针对直驱风力发电系统中变流器IGBT存在过电压脉冲的问题,基于IGBT的物理模型及C型、钳位二极管、RC型和RCD型四种过电压保护电路提出了一种新型CR-CD(Capacitor resistor and capacitor diode)过电压保护电路。首先,分析了CR-CD过电压...针对直驱风力发电系统中变流器IGBT存在过电压脉冲的问题,基于IGBT的物理模型及C型、钳位二极管、RC型和RCD型四种过电压保护电路提出了一种新型CR-CD(Capacitor resistor and capacitor diode)过电压保护电路。首先,分析了CR-CD过电压保护电路的工作原理,论证了CR-CD过电压保护电路抑制过电压脉冲的优良性能。其次,详细设计了过电压保护电路的参数。最后,基于Matlab/Simulink平台搭建了CR-CD型过电压保护电路仿真模型,分别在恒定和变化负载电感两种工况下进行仿真对比分析。结果表明:CR-CD过电压保护电路不仅可以有效地抑制过电压脉冲,还能起到避免因电容造成的过电压脉冲衰减延迟以及缩短IGBT关断时间的作用。展开更多
Complement receptor 2 （CR2/CD21） is predominantly expressed on the surface of mature B cells where it forms part of a coreceptor complex that functions, in part, to modulate B-cell receptor signal strength. CR2/CD21...Complement receptor 2 （CR2/CD21） is predominantly expressed on the surface of mature B cells where it forms part of a coreceptor complex that functions, in part, to modulate B-cell receptor signal strength. CR2/CD21 expression is tightly regulated throughout B-cell development such that CR2/CD21 cannot be detected on pre-B or terminally differentiated plasma cells. CR2/CD21 expression is upregulated at B-cell maturation and can be induced by IL-4 and CD40 signaling pathways. We have previously characterized elements in the proximal promoter and first intron of CR2/CD21 that are involved in regulating basal and tissue-specific expression. We now extend these analyses to the CR2/CD21 core promoter. We show that in mature B cells, CR2/~D21 transcription proceeds from a focused TSS regulated by a non-consensus TATA box, an initiator element and a downstream promoter element. Furthermore, occupancy of the general transcriptional machinery in pre-B versus mature B-cell lines correlate with CR2/CD21 expression level and indicate that promoter accessibility must switch from inactive to active during the transitional B-cell window.展开更多
文摘针对直驱风力发电系统中变流器IGBT存在过电压脉冲的问题,基于IGBT的物理模型及C型、钳位二极管、RC型和RCD型四种过电压保护电路提出了一种新型CR-CD(Capacitor resistor and capacitor diode)过电压保护电路。首先,分析了CR-CD过电压保护电路的工作原理,论证了CR-CD过电压保护电路抑制过电压脉冲的优良性能。其次,详细设计了过电压保护电路的参数。最后,基于Matlab/Simulink平台搭建了CR-CD型过电压保护电路仿真模型,分别在恒定和变化负载电感两种工况下进行仿真对比分析。结果表明:CR-CD过电压保护电路不仅可以有效地抑制过电压脉冲,还能起到避免因电容造成的过电压脉冲衰减延迟以及缩短IGBT关断时间的作用。
文摘Complement receptor 2 （CR2/CD21） is predominantly expressed on the surface of mature B cells where it forms part of a coreceptor complex that functions, in part, to modulate B-cell receptor signal strength. CR2/CD21 expression is tightly regulated throughout B-cell development such that CR2/CD21 cannot be detected on pre-B or terminally differentiated plasma cells. CR2/CD21 expression is upregulated at B-cell maturation and can be induced by IL-4 and CD40 signaling pathways. We have previously characterized elements in the proximal promoter and first intron of CR2/CD21 that are involved in regulating basal and tissue-specific expression. We now extend these analyses to the CR2/CD21 core promoter. We show that in mature B cells, CR2/~D21 transcription proceeds from a focused TSS regulated by a non-consensus TATA box, an initiator element and a downstream promoter element. Furthermore, occupancy of the general transcriptional machinery in pre-B versus mature B-cell lines correlate with CR2/CD21 expression level and indicate that promoter accessibility must switch from inactive to active during the transitional B-cell window.
