Abstract: The present invention provides a lawn mower for cutting grass and maintaining the lawn surface. The lawn mower has a mower deck, a cutting blade driven by a motor, and a blade changing mechanism. The blade changing mechanism includes a fastener for securing the cutting blade to the motor, a blade securement tool for limiting the cutting blade from rotating, and at least one opening on the mower deck for removably receiving the blade securement tool. An edge guide is also provided on the mower deck. The lawn mower also includes a dynamic power management system configured to adjust a rotation speed of the motor dynamically based on a duty condition of the cutting blade.

Abstract: A method for finding a defective machine comprises the steps of selecting a searching period in which a plurality of wafer lots including good wafer lots and bad wafer lots passes through machines, acquiring a lot-passing information related to the passing sequence of the wafer lots through the machines, calculating a bad-lot continuity by taking the lot-passing information into account, and determining a defective machine by taking the bad-lot continuity into account. The bad-lot continuity is calculated by the steps of determining an impact period based on the aggregation degree of the bad wafer lots, calculating a bad-lot distribution probability in the impact period, and calculating the bad-lot continuity by taking the bad-lot distribution probability into account.