High-frequency harmonic resonance has been a frequently encountered issue in railway traction power supply system (TPSS) since high-speed trains that are equipped with ac-dc-ac traction drive system were serviced in China High-Speed Railway (HSR) lines. This high-frequency harmonic resonance is excited when the frequency of harmonic components introduced by the grid-side traction ac-dc converter in trains matches the inherent resonance frequency of TPSS. Traditional solutions for this HSR high-frequency resonance focus on providing damping to the TPSS. In this work, with a focus on avoiding the resonance excitation, a solution from the trains' perspective through adoption of single-phase grid-side pulse-width-modulated (PWM) converter with LCL filter in high-speed trains is proposed. Compared with the traditional traction system topology with L-type filter, the total inductance value of LCL filter is designed to be the same with that of L-type filter and there is only an additional small capacitor adopted in the proposed solution. Therefore the design in this work meets the space and weight requirements of the traction converter system. In this work, an all-parallel 27.5-kV 50-Hz autotransformer (AT)-fed power-supply system and the proposed grid-side LCL filter based converters are modeled and simulated in real-time hardware in loop (HIL) experimental platform. The results show that the proposed solution can effectively suppress the high-frequency resonance of TPSS.

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Many infertile men are the victims of spermatogenesis disorder. However, conventional clinical test could not provide efficient information on the causes of spermatogenesis disorder and guide the doctor how to treat it. More effective diagnosis and treating methods could be developed if the key genes that regulate spermatogenesis were determined. Many works have been done on animal models, while there are few works on human beings due to the limited sample resources. In current work, testis tissues were obtained from 27 patients with obstructive azoospermia via surgery. The combination of Fluorescence Activated Cell Sorting and Magnetic Activated Cell Sorting was chosen as the efficient method to sort typical germ cells during spermatogenesis. RNA Sequencing was carried out to screen the change of transcriptomic profile of the germ cells during spermatogenesis. Differential expressed genes were clustered according to their expression patterns. Gene Ontology annotation, pathway analysis, and Gene Set Enrichment Analysis were carried out on genes with specific expression patterns and the potential key genes such as HOXs, JUN, SP1, and TCF3 which were involved in the regulation of spermatogenesis, with the potential value serve as molecular tools for clinical purpose, were predicted.

Author contributions: Wen-Ming Chu conceived and directed the project and performed a large body of experiments.

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