Nitrogen is an important fertilizer in tea production, but it is also an important factor in tea garden soil acidification. The relationship between absorption and transport of different forms of nitrogen in the tea plant and soil acidification is still unknown. In order to explore the different characteristics of absorption, utilization and distribution of nitrogen, stable isotope 15 N tracer technique was used to measure the absorption, utilization and allocation of nitrate nitrogen (NO 3 -15 N) and ammonium nitrogen (NH 4 -15 N) under the same nitrogen application amount of tea tree seedlings as experimental materials. The results showed that the tea seedlings had the same pattern of nitrogen application: tissue nitrogen content increased after fertilization, remarkable rising at 7 d and the absorption speed increased quickly after 28 d, finally reached its maximum at 56 d. The nitrogen use efficiency of two nitrogen sources in two kinds of soil varied not significantly. The maximum NUE of NO 3 -15 N reached 12.66%, and at the same time NH 4 -15 N utilization rose up to 11.54%. According to the absorption of soil nitrogen and nitrogen fertilizer in the two kinds of soil, it is concluded that the soil nitrogen cannot meet the growth needs of tea tree and extra nitrogen supply was required. The declined soil pH indicated that fertilizer should be used in moderation, which can not only satisfy the growth of tea tree but also to restrict soil acidification.
In this paper, the fuzzy control strategy is introduced, and then it proposes a two-dimensional fuzzy control method which takes the tractor driving wheel slip ratio and the engine throttle opening as input variables, while uses gear correction as output variable. Based on these, a fuzzy controller is designed to optimize the law of downshifting of tractor AMT. Subsequently, a best tractor AMT shift rule is formed through optimal combination of resolution obtained by the law of up-shifting. At last, simulation analysis is made on the basis of the simulation model established of tractor AMT shifting process. The results show that shift cycle can be effectively avoided and shift shock will reduced in the process of shifting, which makes the quality of shifting better and greatly improve the performance of the tractor.
Based on the analysis of the characteristics of tractor clutch and the engagement process at start-up working condition, the dynamics model of the clutch start-up working condition is established, then clutch engaging control approaches are discussed with emphasis, therefore the clutch engaging control law of “fast-slow-fast” is obtained. According to the clutch control strategy, clutch simulating analysis of an AMT tractor at the starting conditions will be in process by Matlab/Simulink on the basis of well design of fuzzy controller. The analysis result shows that the use of fuzzy control theory could effectively control the engagement process of AMT tractor clutch at start-up working condition.
In the manufacturing and production of hypoid gears, it is a necessary key problem to improve the tooth surface heat treatment precision and production efficiency of the hypoid gears. How to use advanced statistical theory and methods to evaluate the whole batch machining quality of the tooth surface after heat treatment is particularly urgent. In this connection, for the same batch of hypoid gears with the same gear material, numerical control gear milling method, and heat treatment specifications, a bootstrap-based statistics scheme of tooth surface errors after heat treatment is proposed in this paper. The bootstrap statistics model of the tooth surface errors for the batch hypoid gears is established. The bootstrap probability eigenvalues and confidence intervals of the measurement sequence points on the tooth surface errors are solved, and the optimizing selection of the single sampling numbers and the repeated sampling times is completed. On this basis, by applying the cubic NURBS surface fitting method, the mean value difference surface of the batch tooth surface errors data is constructed, the statistics laws of the whole batch tooth surface errors after heat treatment is determined, and the effective evaluation of the whole batch tooth surface accuracy is realized. Finally, the feasibility and correctness of the bootstrap-based statistics scheme are verified by the tooth surface errors bootstrap statistics application experiment of one kind of hypoid gear. The results show that with the help of the bootstrap statistics method proposed in this paper, it is not necessary to accurately measure the tooth surface errors of the whole batch of hypoid gears one by one. Only by randomly selecting 10 tooth surface samples and repeatedly sampling 2000 times, the original sample characteristic values of the whole batch tooth surface errors can be accurately estimated, and the heat treatment deformation statistics laws of the whole patch tooth surfaces can be also counted.
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