Acoustics researchers at the Georgia Institute of Technology (www.me.gatech.edu) have developed a piezoceramic actuator to eliminate brake squeals that occur when a vehicle slows down and the brake pads contact the rotor, setting up a vibration that manifests itself as a high-pitched noise. Mounted inside the brake piston, the actuator can suppress the vibration by applying bursts of a 20-kHz dithering frequency—above the human hearing range—to the backing plate of the inside brake pad. An open-loop control system that is connected to the brake-light switch, the actuator does not need any detector or logic system to determine the proper control frequency.
The implementation of a new diesel fuel standard in the US has considerably improved the environmental performance of diesel vehicles. The Environmental Protection Agency (EPA) says that the new ultra-low sulfur diesel (ULSD) fuel has combined with other improved technologies to reduce diesel's particulate matter (PM) emissions by 99%.
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