Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate...Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate multi-arrival traveltime. This migration method takes into account both imaging accuracy and computational efficiency. Kirchhoff beam migration employs coarse grid techniques in several key steps such as traveltime calculation, weight function calculation, and imaging calculation. The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging method. This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets.展开更多
Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheatin...Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.展开更多
In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of...In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of 4.86 GHz. This frequency band has been reported for the breast cancer hyperthermia therapy. The grid long and short sides are responsible for the undesired cross-polarized radiation and desired copolarized radiation, respectively. The unsuitability of the conventional grid antenna array is ensured by investigating its radiation properties. The proposed grid antenna array short side width is varied and its long side width is kept wide as possible to enhance the radiation properties and to reduce the losses. Also, a reflector has been used for gain enhancement purpose. The proposed grid antenna array achieves side lobe level and 3 dB beam width of —27.9 dB and 25.9° for the E-plane and —27.9 dB and 26.3° for the H-plane, respectively. The breast phantom is irradiated by both proposed and conventional grid antenna arrays for 10 minutes. The proposed grid antenna array achieves 8°C temperature increase within the breast phantom area compared to 2°C temperature increase for conventional one. The proposed grid antenna array is highly efficient, high gain and light weight, and it has a very suitable radiation property for hyperthermia breast cancer therapy.展开更多
A 2D hybrid-PIC simulation model is proposed to investigate the beam extraction phenomena of the ion thruster. In which the electrons of the plasma sheath upstream the accelerator grid are assumed as particles while t...A 2D hybrid-PIC simulation model is proposed to investigate the beam extraction phenomena of the ion thruster. In which the electrons of the plasma sheath upstream the accelerator grid are assumed as particles while the downstream are fluid for improving the calculation efficiency. The ion transparency, plasma sheath formation, ion beam extraction characteristic of a two- and three-grid system have been compared in detail in this paper. From the comparison of the appearing time of the under-perveance phenomena in the two- and three-grid system, it illustrated that the two grid system has the wider operation range of the plasma densities than the three-grid one.展开更多
In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions ...In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions for probe measurement, avoids the differential operation on the I-V characteristics of multi-grid probe measurement; and by this method, the ion average velocity can be figured out directly by the I-V characteristics of multi-grid probe measurement.展开更多
基金Supported by projects of the Natural Science Foundation of China(No.41804100)the China Postdoctoral Science Foundation(No.2018M640910)the Fundamental Research Funds for the Central Universities(No.2682018CX36)
文摘Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate multi-arrival traveltime. This migration method takes into account both imaging accuracy and computational efficiency. Kirchhoff beam migration employs coarse grid techniques in several key steps such as traveltime calculation, weight function calculation, and imaging calculation. The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging method. This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets.
基金supported by National Natural Science Foundation of China(No.11575240)Key Program of Research and Development of Hefei Science Center,CAS(grant 2016HSC-KPRD002)
文摘Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.
文摘In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of 4.86 GHz. This frequency band has been reported for the breast cancer hyperthermia therapy. The grid long and short sides are responsible for the undesired cross-polarized radiation and desired copolarized radiation, respectively. The unsuitability of the conventional grid antenna array is ensured by investigating its radiation properties. The proposed grid antenna array short side width is varied and its long side width is kept wide as possible to enhance the radiation properties and to reduce the losses. Also, a reflector has been used for gain enhancement purpose. The proposed grid antenna array achieves side lobe level and 3 dB beam width of —27.9 dB and 25.9° for the E-plane and —27.9 dB and 26.3° for the H-plane, respectively. The breast phantom is irradiated by both proposed and conventional grid antenna arrays for 10 minutes. The proposed grid antenna array achieves 8°C temperature increase within the breast phantom area compared to 2°C temperature increase for conventional one. The proposed grid antenna array is highly efficient, high gain and light weight, and it has a very suitable radiation property for hyperthermia breast cancer therapy.
基金supported by National Natural Science Foundation of China (No. 11702123)Technology Based Research Projects of SASTIND (No. JSZL2017203B008)Fund for Distinguished Young Talents of CAST (No. 9140C550206130C55003)
文摘A 2D hybrid-PIC simulation model is proposed to investigate the beam extraction phenomena of the ion thruster. In which the electrons of the plasma sheath upstream the accelerator grid are assumed as particles while the downstream are fluid for improving the calculation efficiency. The ion transparency, plasma sheath formation, ion beam extraction characteristic of a two- and three-grid system have been compared in detail in this paper. From the comparison of the appearing time of the under-perveance phenomena in the two- and three-grid system, it illustrated that the two grid system has the wider operation range of the plasma densities than the three-grid one.
基金National Natural Science Foundation of China(No.50676026)
文摘In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions for probe measurement, avoids the differential operation on the I-V characteristics of multi-grid probe measurement; and by this method, the ion average velocity can be figured out directly by the I-V characteristics of multi-grid probe measurement.
