在建的上海硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)的加速器隧道内,采用束流刮束器刮掉束晕外围张角比较大的电子,刮束器的束流损失率为0.1‰。本文采用蒙特卡洛程序FLUKA,用SO...在建的上海硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)的加速器隧道内,采用束流刮束器刮掉束晕外围张角比较大的电子,刮束器的束流损失率为0.1‰。本文采用蒙特卡洛程序FLUKA,用SOURCE程序实现电子束在3σbeam外的高斯分布,以尽量真实模拟电子在束流刮束器处的丢失情况,解决了低功率刮束情况下蒙特卡洛模拟无统计性结果的难题。利用束流环形高斯模型对刮束器的活化进行了分析,结果表明环形高斯模型可以更真实地再现电子在束流刮束器的丢失情况;5年运行后距刮束器30 cm处的剩余剂量率达到了数百μSv/h至数mSv/h,和国外类似装置计算结果相当;通过对放射性核素的种类分析,结果证明刮束器(钨)的放射性废物处置难度不大。展开更多
For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial ...For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial temperature is near the melting point. The deviation fit is smaller than 8% when the time is below 2x104 s. Comparison between the predictions and the reported experimental data of thermal storage time at same conditions is investigated and good agreements have been got. Based on this method, the performance of the thermal storage unit and the role of natural convection are also investigated. Results show a linear relation between the maximum amount of stored heat and thermal storage time, and their ratio increases with the height of the thermal storage unit. As the thickness of the cavity increases, natural convection plays an increasingly important role in promoting the melting behavior of paraffin. When the thickness of the cavity is small, natural convection restrains the melting behavior of paraffin.展开更多
Path planning and formation structure forming are two of the most important problems for autonomous underwater vehicles(AUVs) to collaborate with each other.In this work,a dynamic formation model was proposed,in which...Path planning and formation structure forming are two of the most important problems for autonomous underwater vehicles(AUVs) to collaborate with each other.In this work,a dynamic formation model was proposed,in which several algorithms were developed for the complex underwater environment.Dimension changeable particle swarm algorithm was used to find an optimized path by dynamically adjusting the number and the distribution of the path nodes.Position relationship based obstacle avoidance algorithm was designed to detour along the edges of obstacles.Virtual potential point based formation-keeping algorithm was employed by incorporating dynamic strategies which were decided by the current states of the formation.The virtual potential point was used to keep the formation structure when the AUV or the formation was deviated.Simulation results show that an optimal path can be dynamically planned with fewer path nodes and smaller fitness,even with a concave obstacle.It has been also proven that different formation-keeping strategies can be adaptively selected and the formation can change its structure in a narrow area and restore back after passing the obstacle.展开更多
文摘在建的上海硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)的加速器隧道内,采用束流刮束器刮掉束晕外围张角比较大的电子,刮束器的束流损失率为0.1‰。本文采用蒙特卡洛程序FLUKA,用SOURCE程序实现电子束在3σbeam外的高斯分布,以尽量真实模拟电子在束流刮束器处的丢失情况,解决了低功率刮束情况下蒙特卡洛模拟无统计性结果的难题。利用束流环形高斯模型对刮束器的活化进行了分析,结果表明环形高斯模型可以更真实地再现电子在束流刮束器的丢失情况;5年运行后距刮束器30 cm处的剩余剂量率达到了数百μSv/h至数mSv/h,和国外类似装置计算结果相当;通过对放射性核素的种类分析,结果证明刮束器(钨)的放射性废物处置难度不大。
基金Projects(51666006,51406071,51174105,51366005)supported by the National Natural Science Foundation of ChinaProject(2014CB460605)supported by the National Basic Research Program of China
文摘For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial temperature is near the melting point. The deviation fit is smaller than 8% when the time is below 2x104 s. Comparison between the predictions and the reported experimental data of thermal storage time at same conditions is investigated and good agreements have been got. Based on this method, the performance of the thermal storage unit and the role of natural convection are also investigated. Results show a linear relation between the maximum amount of stored heat and thermal storage time, and their ratio increases with the height of the thermal storage unit. As the thickness of the cavity increases, natural convection plays an increasingly important role in promoting the melting behavior of paraffin. When the thickness of the cavity is small, natural convection restrains the melting behavior of paraffin.
基金Project(NS2013091)supported by the Basis Research Fund of Nanjing University of Aeronautics and Astronautics,China
文摘Path planning and formation structure forming are two of the most important problems for autonomous underwater vehicles(AUVs) to collaborate with each other.In this work,a dynamic formation model was proposed,in which several algorithms were developed for the complex underwater environment.Dimension changeable particle swarm algorithm was used to find an optimized path by dynamically adjusting the number and the distribution of the path nodes.Position relationship based obstacle avoidance algorithm was designed to detour along the edges of obstacles.Virtual potential point based formation-keeping algorithm was employed by incorporating dynamic strategies which were decided by the current states of the formation.The virtual potential point was used to keep the formation structure when the AUV or the formation was deviated.Simulation results show that an optimal path can be dynamically planned with fewer path nodes and smaller fitness,even with a concave obstacle.It has been also proven that different formation-keeping strategies can be adaptively selected and the formation can change its structure in a narrow area and restore back after passing the obstacle.
