The evaluation of the powder properties of the granule feed material for ferrite material production is very important. The fundamental properties of a powder are the packing characteristics and the flowability of the particle bed. In this study, we investigated the influence of the granule size distributions on the void fraction and the angle of repose of the granule particle bed. We found that the size distributions, which had the minimum values of the void fraction and the angle of repose.
The compression test of the ferrite granule particle bed was conducted by using a pellet test machine with the peculiar plunger and vessel.
Our results confirmed the correlations between the powder properties and its compression characteristics in the granule particle bed.

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Hard disk drives have been showing a 100% annual growth rate in areal recording density. In order to keep this rate in the future, we must overcome the thermal instability problem of the high-density magnetic recording media. Patterned media is a promising candidate for future high-density magnetic recording because it can improve thermal stability and reduce media transition noise. In this review a new method of fabricating patterned media with an artificially assisted self-assembled mask was described.

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The acoustic properties of (0-3) composite materials for acoustic matching layer of MHz-range air-coupled ultrasonic transducer are studied experimentally. The composite materials are formed from a mixture of silicone rubber and hollow thermoplastic microspheres. The acoustic properties of the composite materials are measured and compared with Reuss model, which is theoretical model for elastic properties of composite materials. The measured values of velocity and characteristic acoustic impedance of the composite materials agreed well with the theoretical estimation up to 10% weight fractions of hollow thermoplastic microspheres. The optimal value of characteristic acoustic impedance for acoustic matching layer of air-coupled ultrasonic transducer was calculated using transmission line model. The acoustic matching layer having the optimal value was obtained from the composite material, for which the weight percentage of hollow thermoplastic microspheres is 5%. Transmission of air-coupled ultrasonic wave of 1 MHz using piezoceramic transducer with the acoustic matching layer is demonstrated, and the sensitivity of transmission was improved by 10 dB using the optimal composite material.

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Specifications of patterned magnetic recording media for tera-bit recording were designed as an extension of perpendicular magnetic recording. Effective thermal stability of the magnetic dots with perpendicular anisotropy was estimated using the magnetic field where magnetization reversal begins in the magnetic dot array by the applied perpendicular field. The estimated magnetic properties of the media with an areal density of 1 Tbit/in² were expected to be realized with known hard magnetic materials such as Co-Pt and FePt alloys. Effects of the size and shape of dots and the spacing between dots on the magnetic reversal properties were investigated using a micromagnetic simulation. It was found that the spacing between dots would impose strong restriction on the achievable recording density. Recording simulation on a designed patterned medium indicated possibility of realization of 1 Tbit/in² recording.

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A prediction method for solubility parameters has been proposed based on a molecular structure. Solubility parameters δ₂₅ and molar volumes ν₂₅ at 25°C are estimated by using Fedors' additive methods of atomic groups. Further, molar volumes at t [°C] are also estimated by a group contribution method previously proposed by the authors. The solubility parameter at t [°C] is given by δ_t= (ν₂₅/ν_t) δ₂₅. The reliability is examined by adopting the present method to heptane and toluene.

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