作者机构:
南华大学核科学与技术学院 衡阳 421001;核能与核技术工程虚拟仿真实验教学中心 衡阳 421001;[刘佩琪; 于涛; Zeng W.; 谢超; 赵鹏程; 谢金森; 陈珍平; 刘紫静] School of Nuclear Science and Technology, University of South China, Hengyang, 421001, China, Nuclear Power and Technology Engineering Virtual Simulation Experiment and Teaching Center, Hengyang, 421001, China
通讯机构:
[Yu, T.] S;School of Nuclear Science and Technology, University of South China, Hengyang, China
摘要:
To understand the physical and chemical characteristics, particle size distribution and sources of size-separated aerosols in Lhasa, which is located on the Tibetan Plateau (TP), six sizes of aerosol samples were collected in Lhasa in 2014. Ca(2+), NH4(+), NO3(-), SO4(2-) and Cl(-) were the dominant ions. The ratio of cation equivalents (CE) to anion equivalents (AE) for each particle size segment indicated that the atmospheric aerosols in Lhasa were alkaline. SO4(2-) and NO3(-) could be neutralized by Ca(2+), but could not be neutralized by NH4(+), according to the [NH4(+)]/[NO3(-)+SO4(2-)] and [Ca(2+)]/[NO3(-)+SO4(2-)] ratios. Mobile sources were dominant in PM0.95-1.5, PM1.5-3 and PM3-7.2, while stationary sources were dominant in the other three size fractions according to the [NO3(-)]/[SO4(2-)] ratios. The particle size distribution of all water-soluble ions during monsoon and non-monsoon periods was characterized by a bimodal distribution due to the different sources and formation mechanisms, and it was revealed that different ions had different sources in different seasons and different particle size segments by combining particle size distribution with correlation analysis. Source analysis of aerosols in Lhasa was performed using the Principal component analysis (PCA) for the first time, which revealed that combustion sources, motor vehicle exhaust, photochemical reaction sources and various types of dust were the main sources of Lhasa aerosols. Furthermore, Lhasa's air quality was also affected by long-distance transmission, expressed as pollutants from South Asia and West Asia, which were transmitted to Lhasa according to backward trajectory analysis.
摘要:
目的通过形变配准及刚性配准进行左侧乳腺癌放疗中靶区及危及器官剂量累加的研究,探讨二者受量的变化规律。方法回顾分析16例女性左侧乳腺癌根治术后患者,靶区包括锁上淋巴结引流区加胸壁,均采用6 MV X射线调强放疗(IMRT)。所有患者均接受定位、二程CT扫描,在定位图像(CT1)上制定放疗计划为Planl,在二程定位图像(CT2)上制定放疗计划为Plan2。利用Velocity软件将Plan2的剂量进行刚性、形变配准到CT1剂量累加后获得Planrigid、Plan-deform。比较4个计划中靶区及危及器官的剂量学差异。结果CT2比CT1的CTV体积平均缩小6.64%;形变后靶区剂量均匀性指数(HI)提高23.05%,而形变后心脏、左、右肺戴斯相似系数(DSC)均低于形变前(0.94±0.01 vs. 0.89±0.05、0.96 ±0.01 vs. 0.91±0.03、0.96±0.01 vs. 0.92±0.03),且差异均有统计学意义(Z = -3.208、-3.533、-3.535,P<0.05);心脏及左肺各剂量-体积指标在Plan2、Plan-rigid 、 Plan-deform与Plan1的组间差异均无统计学意义(P>0.05);在Plan-rigid组各剂量-体积指标均高于Plan-deform组。结论靶区及危及器官体积、剂量-体积指标变化较小的左乳癌根治术后患者在进行放疗剂量累加时,推荐使用刚性配准,且初次调强计划的剂量-体积指标可基本反映双肺及心脏的受量情况。
通讯机构:
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, Hunan Province Key Laboratory of Green Development Technology for Extremely Low Grade Uranium Resources, University of South China, Hengyang, China
作者机构:
[杜尚勉; Zeng, Wenjie; 于涛; 陈乐至; 谢金森] School of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;[杜尚勉; Zeng, Wenjie; 于涛; 陈乐至; 谢金森] Hunan;[杜尚勉; Zeng, Wenjie; 于涛; 陈乐至; 谢金森] 421001, China
摘要:
本文阐述了单球中子谱仪的原理,介绍了基于单慢化球和19对6Li-7Li闪烁体探测器构成的单球中子谱仪的结构及解谱方法,使用蒙特卡罗中子榆运程序模拟了单球中子谱仪的中子响应函数.计算结果表明,该谱仪具有较好的空间对称性,能根据谱仪中各探测器的计数对源的大致方位进行判断;模拟了单球谱仪在241 Am-Be源照射下各探测器的计数,使用Unfolding with Maxed and Gravel (UMG)解谱程序在不同解谱算法以及初始谱的情况下对模拟数据进行解谱计算,在使用最大熵散发以及与源项相同的预置谱的情况下,解谱结果最为准确,验证了响应函数的准确性.
摘要:
新型多层厚型气体电子倍增器(Multi-layers THick Gas Electron Multiplier,M-THGEM)和传统THGEM(厚型气体电子倍增器)相比,具有连续的雪崩区,能够在低气压和低电压下都有较高增益,结构更紧凑,易于大面积制作等优势。对M-THGEM探测器的工作原理及性能进行了模拟研究,首先通过有限元(ANSYS)软件对二层与三层结构的M-THGEM进行了建模,对电场和电势分布分别进行了模拟计算;再利用Garfield++程序包对M-THGEM探测器在不同低气压和不同工作电压下的增益、感生信号、正离子反馈率等性能进行了研究。模拟结果表明,三层结构M-THGEM在低气压(200 Torr)、纯He气体条件下,能够获得较稳定的增益(10~5),输出信号的宽度在12 ns左右;同时,为降低正离子反馈率,本工作提出并研究了一种非对称的电压施加方式,结果表明,这种施加方式能有效降低正离子的反馈率。
作者机构:
[刘红娟; 吴仁杰] Institute of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;[谢水波] Key Discipline Laboratory for National Defence for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang;[刘迎九] Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, University of South China, Hengyang
通讯机构:
[Xie, S.-B.] K;Key Discipline Laboratory for National Defence for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, Hunan, China