Results 81 to 90 of about 595 (150)
Dianci bileiqi, 2016 由雷电引起的浪涌电压和电流是造成电子设备失效甚至损坏的主要因素。雷电辐射电磁场的水平电场分量在雷电瞬态过电压的研究计算中占据重要位置,然而目前针对雷电辐射水平电场的近似算法均是将地表假设成光滑地表,但现实中的地表常常存在高低起伏的特征。针对上述问题,基于Cooray-Rubinstein算法（简称C-R算法）提出了一种适用于二维分形粗糙地表的雷电水平场计算的新算法,并利用三维时域有限差分方法对其适用范围和精度进行了检验。结果表明:相比于光滑地表,粗糙地表对雷电水平电场的衰减不容忽视 ...
刘涛, 李东帅, 张其林
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Quantitative Computed Tomography Study of Bone Mineral Density for Adults Residents in Foshan [PDF]
Objective: To study the relation between adult vertebral bone mineral density (BMD) and gender and age in Foshan, to explore the average BMD of each age group and osteoporosis (OP) incidence distribution in the region.
Cuiling ZHU +4 more
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Zhongshan Daxue xuebao. Yixue kexue ban, 2011 【目的】 初步调查介入放射治疗的患者术中所受X射线辐射的剂量并探讨降低辐射的方法【方法】 采用DSA 机配置的穿透电离室型剂量监测系统(AEP),实时读取记录947名患者在1651例次介入放射操作中的透视时间摄影帧数面积-剂量乘积(DAP)和入射表面剂量(ESD),运用秩和检验关联性分析及线性回归分析等统计学方法分析以上数据,比较分析各种不同类型患者介入操作辐射数据的差异性及相互关系【结果】 患者的透视时间摄影帧数DAPESD的均值分别为(13.5 ± 12.1) min(230 ± 180)帧(194
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Dianci bileiqi, 2018 针对强风导致紧凑型输电线路各相导线间间隙距离减小而发生的闪络情况,分别采用了辐射交联聚烯烃材料的母排热缩管和优质硅橡胶材料的卡扣式绝缘护套管,提出了将其安装在输电线路上来进一步增大输电线路相间放电距离的方法。建立了模拟输电线路风偏放电试验的物理模型,在不同间距情况下,对裸电线和裸导线分别双根包覆绝缘护套进行导线间空气间隙工频击穿试验。试验结果表明:裸导线空气间隙工频击穿电压与间隙距离近似呈线性关系,这与棒-棒间隙相似。裸导线双根包覆不同绝缘护套后,击穿电压提升都很明显,但卡扣式硅橡胶管安装更为方便 ...
彭永晶 +5 more
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Evolving Characters of Fukushima-derived 134,137Cs in Marine Environment: Decadal Analysis of Most Polluted Port near FDNPP [PDF]
A large amount of artificial radionuclides have been released into the ocean, contributing to serious nuclear pollution in marine environment, and arising public concerns and worry around the world. The Fukushima-derived artificial radionuclides can also
LIN Wuhui1, , ZHANG Yibang2, 3, DU Jinqiu3, LUO Zhu4, CAO Shaofei5, TUO Fei6
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Dianci bileiqi, 2018 针对正负地闪准确区分识别技术手段较难的缺陷,对闪电电场的波形进行了分析,对地闪回击波形的参数特征进行了分析和统计,并研究闪电放电类型的自动识别。利用时间分辨率为50 ns的快天线电场变化和126 MHz甚高频（VHF）辐射资料,对雷暴过程中闪电的波形进行时域特征分析。通过对闪电电场波形数据的分析,给出了识别地闪回击的依据,设定回击的上升时间在120μs之间,下降时间在2.5500μs之间,编写程序实现回击的自动识别,并进行了实际测试。结果表明,自动识别程序对负地闪回击的识别效率可达95 ...
赵冲, 王宁, 张瑾
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Positioning technique of coded aperture radiation imaging [PDF]
With the widespread application of nuclear technology and radiation protection, the demand for radioactive sources imaging is increasing. As a high-precision imaging and positioning device for radioactive sources, the coded aperture imaging positioning ...
ANG Wensheng +4 more
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Dianci bileiqi, 2017 针对传输线耦合雷电电磁波形成过电压对电子设备造成干扰及损坏的问题,将雷电闪电通道等效为辐射线天线,建立雷电回击通道、传输线、大地一体化模型,利用传输线模型所得理论推导公式与试验相结合的方法,对传输线耦合自然界雷电与模拟雷电进行对比分析,并计算了传输线耦合雷电电磁波形成过电压波形的幅值及能量。得出:当雷电回击通道中雷电流在5 kA45 kA范围时,传输线耦合雷电电磁波形成的过电压幅值与雷电流大小呈较好的线性关系,耦合的能量与雷电流大小呈幂函数关系;雷电过电压在传输线传输过程中激励出高频分量电压 ...
兰海燕
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Crosstalk interference and correction methods for low background gas-flow proportional counter [PDF]
The crosstalk phenomenon and its influence in the determination of gross α and β radioactivity when using a low background gas-flow proportional counter as a measuring instrument was examined in this paper. The crosstalk ratio between α and β channel was
GUO Xiaomin +4 more
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