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Jia Qi,Gangui Yan,Liu Kan,Hu Wenbo,Wang Junxi 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.2
Subsynchronous oscillations (SSOs) induced during the generation of wind power constitute an important problem that aff ects the safety and the stability of power systems. It is useful to study the impact of wind turbines on the damping of the SSOs of a synchronous generator (SG). On the one hand, the relevant studies have been based mainly on eigenvalue analysis, which is insuffi cient, and on the other, an examination of the general mechanism of the SSO is still lacking. Based on the net electrical damping analysis method, this paper examines the dynamic interaction between the SG and doubly fed induction generator-based wind turbines (DFIGs). The self-stabilizing damping coeffi cient and the mutually stabilizing damping coeffi cient are proposed from the perspective of the SG, and the eff ects of diff erent numbers and current loop control parameters of the DFIGs on torsional modes of the SG are analyzed using diff erent grid structures. A time-domain simulation model of DFIGs connected to a power grid is built in EMTDC/PSCAD to verify the correctness of the theoretical analysis.
Electronic and optical properties of graphane, silicane, MoS2 homo-bilayers and hetero-bilayers
Jia-Qi Hu,Lin-Han Xu,Shun-Qing Wu,Zi-Zhong Zhu 한국물리학회 2019 Current Applied Physics Vol.19 No.11
The electronic and optical properties of graphane, silicane and MoS2 bilayers, as well as the graphane/MoS2 and silicane/MoS2 hetero-bilayers, are calculated by the first-principles method. The interlayer interactions of all the bilayer systems are shown to be mainly van der Waals. Both the graphane/MoS2 and silicane/MoS2 heterobilayers belong to the type-II heterostructure, which can be utilized in photo-voltaic devices due to the efficient spatial separation of electrons and holes. For optical properties, the distinctions for the imaginary parts of the dielectric function 2 ( ) between the monolayer and bilayer systems for both the graphane and silicane are more evident in electric vector E||z. However, the differences between 2 ( ) of the monolayer and bilayer MoS2 materials are more significant in E||x. Broader light absorption ranges of the hetero-bilayers are reached, which can also improve the charge separation of the electron-hole pairs.
Jia-Qi Chu,박창식,유명조,전무형,김명철 한국임상수의학회 2008 한국임상수의학회지 Vol.25 No.3
To investigate the genotypic diversity of the porcine reproductive and respiratory syndrome viruses (PRRSV) in Korea, we examined 92 clinical samples from three provinces by RT-PCR and a nested PCR, and the complete open-reading frame 7 (ORF 7) sequences of 15 samples selected from 72 PCR-positive specimens were analyzed. When we compared nucleotide (amino acid) sequences of 80 isolates from Korea and overseas countries, the sequences of 7 samples belonged to North American (NA)-genotype, and those of 8 samples, to European (EU)-genotype. The nucleotide (amino acid) identities between two genotypes were 63.7% (59.8%) to 65.1% (63.1%). When compared with NA prototype VR-2332, the 7 strains of NA-genotype shared 89.8% (93.6%) to 91.2% (96.0%) identity of nucleotide (amino acid) sequence. The 8 strains of EU-type shared 93.6% (92.3%) to 94.3% (93.8%) identity of nucleotide (amino acid) sequence as compared to EU prototype Lelystad. In phylogenetic tree analysis by neighborjoining method, all of the 8 EU-type strains were clustered into group 4 distinct from EU-prototype Lelystad (group 1). In NA-genotype, 24 domestic isolates reported previously and the 7 strains of NA-type determined in this study were clustered into group 1, while US prototype VR 2332 was classified into different group (group 2). These results suggest that emergence of EU-genotype and the dual-infection of NA- and EU-genotypes may be prevalent in the pig farms in Korea. The high degree of genetic diversity of field PRRSVs should be taken into consideration for control and preventive measures.