Perpendicular Magnetic Recording Media on Various Hard-Disk Substrates
Co-Cr perpendicular media on rigid substrates were studied. We used untextured glass substrates for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard disk media deposited onto different substrates: untextured glass, silicon single crystal, chemically textured alumite, and Mn-Zn ferrite. We compared these substrates with respect to their crystallographic properties, head-to-medium spacing, and record/playback characteristics.
Faraday Rotation of Broad-Spectrum Polychromatic Light and Its Quantum Description
For polychromatic light having a broad spectrum width, the effective Faraday rotation angle ≪¿<inf>F</inf>≫ is defined operationally as ≪¿<inf>F</inf>≫ = ¿¿<sup>¿</sup><inf>F</inf>S<sup>¿</sup>P<sup>¿</sup>d¿/¿s<sup>¿</sup>p<sup>¿</sup>d¿. Here ¿<sup>¿</sup>, S<sup>¿</sup> and P<sup>¿</sup> are the Faraday rotation angle, photodetector sensitivity, and light intensity, respectively, at wavelength ¿. Integration is performed over the spectral width of the polychromatic light. From classical electromagnetic wave theory we derived the above equation, to which we gave a consistent quantum description of the photon image. Experiments on an FR-5 glass sample using a halogen lamp as a polychromatics light source supported our calculations.
Effect of superficial gas velocity on the particle temperature distribution in a fluidized bed with heat production
The heat transfer behavior of particles and gas in an olefin polymerization fluidized bed was numerically analyzed using an in-house developed 3-D computational fluid dynamics discrete element model (CFD-DEM). First the implementation of the model was verified by comparing simulation results with analytical results. A constant volumetric heat production rate was implemented in the particle energy equation to mimic the heat production due to the polymerization reaction. It was found that the probability density function (PDF) of the particle temperature becomes more homogeneous with increasing superficial gas velocity. Furthermore, instantaneous snapshots of the thermal driving force (the difference between the single particle temperature and bed-average gas temperature, Tp− ) for different heat production rates provide detailed insight in the particle temperature distribution inside the fluidized bed. The time- and bed-averaged particle convective heat transfer coefficient, which was calculated by Gunn׳s correlation, was found to be independent of the superficial gas velocity. This is explained by the fact that the relative velocity of gas and particles in the emulsion phase, where most of the particles and gas interact, is hardly influenced when increasing the gas superficial velocity. From the spatial distribution of Nusselt number, it becomes apparent that the high heat transfer regions are found in the wake of rising bubbles, whereas low heat transfer rates are found in the clouds of the bubbles.