Based on the plane equivalent pitch curve of elliptical bevel gear,the pressure angle in the transmission is acquired with differential geometry and gear meshing theories. The force analysis in the meshing process is performed and the formulas of tangential force and normal force on the gear teeth are derived. A method to calculate elliptical bevel gear’s strength in a successive way is established and the regulation of the tooth surface contacting stress and the root bending stress changing with the angle of driving gear is discussed. Then the position of the weakest tooth is determined and the influence of basic parameters including module,number of teeth and eccentricity ratio on contacting stress and bending stress is analysed. Comparing with traditional calculation for spur bevel gear,the exactness of this successive strength calculation method is verified. 相似文献
In this study, we analyzed the effects of different maize varieties with nitrogen utilization efficiency, fertilizer type, and rate on the ammonia volatilization emission of farmland. Aimed to seek the best matching method to improve grain yield and fertilizer utilization efficiency of summer maize simultaneously.
Materials and methods
In field experiments, we choose two maize varieties with different nitrogen utilization efficiency (Zhengdan958, Z and Lainong14, L) as material. Set four different fertilizer treatments (200 kg N hm?2 inorganic fertilizer (U1), 100 kg N hm?2 inorganic fertilizer (U2), 200 kg N hm?2 organic fertilizer (M1), and 100 kg N hm?2 organic fertilizer (M2) to study their effect on NH3 emission and loss, maize grain yield, and nitrogen accumulation.
Results and discussion
Ammonia volatilization accounted for 8.61–21.68% of applied N. Under the same variety, ammonia volatilization accumulation after fertilization was as follows: U1 > U2 > M1 > M2. Ammonia volatilization rates increased first and then gradually decreased after the fertilization. The ammonia volatilization loss and cumulative loss increased due to increased nitrogen fertilizer application rate. The average nitrogen accumulation and harvest index of 200 kg N hm?2 N treatments were higher than 100 kg N hm?2 N treatments, and the difference between the inorganic fertilizer and organic fertilizer was not significant. In 2016 and 2017, the average yield of Zhengdan958 was 11,758.79 kg hm?2, which was 15.78% higher than that of Lainong14, and the difference between the two fertilizer types was not significant. The average yield of 200 kg N hm?2 N treatment was 11,959.42 kg hm?2, which was 20.13% higher than those of 100 kg N hm?2 N treatment.
Conclusions
By changing the type of fertilizer, replacing chemical fertilizers with organic fertilizer can reduce the loss of ammonia volatilization and promote the synergistic improvement to yield and resource utilization efficiency. Among them, using nitrogen-efficient varieties and using organic fertilizer instead of chemical fertilizer was beneficial to reduce the loss of ammonia volatilization, increase the accumulation of nitrogen, and promote the growth of maize to obtain high yield.
