CAS:59483-84-0，BIS(PENTAFLUOROPHENYL)CARBONATE，DPFPC

Unlike the conventional boost-derived power-factor-correction (PFC) converter, the cell series-parallel (MCSP) converter can step-up/step-down the output voltage. Its modular concept has a flexibility to select the voltage rating of switches depending on the number of cells. Based on its high degree-of-freedom (DOF) in combination of switching states, this article proposes an optimal switching method that can suppress the amplitudes of switch currents while improving converter efficiency by synthesizing pentagonal inductor current waveform in critical conduction mode (CRM) control. In addition, a total harmonic distortion of input current (iTHD) is improved with variable additional on-time control. Thanks to an inherent capacitor voltage balancing feature of the MCSP converter, it does not require additional balancing control. The feasibility of the proposed control is verified by experiments in the 300 W prototype.

This article proposes new fully soft-switched bridgeless buck-boost power-factor-correction converters using single-magnetic core with capability of realizing positive or negative output voltages. Full zero-voltage switching operation is provided for the main switches independent of the load and grid voltage variations. Also, the proposed converters have common ground and single ended output, which increase power density and alleviates common mode noise. The proposed converters operate under discontinuous conduction mode to shape the input current inherently. A 120 W, 100 kHz laboratory prototype with negative output voltage is implemented to verify the theoretical analysis and the effectiveness of the proposed topologies. The results demonstrate efficiency of 96.2% and total harmonic distortion of 4% at full-load condition.

A method of quantification of perfluorinated compounds (PFCs) from atmospheric particulate matter (APM) is described. A single step pretreatment method, selective pressurized liquid extraction (SPLE), was developed to reduce the high matrix background and avoid contamination from commonly used multiple sample pretreatment steps. An effective sorbent was selected to purify the PFCs during SPLE, followed by liquid chromatography-tandem mass spectrometry (LC–MS/MS), for quantification of PFCs. Conditions affecting the SPLE efficiency, including temperature, static extraction time, and number of extraction cycles used, were studied. The optimum conditions were found to be 120°C, 10 min, and 3 cycles, respectively. LC-MS/MS method was developed to obtain the optimal sensitivity specific to PFCs. The method detection limits (MDLs) were 0.006 to 0.48 ng/g for the PFCs studied and the linear response range was from 0.1 to 100 ng/g. To ensure accurate values were obtained, each step of the experiment was evaluated and controlled to prevent contamination. The optimized method was tested by performing spiking experiments in natural particulate matter matrices and good rates of recovery and reproducibility were obtained for all target compounds. Finally, the method was successfully used to measure 16 PFCs in the APM samples collected in Beijing over five years from 2015 to 2019. It is observed that some PFCs follow the trend of total PFC changes, and can be attributed to the environment influencing events and policy enforcement, while others don't seem to change as much with time of the year or from year to year.