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A new nonlinear photoconductive terahertz radiation source based on photon-activated charge domain quenched mode
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作者 Wei Shi Rujun Liu +1 位作者 Chengang Dong Cheng Ma 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第7期147-150,共4页
We present a high-performance terahertz(THz)radiation source based on the photon-activated charge domain(PACD)quenched mode of GaAs photoconductive antennas(GaAs PCA).The THz radiation characteristics of the GaAs PCA ... We present a high-performance terahertz(THz)radiation source based on the photon-activated charge domain(PACD)quenched mode of GaAs photoconductive antennas(GaAs PCA).The THz radiation characteristics of the GaAs PCA under different operating modes are studied.Compared with the linear mode,the intensity of THz wave radiated by the GaAs PCA can be greatly enhanced due to the avalanche multiplication effect of carriers in the PACD quenched mode.The results show that when the carrier multiplication ratio is 16.92,the peak-to-peak value of THz field radiated in the PACD quenched mode increases by as much as about 4.19 times compared to the maximum values in the linear mode. 展开更多
关键词 photoconductive antenna terahertz time-domain spectroscopy photon-activated charge domain quenched mode
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Health status assessment of axial piston pump under variable speed 被引量:1
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作者 Guo Rui Li Hucheng +3 位作者 Zhao Zhiqian Zhang Rongbing Zhao Jingyi Gao Dianrong 《High Technology Letters》 EI CAS 2020年第3期315-322,共8页
The axial piston pump usually works under variable speed conditions.It is important to evaluate the health status of the axial piston pump under the variable speed condition.Aiming at the characteristic signals obtain... The axial piston pump usually works under variable speed conditions.It is important to evaluate the health status of the axial piston pump under the variable speed condition.Aiming at the characteristic signals obtained under different wear levels of the port plate,a feature signal extraction method under variable speed conditions is proposed.Firstly,the combination of complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN)energy spectrum and fast spectral kurtosis principle is used to accurately extract the intrinsic mode function(IMF)component containing the sensitive information of the degraded feature.Then,the aspect ratio analysis method of the angle domain variational mode decomposition(VMD)is used to process the feature index containing the sensitive information of the degraded feature.In order to evaluate the health status of the axial piston pump under variable speed,the vibration reliability analysis method for axial piston pump based on Weibull proportional failure rate model is proposed.The experimental results show that the proposed method can accurately evaluate the health status of the axial piston pump. 展开更多
关键词 axial piston pump variable speed condition order ratio variational mode decomposition(VMD)in angle domain health status assessment
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Numerical Calculation Methods for Wavemaking Response Induced by Explosion in Harbour
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作者 Li Dejun , Shen Guoguang , Wang Rixin Cheng Hong Professor, Dept. of Ocean and Architecture Engineering, Tianjin University, Tianjin 300072 Lecturer, Dept. of Ocean and Architecture Engineering, Tianjin University, Tianjin 300072 Engineer, Naval Research Centre, P. L. A. of China, Beijing 100055 《China Ocean Engineering》 SCIE EI 1995年第4期355-364,共10页
Using the axial symmetry results of marker and cell (MAC) method as initial value in this paper, two numerical calculating methods are presented for the late wavemaking response induced by explosion in harbour. One of... Using the axial symmetry results of marker and cell (MAC) method as initial value in this paper, two numerical calculating methods are presented for the late wavemaking response induced by explosion in harbour. One of the methods is the superposition method of the vibration mode based on fluid slosh in container. Another one is the joining method of the MAC results with the shallow wave theory calculation in time domain. As a practical example, it is conducted to the numerical calculation about 1000 ton TNT equivalent explosion within touch of water surface. The results show that it can be rationally described with the methods to the wavemaking progress and character. The numerical results are identical with the observed scene on the spot experiment. The methods are simple and applicable in the engineering design. 展开更多
关键词 wavemaking response induced by explosion MAC method superposition method of vibration mode ' joining method in time domain shallow wave theory
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Quenched-Domain Mode of Photo-Activated Charge Domain in Semi-Insulating GaAs Devices
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作者 田立强 施卫 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第10期1913-1916,共4页
The quenched domain mode of the photo-activated charge domain (PACD) in semi-insulating (SI) GaAs photoconductive semiconductor switches (PCSSs) is observed. We find that the quenched domain is induced by the in... The quenched domain mode of the photo-activated charge domain (PACD) in semi-insulating (SI) GaAs photoconductive semiconductor switches (PCSSs) is observed. We find that the quenched domain is induced by the instantaneous electric field across the PCSS being lower than the sustaining electric field of the domain during the transit of the domain. The extinction of the domain before reaching the anode can lead to a current oscillation frequency larger than the transit- time frequency when the bias electric field is lower than the threshold electric field of the nonlinear PCSS. According to the operation circuit and the physical properties of a high-field domain,an equivalent circuit of the quenched domain is presented. The equivalent circuit parameters including capacitance, resonant frequency, and inductance are calculated and measured. Our calculations agree well with the experimental results. This research provides theoretical and experimental criteria for heightening the oscillation frequency and efficiency of PACD devices. 展开更多
关键词 photoconducting switch quenched domain mode equivalent-circuit
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