The electromagnetic suspension high-speed maglev train system uses long-stator linear synchronous motors (LLSMs) as levitation and traction mechanisms. In this paper, the modeling and simulation of the traction power supply system for the maglev train are performed. The simulation models include transformers, converters, variable-length cables and LLSMs of both two sides and two ends; meanwhile, the corresponding control and segmented power supply strategies, including the two-step method and three-step method, are implemented. Based on the system model, the operational performance of the high-speed maglev power supply control system is verified, and the fault performances under open circuit and short circuit are also analyzed. The whole simulation modeling and results have important reference significance for the research of high-speed maglev technology.
A simple, rapid, and environmentally friendly sample preparation method for pyrethroids determination in cereals using cyclodextrin-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplets coupled with high-performance liquid chromatography was established. The cereal samples were extracted with acetonitrile, cleaned up, and concentrated by green extractant menthol via γ-cyclodextrin assisted extraction process. The extractant menthol dispersed as fine droplets in the cyclodextrin solution and then solidified at room temperature for efficient extraction and convenient collection. The optimized method provided good linearity in the range of 0.01–10 mg kg−1 with limits of detection of 3.5–9.5 μg kg−1. The fortified recoveries of three pyrethroids (i.e., lambda-cyhalothrin, deltamethrin, and bifenthrin) in four cereals (i.e., rice, wheat, maize, and millet) at three levels were in the range of 77.6–101.6% with relative standard deviations of 0.6–6.6%. Overall, the proposed method can be successfully applied for the determination of pyrethroids in cereals.
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