No abstract

Traveling wave rotary ultrasonic motor with double vibrators can improve the output performance effectively. However, the rotor has to be energized through a slip ring, which increases the complexity and reduces the reliability. Inheriting the concept of two traveling waves propagating in the stator and rotor, a dual traveling wave rotary ultrasonic motor energized only in the stator is proposed. By analyzing the oscillatory differential equation and the contact particles motion, a traveling wave is found in the rotor and the drive mechanism of dual traveling wave is studied. With the resonant rotor adopted, the consistent eigenfrequencies are calculated by finite element method and verified by an impedance analyzer. The performance experiment presents that the dual traveling wave rotary ultrasonic motor is superior to the motor with single traveling wave. The no-load speed is 60 rpm and the stalling torque is 0.85 Nm. Additionally, compared with a reported motor with double vibrators, the proposed motor presents the better output performance and the simpler design.

SUMMARYThis paper presents the results of pyrolysis experiments of the mixtures of nine different combustibles municipal solid wastes (MSW's main composition: rice 24.33% and fruits 14.60%). The experiments were carried out in a laboratory-scale reactor under nitrogen atmosphere at temperature of 300-7008C. The study concentrates on low-temperature pyrolysis of MSWs and the effect of the pyrolysis temperature on the characteristics of the products (solid fuels) including proximate analysis, volatile content, heating value, ignition temperature and density of the solid fuel. The results indicate that the pyrolysis temperature plays an important role on the characteristics of the solid fuels. The volatile content of the solid fuels decreases with the pyrolysis temperature so that the low-pyrolysis MSW treating process has advantage for higher heating value of the solid fuel for energy recovery purpose. The heating value is in the range of 23-27 MJ kg À1, equivalent to the heating value of low-rank coals.

Piezoelectric actuators based on bridge displacement amplifying mechanisms are widely used in precision driving and positioning fields. The classical bridge mechanism relies on structural flexibility to realize the return stroke, which leads to the low positioning accuracy of the actuator. In this paper, a series bridge mechanism is proposed to realize a bidirectional active drive; the return stroke is driven by a piezoelectric stack rather than by the flexibility of the structure. By analyzing the parameter sensitivity of the bridge mechanism, the series actuation of the bridge mechanism is optimized and the static and dynamic solutions are carried out by using the finite element method. Compared with the hysteresis loop of the piezoelectric stack, the displacement curve of the proposed actuator is symmetric, and the maximum nonlinear error is improved. The experimental results show that the maximum driving stroke of the actuator is 129.41 μm, and the maximum nonlinear error is 5.48%.

No abstract