It is critical for cerebral vascular disease diagnosis through Doppler to detect the maximum and the minimum of the carotid blood flow speed accurately. A kind of Duffing system under an external periodic power with d...It is critical for cerebral vascular disease diagnosis through Doppler to detect the maximum and the minimum of the carotid blood flow speed accurately. A kind of Duffing system under an external periodic power with dump is introduced in the letter, numerical analysis is carried out by four-order Runge-Kutta method. An oscillator array is designed according to the frequency of the ultrasonic wave. When the external signals are inputted, computational algorithm is used to scan the array in turn and analyze the result, and the frequency can be determined. Based on the methods above, detecting the carotid blood flow speed accurately is realized. The Signal-to-Noise Ratio (SNR) of-20.23dB is obtained by the result of experiments. In conclusion, the SNR has been improved and the precision of the measured bloodstream speed has been increased, which can be 0.069% to 0.13%.展开更多
An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 we...An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 were obtained on this device, which enable it to be used for neutron detection in multi-radiation field. Moreover, the neutron sensitivity of this detector was characterized theoretically and experimentally. And for fast and ultra-fast neutron, the detection sensitivity is in the magnitude of 10^-17 to 10^-16 C cm^2/n with good stability and negligible pump effect. All these results indicate that the as-prepared sensor to be ideal for fast and ultra-fast neutron monitoring, and it may pave the way to build neutron detector with low cost and large sensitive area with diamond.展开更多
基金Supported by the National Natural Science Foundation of China (No.60102002)the Huoyingdong Education Foundation (No.81057)the Doctoral Foundation of Hebei Province of China(No.B2004522).
文摘It is critical for cerebral vascular disease diagnosis through Doppler to detect the maximum and the minimum of the carotid blood flow speed accurately. A kind of Duffing system under an external periodic power with dump is introduced in the letter, numerical analysis is carried out by four-order Runge-Kutta method. An oscillator array is designed according to the frequency of the ultrasonic wave. When the external signals are inputted, computational algorithm is used to scan the array in turn and analyze the result, and the frequency can be determined. Based on the methods above, detecting the carotid blood flow speed accurately is realized. The Signal-to-Noise Ratio (SNR) of-20.23dB is obtained by the result of experiments. In conclusion, the SNR has been improved and the precision of the measured bloodstream speed has been increased, which can be 0.069% to 0.13%.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11175142,11175141 and 11105106)the National Hi-Tech Project of China (Grant No. 2009AA050705)the State Key Laboratory of Multiphase Flow (Xi’an Jiaotong University)
文摘An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 were obtained on this device, which enable it to be used for neutron detection in multi-radiation field. Moreover, the neutron sensitivity of this detector was characterized theoretically and experimentally. And for fast and ultra-fast neutron, the detection sensitivity is in the magnitude of 10^-17 to 10^-16 C cm^2/n with good stability and negligible pump effect. All these results indicate that the as-prepared sensor to be ideal for fast and ultra-fast neutron monitoring, and it may pave the way to build neutron detector with low cost and large sensitive area with diamond.
