In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiat...In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.展开更多
图神经网络在基于知识图嵌入的推荐算法中面临数据稀疏和模型过平滑问题,而导致推荐系统难以捕捉用户潜在的长期偏好。针对该问题,提出了一种基于深度知识图卷积网络的推荐算法。首先,在利用历史交互数据构建知识图谱的基础上,通过随机...图神经网络在基于知识图嵌入的推荐算法中面临数据稀疏和模型过平滑问题,而导致推荐系统难以捕捉用户潜在的长期偏好。针对该问题,提出了一种基于深度知识图卷积网络的推荐算法。首先,在利用历史交互数据构建知识图谱的基础上,通过随机采样过程来获得知识图谱的多个视图以缓解交互数据稀疏的问题。其次,在知识图卷积操作过程中引入残差连接以缓解过平滑问题,从而构建一种深度知识图卷积网络以捕获高阶邻居信息并获得用户潜在的远程兴趣。同时,为了避免深层图卷积网络带来噪声输入问题,利用图自注意力机制对深层特征表示进行提纯。为验证模型的可行性和有效性,在3个真实数据集上进行了大量实验。实验结果表明,所提出的模型能够有效缓解过度平滑问题。在这3个数据集中,模型的ROC曲线下的面积(Area Under Curve,AUC,记为AUC)分别达到了0.974、0.812和0.732,相较于现有方法,模型的推荐准确度明显提升。展开更多
轻子散射实验是探索核子与原子核结构的理想工具。中国电子离子对撞机(Electron Ion Collider in China,EicC)建议书设想在已开建的强流重离子加速器装置(High Intensity heavy ion Accelerator Facility,HIAF)的基础上,升级质子束流为2...轻子散射实验是探索核子与原子核结构的理想工具。中国电子离子对撞机(Electron Ion Collider in China,EicC)建议书设想在已开建的强流重离子加速器装置(High Intensity heavy ion Accelerator Facility,HIAF)的基础上,升级质子束流为20 GeV的极化束流,并建造2.8~5 GeV极化电子束流,从而实现质心系能量为15~20 GeV的双极化电子-离子对撞。EicC设计的亮度为(2~4)×10^33cm^-2·s^-1,质子束流极化率达到70%,电子束流极化率达到80%。该装置除了能提供极化轻离子束流(例如:氦-3)外,也可产生非极化重离子束流(碳-12~铀-238)。EicC将聚焦核子海夸克部分子结构、原子核物质结构与性质、奇特强子态三个方面的物理研究。高亮度、高精度的对撞机有助于精确地测量核子结构函数并对核子进行三维成像,揭示强相互作用的动力学规律;原子核部分子分布包括核子短程关联以及原子核介质效应同样是该提案的重要科学目标;EicC能区接近重味夸克产生阈值,在研究重味强子谱方面拥有低背景的独特优势,有助于发现研究新的奇特强子态。质子质量起源问题也可以通过重味矢量介子的产生来研究。为了完成上述物理目标,我们将利用最先进的探测器技术建造接近全立体角覆盖的EicC对撞机谱仪。在准备EicC白皮书的过程中,我们得到世界各国专家的支持。EicC的物理与已有的实验和美国即将建设的EIC中的物理项目相互补充。EicC的建成及运行有望引领前沿的中高能核物理研究,使我国在加速器和探测器先进技术等领域实现跨越式发展,为我国核物理与强子物理以及相关科学领域提供大型综合实验平台与人才培养基地。展开更多
基金Supported by National Key R&D Program of China(2019YFA0405400)。
文摘In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.
文摘图神经网络在基于知识图嵌入的推荐算法中面临数据稀疏和模型过平滑问题,而导致推荐系统难以捕捉用户潜在的长期偏好。针对该问题,提出了一种基于深度知识图卷积网络的推荐算法。首先,在利用历史交互数据构建知识图谱的基础上,通过随机采样过程来获得知识图谱的多个视图以缓解交互数据稀疏的问题。其次,在知识图卷积操作过程中引入残差连接以缓解过平滑问题,从而构建一种深度知识图卷积网络以捕获高阶邻居信息并获得用户潜在的远程兴趣。同时,为了避免深层图卷积网络带来噪声输入问题,利用图自注意力机制对深层特征表示进行提纯。为验证模型的可行性和有效性,在3个真实数据集上进行了大量实验。实验结果表明,所提出的模型能够有效缓解过度平滑问题。在这3个数据集中,模型的ROC曲线下的面积(Area Under Curve,AUC,记为AUC)分别达到了0.974、0.812和0.732,相较于现有方法,模型的推荐准确度明显提升。
文摘轻子散射实验是探索核子与原子核结构的理想工具。中国电子离子对撞机(Electron Ion Collider in China,EicC)建议书设想在已开建的强流重离子加速器装置(High Intensity heavy ion Accelerator Facility,HIAF)的基础上,升级质子束流为20 GeV的极化束流,并建造2.8~5 GeV极化电子束流,从而实现质心系能量为15~20 GeV的双极化电子-离子对撞。EicC设计的亮度为(2~4)×10^33cm^-2·s^-1,质子束流极化率达到70%,电子束流极化率达到80%。该装置除了能提供极化轻离子束流(例如:氦-3)外,也可产生非极化重离子束流(碳-12~铀-238)。EicC将聚焦核子海夸克部分子结构、原子核物质结构与性质、奇特强子态三个方面的物理研究。高亮度、高精度的对撞机有助于精确地测量核子结构函数并对核子进行三维成像,揭示强相互作用的动力学规律;原子核部分子分布包括核子短程关联以及原子核介质效应同样是该提案的重要科学目标;EicC能区接近重味夸克产生阈值,在研究重味强子谱方面拥有低背景的独特优势,有助于发现研究新的奇特强子态。质子质量起源问题也可以通过重味矢量介子的产生来研究。为了完成上述物理目标,我们将利用最先进的探测器技术建造接近全立体角覆盖的EicC对撞机谱仪。在准备EicC白皮书的过程中,我们得到世界各国专家的支持。EicC的物理与已有的实验和美国即将建设的EIC中的物理项目相互补充。EicC的建成及运行有望引领前沿的中高能核物理研究,使我国在加速器和探测器先进技术等领域实现跨越式发展,为我国核物理与强子物理以及相关科学领域提供大型综合实验平台与人才培养基地。
