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This paper proposes a modified Reynolds equation for the coupled journal and thrust fluid dynamic bearings (FDBs) to include variable film thickness due to imperfect roundness of a rotating shaft. A finite element method is used to solve the modified Reynolds equation to calculate the pressure. Reaction force, moment, and friction torque of FDBs are calculated by integrating the pressure and shear stress along the fluid film. The dynamic behavior of a hard disk drive (HDD) spindle system is investigated by solving the equations of motion with six degrees of freedom using the Runge-Kutta method. This research shows that the imperfect roundness of the shaft increases the nonlinearity of FDBs. Imperfect roundness of the shaft generates harmonics of the groove number 1 in the bearing reaction force and the displacement of the HDD spindle system even in the case of stationary grooved FDBs.

The purpose of this work was to the application of Si oxide coatings. This study deals with the preparation of ceria(CeO 2 ) nanoparticles coating with SiO 2 by water glass and hydrolysis reaction. First, the low temperature hydro-reactions were carried out at 30~100°C. Second, Silicon oxide-coated Nano compounds were obtained by the catalyzing synthesis. CeO 2 Nano-powders have been successfully synthesized by means of the hydrothermal method, in a low temperature range of 100~200°C. In order to investigate the structure and morphology of the Nano-powders, scanning electron microscopy(SEM) and X-ray diffraction(XRD) were employed. The XRD results revealed the amorphous nature of silica nanoparticles. To analyze the quantity and properties of the compounds coated with Si oxide, transmission electron microscopy(TEM) in conjunction with electron dispersive spectroscopy was used. Finally, it is suggested that the simple growth process is more favorable mechanism than the solution/aggregation process.