In order to effectively imitate the dynamic operation characteristics of the HVDC （high voltage direct current） power transmission system at a real ±500kV HVDC transmission project, the electromechanical-electr...In order to effectively imitate the dynamic operation characteristics of the HVDC （high voltage direct current） power transmission system at a real ±500kV HVDC transmission project, the electromechanical-electromagnetic transient hybrid simulation was carried out based on advanced digital power system simulator （ADPSS）. In the simulation analysis, the built hybrid model＇s dynamic response outputs under three different fault conditions are considered, and by comparing with the selected fault recording waveforms, the validities of the simulation waveforms are estimated qualitatively. It can be ascertained that the hybrid simulation model has the ability to describe the HVDC system＇s dynamic change trends well under some special fault conditions.展开更多
Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coo...Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.展开更多
Full-length RNA4 of beet necrotic yellow vein virus (BNYVV) and its mutants, including a frame-shift and deletions within the coding region, were inserted into a transcription plasmid. Transcripts derived from these p...Full-length RNA4 of beet necrotic yellow vein virus (BNYVV) and its mutants, including a frame-shift and deletions within the coding region, were inserted into a transcription plasmid. Transcripts derived from these plasmids and RNAs extracted from a BNYVV isolate containing only RNAs 1, 2 and 3 were coinoculated to Tetragona expansa. Then these recombinant isolates were inoculated to sugar beet plants grown in a sand culture system containing Po-lymyxa betae that had been freed of virus particles to test efficiency of BNYVV transmission. The result showed that the efficiency of BNYVV transmission among the plants by Polymyxa betae was highly decreased by different deletions in the coding region of RNA4, but not affected by the frame-shift mutant with four nucleotides insertion. The observations suggest that at least some of the RNA4 sequence encompassing the deleted region of 580 nucleotide acids (525 -1105 nt) are necessary for high efficient transmission of the virus by the fungus.展开更多
基金supported by the General Program of Chinese Postdoctoral Science Foundation under Grant No.2012M511595
文摘In order to effectively imitate the dynamic operation characteristics of the HVDC （high voltage direct current） power transmission system at a real ±500kV HVDC transmission project, the electromechanical-electromagnetic transient hybrid simulation was carried out based on advanced digital power system simulator （ADPSS）. In the simulation analysis, the built hybrid model＇s dynamic response outputs under three different fault conditions are considered, and by comparing with the selected fault recording waveforms, the validities of the simulation waveforms are estimated qualitatively. It can be ascertained that the hybrid simulation model has the ability to describe the HVDC system＇s dynamic change trends well under some special fault conditions.
文摘Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
基金This work was partially supported by the National Natural Science Foundation of China (Grant No. 39670035)the State "863" High-Tech Program Specifical Fund for Young Scientists.
文摘Full-length RNA4 of beet necrotic yellow vein virus (BNYVV) and its mutants, including a frame-shift and deletions within the coding region, were inserted into a transcription plasmid. Transcripts derived from these plasmids and RNAs extracted from a BNYVV isolate containing only RNAs 1, 2 and 3 were coinoculated to Tetragona expansa. Then these recombinant isolates were inoculated to sugar beet plants grown in a sand culture system containing Po-lymyxa betae that had been freed of virus particles to test efficiency of BNYVV transmission. The result showed that the efficiency of BNYVV transmission among the plants by Polymyxa betae was highly decreased by different deletions in the coding region of RNA4, but not affected by the frame-shift mutant with four nucleotides insertion. The observations suggest that at least some of the RNA4 sequence encompassing the deleted region of 580 nucleotide acids (525 -1105 nt) are necessary for high efficient transmission of the virus by the fungus.
