Tiny ultrasonic linear actuators (TULAs) are used in many industrial applications and a full characterization of their dynamic behavior is needed. This paper presents a detailed theoretical-experimental study of TULAs. The general structure and operation principle of TULAs are introduced. The actuator dynamics is then described using a simple piezoelectric model. In practice, TULAs are most oft...

Discussion on improving our knowledge of changes in global poverty and inequality focused on three main questions. First, should international comparisons of living standards across countries use PPP estimates, or market exchange rates to compare the purchasing power of citizens in different countries? Second, if PPP estimates are used, is a single national measure of aggregate PPP adequate to ...