A power management system is provided for a software-defined radio. The socket mount has a mount housing that carries a socket connector. The signal generator provides an operating signal in response to a selection signal. The top cover is formed therein with a concave and convex part for avoiding positioning a node of each of vibration modes caused by a critical rotating speed of the disc, at a position right above the optical head. The body portion has a plurality of inverted, truncated funnel members or baffles positioned therein in a vertically spaced-apart relationship which maintain a certain amount of feed at that level even though the main feed supply has dropped below that funnel member or baffle. The first and third raw slurries include inorganic fibers having a minimum diameter substantially greater than 3 micrometers.