In this work, we focus on three factors as regards information degradation in 4 Tbpsi heated-dot magnetic recording, namely, (1) the reduction in readout field strength due to dot area variation, (2) the reversal of the magnetization direction during 10 years of archiving due to thermal fluctuation, and (3) during adjacent track writing due to thermal fluctuation (adjacent track interference, ATI). We consider the full width at half maximum of the readout field as well as the peak value. The bit error rate bER as a function of the minimum normalized readout field H₀, that must be readable without error, is calculated using each dot error probability, taking account of dot area variation and thermal fluctuation. The H₀ value needed to achieve a certain bER is determined by dot area variation. There is a minimum dot height for a certain bER, which is determined by thermal fluctuation. Even if the dot height is increased, the H₀ value cannot be increased. Since temperature has a strong impact on dot error probability, a very large thermal gradient in the cross-track direction is needed to suppress ATI.

  A novel method for the rapid detection of bacteria in the liquid phase for point-of-care testing was developed using magnetic nanoparticles (MNPs) conjugated with antibodies. We utilized the magnetic characteristic that the magnetic susceptibility decreases when the magnetism of MNP aggregate changes from ferromagnetism to superparamagnetism after bacteria bind to MNPs through an antigen-antibody reaction (Nanomag-D, 500 nmφ, 0.2 μl/sample). The magnetic susceptibility of Fusobacterium nucleatum samples was measured using a lab-made detection setup. We found that the susceptibility depends on the concentration of Fusobacterium nucleatum with optical density (OD) values ranging from 10^-4 to 1 (i.e. 8 × 10⁴ ~ 8 × 10⁸ CFU/ml). In addition, the detection time was only about 49 seconds, which shows promise for point-of-care testing.

  Contact conveyance by rollers is used in thin steel-plate production lines, and scratches on the surface of the plates and plating defects may occur. Therefore, noncontact magnetic levitation conveyance of thin steel plates using the attractive force of electromagnets has been proposed. We previously studied a magnetic levitation system for thin steel plates using both electromagnets and permanent magnets. However, the vibration characteristics of levitated steel plates have not yet been studied. In this study, magnetic levitation experiments were conducted on steel plates using the optimum arrangement of permanent magnets for each condition obtained by the genetic algorithm, and the stability of levitation was experimentally investigated. The results confirmed that the levitation performance of the steel plates was different for each gap. As the gap increased and approached the optimum gap obtained in the GA search, the attractive force of the permanent magnet became appropriate for assisting levitation. This optimized arrangement of permanent magnets reduces the deflection of the levitated steel plate, and the vibration could be suppressed. Thus, the proposed method can change the vibration characteristics of a levitated steel plate and improve levitation stability.

  Ultra-compact electric vehicles (EVs) have been recently sold as next-generation vehicles. However, they are yet to reach a notable phase of expansion and use. Ultra-compact EVs have compact and lightweight bodies. As the outer plate of an ultra-compact EV has low rigidity, the road noise generated by the tires and the wind noise generated from the vehicle’s projection shape are transmitted to the interior of the vehicle. Therefore, a new active noise control (ANC) system with a giant magnetostrictive actuator for ultra-compact EVs has been recently proposed. The giant magnetostrictive actuator is required to produce sufficient thrust, with less distortion, and delayed sound waves. In this work, we studied the thrust force characteristics of the giant magnetostrictive material, including in the road noise range. We considered the giant magnetostrictive thrust for output, including in the road noise range, using a finite element model of the giant magnetostrictive actuator by conducting an electromagnetic field analysis. The results showed that the effect of the thrust on the frequency changes depending on the length of the giant magnetostrictive material.