A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two exam...A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two examples of real radiation system optimization processes for China-made medical electron linac are provided： 15 MV X- ray system of BJ-20 linac, and 12 MeV electron system of BJ-14. Results are verified by using the traditional method.展开更多
To evaluae small animal imaging with individual different high voltage, filter thickness and tube current, an animal X-ray micro-computed tomography （micro-CT） system based on panel detector is developed and a rat i...To evaluae small animal imaging with individual different high voltage, filter thickness and tube current, an animal X-ray micro-computed tomography （micro-CT） system based on panel detector is developed and a rat is scanned by using the system with individual high voltage, tube current, filter thickness, and exposure time. A model is presented based on the Monte Carlo code PENELOPE for generating the X-ray spectra of X-ray tube used in the micro-CT system. A platform developed based on Matlab allows for calculating beam quality parameters, including the average energy of X-ray beam, the change of transmition rate and the input X-ray fluence. The factors affecting the signal difference to noise ratio （SDNR） of micro-CT are investigated and the relationship between SDNR and scan combinations is analyzed. A series of tools and methods are developed for small animal imaging and imaging performance evaluation in the field of small animal imaging.展开更多
文章分析了全球首个全面系统地评价开放政府数据的项目Open Data Barometer,对该项目使用的评价指标和评价方法进行了全面深入的剖析。基于本文的分析,比较了在开放政府数据中得分最高排在首位的英国以及排位靠后的中国的各项指标的得...文章分析了全球首个全面系统地评价开放政府数据的项目Open Data Barometer,对该项目使用的评价指标和评价方法进行了全面深入的剖析。基于本文的分析,比较了在开放政府数据中得分最高排在首位的英国以及排位靠后的中国的各项指标的得分情况,看到了中国与英国之间的开放鸿沟(Open Divide)主要体现在:(1)中国在国家层面没有明确的开放政府数据计划;(2)关键数据集的开放程度很低;(3)关于开放政府数据的影响,有力的证据几乎没有。通过比较这些详细指标的得分情况,能让我们更加清楚地认识到中国开放政府数据在哪些方面存在不足。展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.10527003,60672104the National Basic Research Program of China under Grant No.2006CB705705+2 种基金the Joint Research Subject of Beijing Education Committee of China under Grant No.JD100010607the Beijing Municipal Natural Science Foundation of China under Grant No.3073019the Upgrading Subject of Instrument in Science and Technological Ministry of China under Grant No.2006JG1000~~
基金Supported by the National Natural Science Foundation of China (60672104,10675013)the Na-tional Basic Research Program of China ("973"Program)(2006CB705705)+1 种基金the 10th Five-Year Plan of the Ministry of Science and Technology of China(2001BA706B-05)the Joint Research Foundation of Beijing Municipal Commissionof Education~~
文摘A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two examples of real radiation system optimization processes for China-made medical electron linac are provided： 15 MV X- ray system of BJ-20 linac, and 12 MeV electron system of BJ-14. Results are verified by using the traditional method.
基金Supported by the National Natural Science Foundation of China (60672104,10527003)the Nation-al Basic Research Program of China ("973"Program)(2006CB705705)the Joint Research Foundation of Beijing Mu-nicipal Commission of Education (JD100010607)~~
文摘To evaluae small animal imaging with individual different high voltage, filter thickness and tube current, an animal X-ray micro-computed tomography （micro-CT） system based on panel detector is developed and a rat is scanned by using the system with individual high voltage, tube current, filter thickness, and exposure time. A model is presented based on the Monte Carlo code PENELOPE for generating the X-ray spectra of X-ray tube used in the micro-CT system. A platform developed based on Matlab allows for calculating beam quality parameters, including the average energy of X-ray beam, the change of transmition rate and the input X-ray fluence. The factors affecting the signal difference to noise ratio （SDNR） of micro-CT are investigated and the relationship between SDNR and scan combinations is analyzed. A series of tools and methods are developed for small animal imaging and imaging performance evaluation in the field of small animal imaging.
文摘文章分析了全球首个全面系统地评价开放政府数据的项目Open Data Barometer,对该项目使用的评价指标和评价方法进行了全面深入的剖析。基于本文的分析,比较了在开放政府数据中得分最高排在首位的英国以及排位靠后的中国的各项指标的得分情况,看到了中国与英国之间的开放鸿沟(Open Divide)主要体现在:(1)中国在国家层面没有明确的开放政府数据计划;(2)关键数据集的开放程度很低;(3)关于开放政府数据的影响,有力的证据几乎没有。通过比较这些详细指标的得分情况,能让我们更加清楚地认识到中国开放政府数据在哪些方面存在不足。
