Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal...Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal surface coat and the size of active area of the source have considerable influence on the alpha energy spectrum of the source.展开更多
The Qianguo Ms5. 8 earthquake swarm of 2013 occurred in Qianguo, Jilin Province, China. There are five earthquakes with Ms ≥5. 0 in the Qianguo earthquake swarm, with magnitudes of Ms 5. 5, Ms 5. 0, Ms 5. 3, Ms 5. 8 ...The Qianguo Ms5. 8 earthquake swarm of 2013 occurred in Qianguo, Jilin Province, China. There are five earthquakes with Ms ≥5. 0 in the Qianguo earthquake swarm, with magnitudes of Ms 5. 5, Ms 5. 0, Ms 5. 3, Ms 5. 8 and Ms 5. 0. In this study, the far-field seismic radiated energy characteristics of the earthquakes are compared based on the source spectrum and the ground motion spectrum of the earthquake swarm. The ground motion spectrum of the five earthquakes at Changchun seismic station （CN2）, which is the national standard station, is first investigated with the recorded ground motions, and then the far-field seismic radiated energy is calculated and combined with the relationships of the source spectrum to describe the variable characteristics of the Qianguo earthquake swarm. Research results indicate that the second earthquake （No. 2） with Ms5. 0 is the key event of the earthquake swarm, which occurred on October 31, the same day following the first Ms5. 5 earthquake （No.l）. In fact, the magnitude of event No. 2 decreased compared to event No.l, which did not agree with its large far-field seismic radiated energy. It needs to be pointed out that event No. 2 was the turning point event of the Qianguo earthquake swarm, as being a significant transition before the largest Ms5. 8 earthquake.展开更多
A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and a Si（Au）surface barrier detector is presented. An iteration algorithm for unfolding the recoil proton energy spectrum to th...A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and a Si（Au）surface barrier detector is presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the neutron energy spectrum is investigated. The response matrices R of the polyethylene film at angles of 0o and45o were obtained by simulating the recoil proton energy spectra from mono-energetic neutrons using the MCNPX code. With an assumed D-T neutron spectrum, the recoil proton spectra from the polyethylene film at angles of 0oand 45owere also simulated using the MCNPX code. Based on the response matrices R and the simulated recoil proton spectra at 0oand 45o, the respective unfolded neutron spectra were obtained using the iteration algorithm,and compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement using the recoil proton method.展开更多
<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in ene...<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.展开更多
The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoi...The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoing from this kind of sources in light of radiation safety and the present technology. The yielded results show that 241Am leak has not been found when the peak energy of the alpha energy spectrum of this kind of sources is less than 4.96 MeV.展开更多
目的探讨双源CT能谱曲线在食管癌诊断及其病理分级中的应用价值。方法 60例经内镜或病理证实的食管癌患者行双源双能量模式扫描,两个球管管电压分别为:A球管100 k V,B球管140 k V,双能量扫描时两组球管同时工作。将扫描获得的两组数据...目的探讨双源CT能谱曲线在食管癌诊断及其病理分级中的应用价值。方法 60例经内镜或病理证实的食管癌患者行双源双能量模式扫描,两个球管管电压分别为:A球管100 k V,B球管140 k V,双能量扫描时两组球管同时工作。将扫描获得的两组数据上传至工作站进行相关后处理及分析:绘制食管癌病灶及正常食管管壁能谱曲线,比较食管癌病灶与正常食管壁、不同分化程度食管癌的能谱曲线特征及其斜率之间的差异与联系。食管癌病理分级依据病理结果。结果 1食管癌病灶能谱曲线走行位于正常食管管壁上方,并且斜率高于正常食管壁;2不同分化程度食管癌能谱曲线走行及趋势不同,分化程度越差,曲线走行越靠上,对各组能谱曲线斜率比较可得分化程度越差,能谱曲线斜率越大。结论双源双能量CT能谱曲线在食管癌诊断及病理分级中有着一定的临床应用价值。展开更多
文摘Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal surface coat and the size of active area of the source have considerable influence on the alpha energy spectrum of the source.
基金funded by the National Natural Science Foundation,China(Grant No.41404045,No.41504047)
文摘The Qianguo Ms5. 8 earthquake swarm of 2013 occurred in Qianguo, Jilin Province, China. There are five earthquakes with Ms ≥5. 0 in the Qianguo earthquake swarm, with magnitudes of Ms 5. 5, Ms 5. 0, Ms 5. 3, Ms 5. 8 and Ms 5. 0. In this study, the far-field seismic radiated energy characteristics of the earthquakes are compared based on the source spectrum and the ground motion spectrum of the earthquake swarm. The ground motion spectrum of the five earthquakes at Changchun seismic station （CN2）, which is the national standard station, is first investigated with the recorded ground motions, and then the far-field seismic radiated energy is calculated and combined with the relationships of the source spectrum to describe the variable characteristics of the Qianguo earthquake swarm. Research results indicate that the second earthquake （No. 2） with Ms5. 0 is the key event of the earthquake swarm, which occurred on October 31, the same day following the first Ms5. 5 earthquake （No.l）. In fact, the magnitude of event No. 2 decreased compared to event No.l, which did not agree with its large far-field seismic radiated energy. It needs to be pointed out that event No. 2 was the turning point event of the Qianguo earthquake swarm, as being a significant transition before the largest Ms5. 8 earthquake.
基金Supported by National Natural Science Foundations of China(11375077,21327801)National Key Scientific Instrument And Equipment Development Project(2013YQ40861)
文摘A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and a Si（Au）surface barrier detector is presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the neutron energy spectrum is investigated. The response matrices R of the polyethylene film at angles of 0o and45o were obtained by simulating the recoil proton energy spectra from mono-energetic neutrons using the MCNPX code. With an assumed D-T neutron spectrum, the recoil proton spectra from the polyethylene film at angles of 0oand 45owere also simulated using the MCNPX code. Based on the response matrices R and the simulated recoil proton spectra at 0oand 45o, the respective unfolded neutron spectra were obtained using the iteration algorithm,and compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement using the recoil proton method.
文摘<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.
文摘The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoing from this kind of sources in light of radiation safety and the present technology. The yielded results show that 241Am leak has not been found when the peak energy of the alpha energy spectrum of this kind of sources is less than 4.96 MeV.
文摘快速、准确定位振荡源是抑制电力系统强迫功率振荡的关键。为提高电力系统强迫振荡源定位精度和效率,该文提出一种基于耗散能量谱的电力系统强迫振荡源频域定位方法。该方法首先将电力系统广域测量信息进行短时傅里叶变换(short-time Fourier transform,STFT);然后,根据信号的时—频域特性,推导出时域耗散能量与时频域耗散能量间的关系,在此基础上,构建出频域耗散能量谱,论证了时域耗散能量与频域耗散能量谱的等价性;进而根据频域耗散能量谱辨识系统强迫振荡频率、定位强迫振荡源;最后,将所提方法应用到WECC179节点测试系统和ISO New England中进行仿真、验证,结果验证了所提方法的准确性和有效性。
文摘目的探讨双源CT能谱曲线在食管癌诊断及其病理分级中的应用价值。方法 60例经内镜或病理证实的食管癌患者行双源双能量模式扫描,两个球管管电压分别为:A球管100 k V,B球管140 k V,双能量扫描时两组球管同时工作。将扫描获得的两组数据上传至工作站进行相关后处理及分析:绘制食管癌病灶及正常食管管壁能谱曲线,比较食管癌病灶与正常食管壁、不同分化程度食管癌的能谱曲线特征及其斜率之间的差异与联系。食管癌病理分级依据病理结果。结果 1食管癌病灶能谱曲线走行位于正常食管管壁上方,并且斜率高于正常食管壁;2不同分化程度食管癌能谱曲线走行及趋势不同,分化程度越差,曲线走行越靠上,对各组能谱曲线斜率比较可得分化程度越差,能谱曲线斜率越大。结论双源双能量CT能谱曲线在食管癌诊断及病理分级中有着一定的临床应用价值。
