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Research on Improved Schwarz Arc Model Considering Dynamic Arc Length
Li Jingli,Yuan Hao,Xu Mingming,Tian Fenglan,Wang Zijian,Ren Junyue 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3
Establishing an accurate arc model is significant for simulating arc characteristics and research on arc high impedance fault detection. This paper firstly expounds arc physical properties, and theoretically analyzes the relationship between arc length and arcing voltage. Then, the magnetohydrodynamic model of AC arc is established by COMSOL Multiphysics, and the influence of arc length on electric field intensity, temperature, voltage and current of arc plasma is analyzed. Secondly, based on the influence of arc length on arc, an improved Schwarz arc model considering dynamic arc length is proposed, which not only considers arc time constant and dissipated power as functions of arc conductance, but also introduces arc length. The comparison error of the arcing voltage of the improved Schwarz model with actual measured data is 5%. In addition, the arcing voltage is compared with calculation results of theoretical formula and simulation results of magnetohydrodynamic model, which verifies the validity of improved arc model. Finally, the improved arc model is compared with Mayr model, Schwarz model and cybernetic model from the perspectives of arc voltage and current, and analysis shows that the improved arc model is reasonable in simulating arcing voltage, arc steady-state combustion voltage, and current zero-break characteristics.
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Xianjun Lu,Tingjun Liu,Jiani Zhou,Jia Liu,Zijian Yuan,Lihong Guo 대한치주과학회 2022 Journal of Periodontal & Implant Science Vol.52 No.4
Purpose: To explore differences in the subgingival microbiome according to the presence of periodontitis and/or type 2 diabetes mellitus (T2D), a metagenomic sequencing analysis of the subgingival microbiome was performed. Methods: Twelve participants were divided into 4 groups based on their health conditions (periodontitis, T2D, T2D complicated with periodontitis, and generally healthy). Subgingival plaque was collected for metagenomic sequencing, and gingival crevicular fluids were collected to analyze the concentrations of short-chain fatty acids. Results: The shifts in the subgingival flora from the healthy to periodontitis states were less prominent in T2D subjects than in subjects without T2D. The pentose and glucuronate interconversion, fructose and mannose metabolism, and galactose metabolism pathways were enriched in the periodontitis state, while the phosphotransferase system, lipopolysaccharide (LPS) and peptidoglycan biosynthesis, bacterial secretion system, sulfur metabolism, and glycolysis pathways were enriched in the T2D state. Multiple genes whose expression was upregulated from the red and orange complex bacterial genomes were associated with bacterial biofilm formation and pathogenicity. The concentrations of propionic acid and butyric acid were significantly higher in subjects with periodontitis, with or without T2D, than in healthy subjects. Conclusions: T2D patients are more susceptible to the presence of periodontal pathogens and have a higher risk of developing periodontitis. The pentose and glucuronate interconversion, fructose and mannose metabolism, galactose metabolism, and glycolysis pathways may represent the potential microbial functional association between periodontitis and T2D, and butyric acid may play an important role in the interaction between these 2 diseases. The enrichment of the LPS and peptidoglycan biosynthesis, bacterial secretion system, and sulfur metabolism pathways may cause T2D patients to be more susceptible to periodontitis.
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