Introduction: We analyzed the clinical characteristics of COVID-19 fecal/perianal swab nucleic acid-positive patients in our hospital and evaluated the effect of SARS-CoV-2 on the gastrointestinal tract. Methodology: Ninety-seven patients in the Fifth Affiliated Hospital of Sun Yat-sen University from January 17, 2020 to March 2, 2020 with fecal/perianal swab samples were selected as subjects and the results of real-time fluorescence reverse transcriptase-PCR SARS-CoV-2 nucleic acid detection of fecal/perianal swabs were used to divide subjects into positive and negative groups. Results: Fecal/perianal swabs of 53.61% (52/97) patients were positive including 31 males (59.62%) and 21 females (40.38%). The negative group had more females than males (P = 0.001). The distribution of case classification based on the most severe condition observed after admission was different between groups: five (5.15%) critical type patients were all from the positive group (P = 0.029). There was no statistical difference in clinical manifestations between the groups. In the positive group, the mean nucleic acid-negative conversion time was 14.13 ± 8.61 days, which was significantly later than the negative group (6.98 ± 5.16 days; P < 0.001). In the positive group, 92% (48/52) had nucleic acid-negative conversion with a mean nucleic acid-negative conversion time of 22.58 ± 10.30 days. Among them, 41 (78.85%) cases were delayed compared with pharynx/nasal swab nucleic acid-negative conversion time. Conclusions: The positive rate of fecal/perianal swab nucleic acid in male patients was higher than that in female patients. Fecal/perianal swab nucleic acid positive may be an indicator of critical conditions in those with COVID-19.

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Based on low temperature superconducting (LTS) & high temperature superconducting (HTS) material classification, the superconducting generators can be divided into LTS generators and HTS generators. The research status and characteristics of superconducting generators are summarized; and several topological structures of superconducting generators are introduced. Compared and studied traditional rotating machine with superconducting rotating machine, pointing out the present superconducting generators bottleneck problems. Finally, the prospects of the development of superconducting generators are described.

In order to deal with the difficulty of magnetic field adjustment in permanent magnet synchronous generators (PMSG), this paper proposed a novel paratactic structure hybrid excitation synchronous generators (HESG) and presented the basic configuration and its principle. Then, it analyzed three combination methodsof PMSG and the electro-excitation synchronous generators (EESG) in HESG,and also presented calculation way of field current in HESG. Finally, the experimental results proved the correctness of those analyses.

In order to deal with the difficulty of magnetic field adjustment in permanent magnet synchronous machines, this paper proposed a novel paratactic structure hybrid excitation synchronous generator (HESG) and presented the basic configuration and its principle. Then, with the analysis of armature reactions, it introduced the detailed working performances of permanent magnet synchronous generator (PMSG) and the electric excitation synchronous generator (EESG) in HESGunder different field current conditions. We can classify the operating modes of HESGinto three categories: double-generation mode, single-generation mode and generation-motor mode whose boundaries were deduced. Finally, the experimental results proved the correctness of those analyses.