A time-of-arrival(TOA) system based on GPS technology for locating VHF radiation sources from lightning has been developed and used in observation sites in the northern Shandong Province,China.The 3D images of the lig...A time-of-arrival(TOA) system based on GPS technology for locating VHF radiation sources from lightning has been developed and used in observation sites in the northern Shandong Province,China.The 3D images of the lightning progression have been obtained successfully for the first time in China.The 3D-channel evolutions of typical negative CG,positive CG and IC lightning flashes have been discussed together with the data of fast electric field change.It was found that significant differences existed between the negative and positive CG lightning flashes in terms of the initiation and propagation of the radiation sources.The preliminary breakdown of a negative CG lightning flash propagated at a speed about 5.2×104 m/s.The stepped leader of negative CG lightning flashes was trigged by negative initial breakdown.Thereafter,it propagated downward at a speed of 1.3×105 m/s.The initial process of the positive CG lightning flashes was also a propagation process of negative streamer.These streamers propagated dominantly horizontally in the positive charge region and accumulated positive charges at the origin of the lightning,and as a consequence,initiated downward positive streamers.A new type of lightning discharge that was triggered by a narrow bipolar pulse(NBP) is discussed in this study.The NBP was originated at altitude of about 10.5 km in the upper positive charge region.As a distinct difference from normal IC flash,its channels extended horizontally all around and produced a lot of radiation sources.The source power of the NBP could approach 16.7 kW,which is much greater than that of normal lightning discharge ranging between 100 mW and 500 W.The 3D propagation of this new type of lightning discharge was observed and obtained for the first time in China.The possible initiation mechanism of this new type of light-ning is discussed here.展开更多
In order to increase the usefulness of pulsed current source in engineering practice, research and study was carried out on how to increase the pulse current amplitude, reduce the rise /fall time of output pulse and M...In order to increase the usefulness of pulsed current source in engineering practice, research and study was carried out on how to increase the pulse current amplitude, reduce the rise /fall time of output pulse and MOSFET switching losses, etc. Through the analysis of the pulsed current source works theory and the mathematical derivation of the circuit model, the deduction and calculation of the pulse edge compression control methods, and improve the overall circuit structure and optimize the manufacturing process according to the theory. The following indicators was realized： the output pulse current amplitude can be up to 100 A, the shortest pulse rise / fall time was 18.8 ns and 16.1 ns respectively when the maximum amplitude output, the pulse width could be narrowest to 40 ns, repetition frequency could achieve 10 Hz to 10 k Hz, MOSFET switching losses decreased by 30.9 %. This pulsed current source can be used, not only as the power supply for the ordinary high speed narrow pulse width laser diode, but also as an ideal drive power for the high energy, narrow width pulse laser diode.展开更多
基金supported by National Natural Science Foundation of China (Grant No.40775004)Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW-206-2)the R & D Special Fund for Public Welfare Industry (meteorology) (Grant No.GYHY2007622)
文摘A time-of-arrival(TOA) system based on GPS technology for locating VHF radiation sources from lightning has been developed and used in observation sites in the northern Shandong Province,China.The 3D images of the lightning progression have been obtained successfully for the first time in China.The 3D-channel evolutions of typical negative CG,positive CG and IC lightning flashes have been discussed together with the data of fast electric field change.It was found that significant differences existed between the negative and positive CG lightning flashes in terms of the initiation and propagation of the radiation sources.The preliminary breakdown of a negative CG lightning flash propagated at a speed about 5.2×104 m/s.The stepped leader of negative CG lightning flashes was trigged by negative initial breakdown.Thereafter,it propagated downward at a speed of 1.3×105 m/s.The initial process of the positive CG lightning flashes was also a propagation process of negative streamer.These streamers propagated dominantly horizontally in the positive charge region and accumulated positive charges at the origin of the lightning,and as a consequence,initiated downward positive streamers.A new type of lightning discharge that was triggered by a narrow bipolar pulse(NBP) is discussed in this study.The NBP was originated at altitude of about 10.5 km in the upper positive charge region.As a distinct difference from normal IC flash,its channels extended horizontally all around and produced a lot of radiation sources.The source power of the NBP could approach 16.7 kW,which is much greater than that of normal lightning discharge ranging between 100 mW and 500 W.The 3D propagation of this new type of lightning discharge was observed and obtained for the first time in China.The possible initiation mechanism of this new type of light-ning is discussed here.
基金supported by the Changchun Science and Technology Project (13KG28)the Jilin Province Science and Technology Development Plan (20120320)
文摘In order to increase the usefulness of pulsed current source in engineering practice, research and study was carried out on how to increase the pulse current amplitude, reduce the rise /fall time of output pulse and MOSFET switching losses, etc. Through the analysis of the pulsed current source works theory and the mathematical derivation of the circuit model, the deduction and calculation of the pulse edge compression control methods, and improve the overall circuit structure and optimize the manufacturing process according to the theory. The following indicators was realized： the output pulse current amplitude can be up to 100 A, the shortest pulse rise / fall time was 18.8 ns and 16.1 ns respectively when the maximum amplitude output, the pulse width could be narrowest to 40 ns, repetition frequency could achieve 10 Hz to 10 k Hz, MOSFET switching losses decreased by 30.9 %. This pulsed current source can be used, not only as the power supply for the ordinary high speed narrow pulse width laser diode, but also as an ideal drive power for the high energy, narrow width pulse laser diode.
