RESUMO
A novel small-load fatigue testing device whose actuation resource is the piezoelectric material is proposed. The procedure of energy conversion and motion transfer is analyzed in detail. In the experiment by which the characteristic of the fatigue testing device is tested, the testing device works at resonance and the amplitude of the output could be up to 6.3 mm and output force is in the range of 0.6-2.5 N when the actuation frequency is higher than 100 Hz. The article presents the details of a piezoelectric device that is superior not only in smaller output force and higher testing frequency but also in high resolution, quick response, small scale, no noise, and anti-electromagnetic interference. The research about this kind of testing device benefits increasing the testing efficiency and development of a new material.
RESUMO
In order to improve the output capacity of a piezoelectric pump when transferring gas, this paper presents a compact resonant piezoelectric diaphragm pump (hereinafter referred to as the piezoelectric diaphragm pump), which is driven by a rectangular piezoelectric vibrator. The compact structure can effectively release the vibrating constraints of the vibrator, and enlarge its center output displacement, so as to increase the volume change rate of the pump chamber. Based on the structure and the working principle of this piezoelectric diaphragm pump, a dynamic model for the diaphragm system is established in this paper, and an analysis on factors affecting the resonant frequency of the system is then conducted. We tested on the prototype under the driving voltage of 260 Vpp. The results show that the diaphragm system reaches resonance under the driving frequency of 265 Hz, which is very close to the fundamental frequency of check valve. Compared with the rectangular piezoelectric vibrator's amplitude, the diaphragm's amplitude is double amplified. At this time, the piezoelectric diaphragm pump achieves the maximum gas flow rate as 186.8 mL/min and the maximum output pressure as 56.7 kPa.
RESUMO
An energy-saving ethanol fermentation technology was developed using uncooked fresh sweet potato as raw material. A mutant strain of Aspergillus niger isolated from mildewed sweet potato was used to produce abundant raw starch saccharification enzymes for treating uncooked sweet potato storage roots. The viscosity of the fermentation paste of uncooked sweet potato roots was lower than that of the cooked roots. The ethanol fermentation was carried out by Zymomonas mobilis, and 14.4 g of ethanol (87.2% of the theoretical yield) was produced from 100g of fresh sweet potato storage roots. Based on this method, an energy-saving, high efficient and environment-friendly technology can be developed for large-scale production of fuel ethanol from sweet potato roots.