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Abstract. When working, the geometric distribution shape of concrete in concrete mixing truck's rotary drum changes continuously, which cause a great difficulty for studying the dynamic performance of the mixing drum. In this paper, the mixing system of a certain type of concrete mixing truck is studied. A mathematical formulation has been derived through the force analysis to calculate the supporting force. The calculation method of the concrete distribution shape in the rotary drum is developed. A new transfer matrix is built with considering the concrete geometric distribution shape. The effects of rotating speed, inclination angle and concrete liquid level on the vibration performance of the mixing drum are studied with a specific example. Results show that with the increase of rotating speed, the vibration amplitude of the mixing drum decreases. The peak amplitude gradually moves to the right with the inclination angle increasing. The amplitude value of the peak's left side decreases when tilt angle increases, while the right side increases. The maximum unbalanced response amplitude of the drum increases with the decrease of concrete liquid level height, and the vibration peak moves to the left.

Tilt rotor supported by rolling bearings is often used in mechanical equipment. In the past, researches on dynamic performance of bearing-rotor were mainly carried out for horizontal rotor, but there is insufficient reported research on the tilting rotors. In this paper, the dynamic performance of a tilt rotor supported by spherical roller bearings is studied. Through the dynamics analysis of the rotor, a transfer matrix dynamics model for the tilt rotor is established. The stiffness and damping calculation model of spherical roller bearings is built. With a calculation example, the effects of tilting angles and some rotor structure parameters on the system's dynamic performance are studied numerically. The results obtained show that with the increase in the tilt angle, the critical speed of the rotor decreases, and the amplitude increases in the vertical direction of the shaft. With the same tilting angle, the smaller the distance from the disc to the middle point of the rotating shaft, the larger the amplitude of the vibration mode and the amplitude difference compared to that of the rotor without inclination. The unbalanced response amplitude curves of the rotor distribute asymmetrically because of the rotor's inclination. The bigger the inclination angle, the more obvious is the asymmetry distribution.

As we know, the TF method is more sensitive to changes in the power transformers at higher frequencies. Although measurement based on low voltage impulse (LVI) is definitely faster than that based on swept frequency method (SFM), the available frequency band is narrow because of the typical microsecond impulse. In this paper, the characteristics of the nanosecond impulse in the frequency domain were investigated. A test System based on Nanosecond low voltage impulse was developed. The proposed method was applied to a 10kV/100kVA distribution transformer in the laboratory. Measurement results with two different impulses were compared.