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To explore a wireless sensor network (WSN) system and node deployment in persimmon orchards, this paper focused on the wireless network signal transmission under the 2.4 GHz radio channel in the persimmon orchard when it was in the germination stage, young leaves stage, and flowering stage, three growth periods. A row of persimmon tress in the growth period was selected. By adjusting the height and distance of the node and father node, the distance from three different heights from 0.80 meters at the bottom of the tree and 1.80m at the most luxuriant foliage location to 2.80 meters at the top of the canopy wee measured. Persimmon trees were measured for each growth period resulting in 72 groups of data. Results showed the LQI value with the change of the distance, the sine curve type attenuation trend, and the difference was obvious in the three growth periods. The radio signal attenuation data measured the worst minimal in the flowering stage, because the branches and leaves of signal reflection, refraction, and absorption was the most serious in this period. It is showed that the best effective transmission distance of each column of trees was 38m when child nodes and father nodes are on the top of the canopy (2.80 m) in germination, while in the young leaves stage, the height of the child nodes and father nodes are located in the top of the canopy, when the node is the best place to pitch 32m. In the flowering stage, child nodes and father nodes are on the top of the canopy, and the best distance is 26m. In the case when plant height is not very high, when the device is placed on top of the node, the wireless sensor networks optimal signal transmission distance changes as the degree of lush foliage plants is smaller and smaller. During the experiment, because the orchard in the wild environment was susceptible to the wind, the corresponding external factors, such as the difference of the instantaneous value, sometimes the LQI was big. Based on two data sets, curve fittings were established in the 2.4GHz channel signal attenuation model, which cubic polynomial model maximum correlation was coefficient R squared for an optimal model. A model of R value was the biggest of all. In the germination stage, R squared was 0.754-0.958; in the young leaves stage it was 0.805-0.979; and in the flowering stage it was 0.758-0.991. Wireless sensor network research on orchard signal transmission loss provided the technical basis for the deployment of wireless sensor network nodes in orchards. [ABSTRACT FROM AUTHOR]

The chief function of sub-nozzle of impact sprinkler is to increase the near precipitation depth, thereby improving the uniformity of sprinkler irrigation. In this study, flow field simulation combined with experimental validation method was applied to optimize the key structural parameters (elevation angle and position) of impact sprinkler. Nine kinds of elevation angles and positions of sub-nozzle combinations were designed with the established three-dimensional structures of the impact sprinkler by Pro/E software. The three-dimensional inner flow channel model of impact sprinkler with nine kinds of sub-nozzle structure was established. The inner flow channel simulations of all kinds of impact sprinkler were performed by FLUENT of Computational Fluid Dynamics (CFD) software. Considering structural feature, the precision requirement, the procession quality, and the cost of product, the SLA RPT (Stereo lithography Apparatus Rapid Prototyping Technology) was selected to prototype the impact sprinkler with nine kinds of sub-nozzle. The nine kinds of models were processed into samples for experimental verification. Under the rectangular combinations, four interpolation methods (distance interpolation method, linear interpolation method, cubic interpolation method and cubic spline interpolation method) were used to calculate the Christiansen uniformity coefficient and nine kinds of water pressure distribution models were established by Sprinkler 3D software in two-dimensional interpolation method. The result showed that the impact sprinklers with sixth sub-nozzle (position parameter of 19.8 mm, the elevation angle parameter of 18°) performed more reliable. The study about sub-nozzle of impact sprinkler's structural parameters improved the nozzle near water distribution effectively. Its flow rate of simulation was biggest. The yield of water distribution in 2-12 m could maintain good uniformity. And the sprinkler range of the sixth sub-nozzle was more than 14 m, better than before and increased by more than 2 m. The sprinkler irrigation uniformity was calculated with the four different interpolation methods and results were increased obviously. Under the pressure of 250 and 300 kPa (especially the pressure of 300 kPa), the Christiansen uniformity coefficient both was more than 80%, which was an increase of 4% and 5% above than before. With the increase of the pressure, Christiansen uniformity coefficient was still consistent generally. The structural parameters of sub-nozzle (position parameter of 19.8 mm and the elevation angle parameter of 18°) of impact sprinklers were more reasonable. This study provides valuable information for structural design of sub-nozzle, impact sprinkler and sprinkler system optimization. [ABSTRACT FROM AUTHOR]