In order to explore the spatial pesticide spraying deposition distribution, the downwash flow field characteristics for unmanned aerial vehicle (UAV) pesticide application with accurate flight height and velocity and the relationship of these two aspects, a novel measurement method was proposed in this paper. A model '3WQF80-10' single-rotor diesel UAV was tested using this method in wheat field and the effects of flight direction, flight parameters and crosswind on the distribution of spatial spraying deposition quality balance (SSDQB) and the downwash flow field distribution were researched. A cuboid aluminum sampling frame of spatial spraying deposition quality balance (SFSSDQB) with monofilament wires was made for collecting the droplets in four directions, and a set of multi-channel micro-meteorology measurement system (MMMS) was applied for measuring the downwash wind speed in three directions. Besides, BeiDou Navigation Satellite System (BNSS) was used for controlling and recording the working height, velocity and track of this model of single-rotor UAV. The results showed the distribution of the spatial spray deposition and the downwash flow field of UAV could be measured effectively at exact flight height and velocity via this method. When the average wind speed was 0.9 m/s, the average temperature was 31.5°C and the average relative humidity was 34.1%, and the average distribution ratios of spraying deposition for model '3WQF80-10' UAV on the upwind part, the top part, the downwind part and the bottom part were 4.4%, 2.3%, 50.4% and 43.7%, respectively. The flight directions of forward and backward had an impact on droplet deposition distribution and the working effect of flying backwards, with 60% of deposition ratio of the bottom part of the SFSSDQB, was better than flying forward. There was a linear negative correlation between the coefficient of variation (CV) of the bottom part and the flight height and the coefficient of determination was 0.9178, which means that the deposition distribution becomes more uniform with the increase of height. Additionally, there was a linear positive correlation between weighted mean deposition rate and crosswind speed and the coefficient of determination was 0.9684, which shows the deposition distribution gets more concentrated towards the downwind part with the rise of crosswind speed. Therefore, according to the results of tests of downwash airflow speed, it is shown that regardless of the flight direction and height and the crosswind, all these factors influence the droplet deposition distribution via weakening the intensity of the downwash airflow field in the direction perpendicular to the ground. The results can provide valuable information for the research of UAV pesticide application techniques and the establishment of the standard of spraying deposition and drift tests of UAV in crop field.

This paper combines experimental data with simple mathematical models to investigate the influence of spray formulation type and leaf character (wettability) on shatter, bounce and adhesion of droplets impacting with cotton, rice and wheat leaves. Impaction criteria that allow for different angles of the leaf surface and the droplet impact trajectory are presented; their predictions are based on whether combinations of droplet size and velocity lie above or below bounce and shatter boundaries. In the experimental component, real leaves are used, with all their inherent natural variability. Further, commercial agricultural spray nozzles are employed, resulting in a range of droplet characteristics. Given this natural variability, there is broad agreement between the data and predictions. As predicted, the shatter of droplets was found to increase as droplet size and velocity increased, and the surface became harder to wet. Bouncing of droplets occurred most frequently on hard to wet surfaces with high surface tension mixtures. On the other hand, a number of small droplets with low impact velocity were observed to bounce when predicted to lie well within the adhering regime. We believe this discrepancy between the predic-G.J. Dorr (joint first author), tions and experimental data could be due to air layer effects that were not taken into account in the current bounce equations. Other discrepancies between experiment and theory are thought to be due to the current assumption of a dry impact surface, whereas, in practice, the leaf surfaces became increasingly covered with fluid throughout the spray test runs. arXiv:1506.04258v1 [physics.flu-dyn]

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Chitinases play a vital part in the molting phase of insect pests. Inhibiting their activities by the use of drug-like small chemical molecules is thought to be an efficient strategy in pesticide design and development. On the basis of the crystal structure of OfChtI, a chitinase indispensable for the molting of the insect pest Ostrinia furnacalis (Asian corn borer), here we report a chemical fragment and five variant compounds as inhibitors of OfChtI obtained from a library of over 200 000 chemicals by a structure-based-virtual-screening approach. The compounds were synthesized with high atom economy and tested for their OfChtI-inhibitory activities in a bioassay. Compound 3 showed preferential inhibitory activity with a K value of 1.5 μΜ against OfChtI. Analysis of the structure-activity relationships of the compounds provided insight into their interactions with the enzyme active site, which may inform future work in improving the potencies of their inhibitory activities.

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