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In recent years, fresh fruits and vegetables have been sought after by Chinese people. The fresh-keeping technology, storage, and transportation of fruits and vegetables have also attracted a large number of people's attention. Various methods of preservation, storage, and transportation of fruits and vegetables have begun to appear in the society. Micro and nanobubbles have the characteristics of long stay time, larger than the surface, high surface negative electricity, strong reliability, high efficiency of heat transfer, can cause oxygen free radicals, can greatly improve the actual effect of ozone and ozone utilization rate, and reduce the operation cost. This article aims to study the application of ozone micro-nano bubble processing vegetable fresh-keeping technology in air logistics and transportation, and put forward the idea of applying ozone micro-nano bubble processing fresh-keeping technology to fruits and vegetables fresh-keeping and transportation more widely. This article focuses on the introduction of ozone micro-nano bubbles, fresh-keeping technology, air transportation, and experiments on some fresh-keeping technologies in the article. The experimental results show that the vegetable preservation technology based on ozone micro-nano bubbles can better maintain the moisture and nutrients in the vegetables. The preservation technology of ozone micro-nano bubble treatment has improved the preservation of fruits and vegetables by 12%. [ABSTRACT FROM AUTHOR]

Very high cycle fatigue behavior of nugget zone in AA 7075 friction stir welded joint was experimentally investigated using ultrasonic fatigue testing system (20 kHz) to clarify the crack initiation mechanism. It was found that the fatigue strength of nugget zone decreased continuously even beyond 107 cycles with no traditional fatigue limits. Fatigue cracks initiated from the welding defects located at the bottom side of the friction stir weld. Moreover, a special semicircular zone could be characterized around the crack initiation site, of which the stress intensity factor approximately equaled the threshold of fatigue crack propagation rate. Finally, a simplified model was proposed to estimate the fatigue life by correlating the welding defect size and applied stress. The predicted results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

On-line measuring device of cylindricity error is designed based on two-point method error separation technique (EST), which can separate spindle rotation error from measuring error. According to the principle of measuring device, the mathematical model of the minimum zone method for cylindricity error evaluating is established. Optimized parameters of objective function decrease to four from six by assuming that c is equal to zero and h is equal to one. Initial values of optimized parameters are obtained from least square method and final values are acquired by the genetic algorithm. The ideal axis of cylinder is fitted in MATLAB. Compared to the error results of the least square method, the minimum circumscribed cylinder method, and the maximum inscribed cylinder method, the error result of the minimum zone method conforms to the theory of error evaluation. The results indicate that the method can meet the requirement of engine cylinder bore cylindricity error measuring and evaluating. [ABSTRACT FROM AUTHOR]