In this paper, we combine the method of constructing the compensating function introduced by Kawashima and the standard energy method for the study on the Landau equation with external forcing. Both the global existen...In this paper, we combine the method of constructing the compensating function introduced by Kawashima and the standard energy method for the study on the Landau equation with external forcing. Both the global existence of solutions near the time asymptotic states which are local Maxwellians and the optimal convergence rates are obtained. The method used here has its own advantage for this kind of studies because it does not involve the spectrum analysis of the corresponding linearized operator.展开更多
During the last few years,active personal dosimeters have been developed and have replaced passive personal dosimeters in some external monitoring systems,frequently using silicon diode detectors.Incident photons inte...During the last few years,active personal dosimeters have been developed and have replaced passive personal dosimeters in some external monitoring systems,frequently using silicon diode detectors.Incident photons interact with the constituents of the diode detector and produce electrons.These photon-induced electrons deposit energy in the detector＇s sensitive region and contribute to the response of diode detectors.To achieve an appropriate photon dosimetry response,the detectors are usually covered by a metallic layer with an optimum thickness.The metallic cover acts as an energy compensating shield.In this paper,a software process is performed for energy compensation.Selective data sampling based on pulse height is used to determine the photon dose equivalent.This method is applied to improve the energy response in photon dosimetry.The detector design is optimized for the response function and determination of the photon dose equivalent.Photon personal dose equivalent is determined in the energy range of 0.3-6 MeV.The error values of the calculated data for this wide energy range and measured data for ^133Ba,^137Cs,^60Co and ^241Am-Be sources respectively are up to 20%and 15%.Fairly good agreement is seen between simulation and dose values obtained from our process and specifications from several photon sources.展开更多
The resistivities of vanadium-doped semi-insulating 4H-SiC wafers were measured by a contactless resistivity measurement system. Anomalous resistivity was found in semi-insulating 4H-SiC wafer. Raman spectra of semi-i...The resistivities of vanadium-doped semi-insulating 4H-SiC wafers were measured by a contactless resistivity measurement system. Anomalous resistivity was found in semi-insulating 4H-SiC wafer. Raman spectra of semi-insulating4H-SiC wafer indicated that the anomalous resistivity was caused by polytype inclusion. Based on the activation energies of different SiC polytypes calculated from resistivity versus temperature data measured by COREMA-VT, the resistivities in the vanadium-doped semi-insulating 4H-SiC wafer with 6H polytype inclusion were calculated. The calculated resistivities are quite consistent with the measured resistivities. Furthermore, the compensation mechanism for the formation of anomalous resistivity was proposed.展开更多
基金supported by Strategic Research Grant of City University of Hong Kong, 7002129the Changjiang Scholar Program of Chinese Educational Ministry in Shanghai Jiao Tong University+1 种基金The research of the second author was supported partially by NSFC (10601018)partially by FANEDD
文摘In this paper, we combine the method of constructing the compensating function introduced by Kawashima and the standard energy method for the study on the Landau equation with external forcing. Both the global existence of solutions near the time asymptotic states which are local Maxwellians and the optimal convergence rates are obtained. The method used here has its own advantage for this kind of studies because it does not involve the spectrum analysis of the corresponding linearized operator.
文摘During the last few years,active personal dosimeters have been developed and have replaced passive personal dosimeters in some external monitoring systems,frequently using silicon diode detectors.Incident photons interact with the constituents of the diode detector and produce electrons.These photon-induced electrons deposit energy in the detector＇s sensitive region and contribute to the response of diode detectors.To achieve an appropriate photon dosimetry response,the detectors are usually covered by a metallic layer with an optimum thickness.The metallic cover acts as an energy compensating shield.In this paper,a software process is performed for energy compensation.Selective data sampling based on pulse height is used to determine the photon dose equivalent.This method is applied to improve the energy response in photon dosimetry.The detector design is optimized for the response function and determination of the photon dose equivalent.Photon personal dose equivalent is determined in the energy range of 0.3-6 MeV.The error values of the calculated data for this wide energy range and measured data for ^133Ba,^137Cs,^60Co and ^241Am-Be sources respectively are up to 20%and 15%.Fairly good agreement is seen between simulation and dose values obtained from our process and specifications from several photon sources.
基金financially supported by National Basic Research Program of China (No. 2011CB301904)the Natural Science Foundation of China (Nos. 11134006 and 61327808)
文摘The resistivities of vanadium-doped semi-insulating 4H-SiC wafers were measured by a contactless resistivity measurement system. Anomalous resistivity was found in semi-insulating 4H-SiC wafer. Raman spectra of semi-insulating4H-SiC wafer indicated that the anomalous resistivity was caused by polytype inclusion. Based on the activation energies of different SiC polytypes calculated from resistivity versus temperature data measured by COREMA-VT, the resistivities in the vanadium-doped semi-insulating 4H-SiC wafer with 6H polytype inclusion were calculated. The calculated resistivities are quite consistent with the measured resistivities. Furthermore, the compensation mechanism for the formation of anomalous resistivity was proposed.
