Chemical exclusion of predators with permethrin was used to test the effectiveness of the phytoseiid predator Amblyseius limonicus Garman and McGregor and a complex of minor predators in the biological control of tetranychid (Mononychellus spp., Tetranychus spp., and Oligonychus peruvianus McGregor) pests of cassava, Manihot esculenta Crantz. Mononychellus spp. and Tetrunychus spp. populations were significantly higher and predator populations significantly lower in permethrin-treated plots than in control plots. Numbers of 0. peruviunus were not affected by permethrin. Yield of fresh commercial roots and of dry matter was significantly higher in plots with predators than in plots where permethrin was applied every 2 wk for predator exclusion. Yields of neither fresh nor dry matter in control plots were significantly different from yields in plots that had been protected with acaricide, suggesting that predation kept spider mite populations below economically damaging levels. KEY WORDS Arachnida, cassava, permethrin, predator exclusion CASSAVA, Manihot esculenta Crantz, is the most important starchy root crop in the tropics. Although considered to be relatively pest tolerant, recent research has shown that pests that are present throughout the growing cycle (e.g., spider mites)
The analysis of the stray flux for electrical machine condition monitoring is a very modern and active research topic. Thanks to this technique, it is possible to detect several types of failures, as stator and rotor inter-turn faults, broken rotor bars and mechanical faults among others. The main advantages are that is a non-invasive technique applied with low-cost monitoring equipment. The standard practice is to use coreless flux sensors, with which the stray flux of the machine is not perturbed and there are no problems due to saturation or nonlinear behavior of the iron. However, the induced voltage in the coreless coil sensor may be very low and even, in some cases, with similar amplitude than the noise floor. This paper studies the use of iron core stray flux sensors for condition monitoring of electrical machines. The main advantage of iron core flux sensor is that the measured electromotive force is stronger, and in the case of large machines in noisy environments this can be crucial. Two different types of iron core stray flux sensors and a coreless flux sensor are tested. A comparison of the three sensor is presented. Extensive experimental testing with all sensors shows the superiority and greater sensitivity of sensors with core versus the coreless ones.
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