration of the plan. Recently, many enterprises have been introducing Field Service Management (FSM) system. FSM supports enterprises to list on-site tasks, manage progress of them, and plan workforce schedule for more efficient and faster work. It is expected to be utilized for power companies because they also have many on-site tasks such as managing assets/vegetation, replacing/fixing grid elements, and removing faluts. On-site tasks in the filed of power grids often require a planned outage to ensure safety for filed workforces. Thus, when an falut occurs, they have to stop their service due to the additional unplanned outage. This paper focuses on the ineffciency and proposes a method to bundle unplanned and planned outage by bringing forward planned tasks to the unplanned outage duration. The method was tested in two cases and confirmed that it can reduce the total outage duration or increase the number of planned tasks by appropriately setting the urgent task deadline in input task list.
