In this paper, a new spinosad-producing mutant UV-42-13 was obtained by employing rhamnose and sodium propionate resistant selection strategies in series with UV irradiation. Spinosad production of the mutant was 125.3 mg/L, improved 285.5% compared with that of the wild strain (32.5 mg/L).The results of experiment on tolerance of propyl alcohol addition showed that the tolerant ability to precursor was higher. The precursor-resistant ability of the mutant improved through tolerance experiment by adding propyl alcohol, and the spinosad production was greatly increased. The kinetic models for biomass, substrate consumption, and spinosad production of mutant strain and wild strain were studied by conducting batch fermentation in the shaking flask. The result showed that the kinetic models could describe the fermentation process of spinosad producing well.
The aim of local path planning for unmanned surface vehicles (USVs) is to avoid unknown dynamic or static obstacles. However, current relative studies have not fully considered the impact of ocean environmental factors which significantly increase the control difficulty and collision risk of USVs. Therefore, this work studies two ocean environmental factors, namely, wave and current, given that they both have a significant impact on USVs. Furthermore, we redesign a kinematic model of an USV and the evaluation function of a classical and practical local path planning method based on the dynamic window approach (DWA). As shown by the results of the simulations, the path length was impacted mainly by the intensity of the environmental load and slightly by the direction of the environmental load, but the navigation time was significantly influenced by both. Taking the situation in still water as a benchmark in terms of the intensity and direction of the environmental factors, the maximum change rates of the path length were 8.6% and 0.6%, respectively, but the maximum change rates of the navigating time were 17.9% and 25.6%, separately. In addition, the average calculation time of each cycle was only 0.0418 s, and the longest time did not exceed the simulation time corresponding to a single cycle of 0.1 s. This method has proven to be a good candidate for real-time local path planning of USVs since it systematically considers the impact of waves and currents on the navigation of USVs, and thus ensures that USVs can adjust to the planned path in time and avoid obstacles when navigating in the real ocean environment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.