The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains t...The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions,that is,the same atomic population density and buffer gas pressure,which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations.Here,utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure,the height and full width at half maximum of electromagnetically induced transparency(EIT)signal,and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies(saturated laser power).It is identified that EIT signal height is proportional to the cell length,full width at half maximum and sensitivity grow with the increment of cell length to a certain extent.Employing the coherent integration signal theory and atomic linear expansion coefficient method,theoretical analysis of the EIT height and sensitivity are further investigated.The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement,communication,and imaging.展开更多
目的配准是术前影像引导的椎弓根螺钉内固定术中的重要环节。术前CT影像三维重建获得的点云和术中捕获的暴露部位点云重叠率低,易受噪声、遮挡等因素的干扰,使点云配准更具挑战性。本文采用局部特征和距离度量相结合的方式应对低重叠率...目的配准是术前影像引导的椎弓根螺钉内固定术中的重要环节。术前CT影像三维重建获得的点云和术中捕获的暴露部位点云重叠率低,易受噪声、遮挡等因素的干扰,使点云配准更具挑战性。本文采用局部特征和距离度量相结合的方式应对低重叠率配准问题。方法首先利用方向直方图描述子(signature of histograms of orientations,SHOT)和随机抽样一致算法(random sample consensus,RANSAC)提取并匹配几何特征相似的点,完成初始对齐。应用目标函数对称ICP,通过最小化对称化点到面目标函数得到最终变换矩阵。对来源于SpineWeb公开数据集的5组腰椎数据进行配准实验。结果术前术中点云配准实验中平均配准误差为0.128 mm,平均运行时间为5.750 s。结论实验结果验证了该算法在低重叠率术前术中点云配准中的有效性,使得外科医生能及时根据配准结果调整手术器械,从而提高椎弓根螺钉置入准确率。展开更多
为研究水下气泡运动与演化特性,对水中浮力作用下的单气泡及水平并列的两气泡上升过程分别进行数值模拟。采用VOF(volume of fluid)方法对气液两相的交界面进行追踪,考虑两相间的表面张力作用,计算不同时刻的气泡结构及其引起的两相流...为研究水下气泡运动与演化特性,对水中浮力作用下的单气泡及水平并列的两气泡上升过程分别进行数值模拟。采用VOF(volume of fluid)方法对气液两相的交界面进行追踪,考虑两相间的表面张力作用,计算不同时刻的气泡结构及其引起的两相流场。研究了气泡上升过程底部速度的变化规律,并分别与实验照片进行对比。结果表明,水下气泡上升过程底部持续向内凹陷,最后破裂为多个小气泡向水中扩散,并且尾流区出现明显的旋涡结构。模拟两气泡运动时发现气泡摇摆上升,最终未发生聚并。数值模拟结果与实验能很好吻合。该研究结果为水下气液两相流动的研究提供了一种可行的模拟方法。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61901495 and 12104509)
文摘The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions,that is,the same atomic population density and buffer gas pressure,which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations.Here,utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure,the height and full width at half maximum of electromagnetically induced transparency(EIT)signal,and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies(saturated laser power).It is identified that EIT signal height is proportional to the cell length,full width at half maximum and sensitivity grow with the increment of cell length to a certain extent.Employing the coherent integration signal theory and atomic linear expansion coefficient method,theoretical analysis of the EIT height and sensitivity are further investigated.The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement,communication,and imaging.
文摘目的配准是术前影像引导的椎弓根螺钉内固定术中的重要环节。术前CT影像三维重建获得的点云和术中捕获的暴露部位点云重叠率低,易受噪声、遮挡等因素的干扰,使点云配准更具挑战性。本文采用局部特征和距离度量相结合的方式应对低重叠率配准问题。方法首先利用方向直方图描述子(signature of histograms of orientations,SHOT)和随机抽样一致算法(random sample consensus,RANSAC)提取并匹配几何特征相似的点,完成初始对齐。应用目标函数对称ICP,通过最小化对称化点到面目标函数得到最终变换矩阵。对来源于SpineWeb公开数据集的5组腰椎数据进行配准实验。结果术前术中点云配准实验中平均配准误差为0.128 mm,平均运行时间为5.750 s。结论实验结果验证了该算法在低重叠率术前术中点云配准中的有效性,使得外科医生能及时根据配准结果调整手术器械,从而提高椎弓根螺钉置入准确率。
文摘为研究水下气泡运动与演化特性,对水中浮力作用下的单气泡及水平并列的两气泡上升过程分别进行数值模拟。采用VOF(volume of fluid)方法对气液两相的交界面进行追踪,考虑两相间的表面张力作用,计算不同时刻的气泡结构及其引起的两相流场。研究了气泡上升过程底部速度的变化规律,并分别与实验照片进行对比。结果表明,水下气泡上升过程底部持续向内凹陷,最后破裂为多个小气泡向水中扩散,并且尾流区出现明显的旋涡结构。模拟两气泡运动时发现气泡摇摆上升,最终未发生聚并。数值模拟结果与实验能很好吻合。该研究结果为水下气液两相流动的研究提供了一种可行的模拟方法。
