We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and...We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06±0.30 mas yr-1 in R.A. and -2.6±0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential.展开更多
The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were u...The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al.（2014）. This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.展开更多
The eigenvalues of a Ar<sub>3</sub> cluster subject to a Lennerd-Jones pairwise interaction arecalculated by using harmonic oscillator product states,The geometric structures and theinternal motion of a Ar...The eigenvalues of a Ar<sub>3</sub> cluster subject to a Lennerd-Jones pairwise interaction arecalculated by using harmonic oscillator product states,The geometric structures and theinternal motion of a Ar<sub>3</sub> cluster are investigated from an anaysis of the wavefunctions.Thisinvestigation reveals the general shape and motional features of a Ar<sub>3</sub> cluster.展开更多
Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swar...Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swarm motion.In the model,we added a polar alignment strength,along with Gaussian curvature,affecting particles swarm motion.We find that when the force exceeds a certain limit,the order parameter will decrease with the increase of the force.Combined with our definition of order parameter and observation of the model,the reason is that particles begin to move side by side under the influence of polar forces.In addition,the effects of velocity,rotational diffusion coefficient,and packing fraction on particle swarm motion are discussed.It is found that the rotational diffusion coefficient and the packing fraction have a great influence on the clustering motion of particles,while the velocity has little influence on the clustering motion of particles.展开更多
Using an appropriate approximation, we have formulated the interacting equation of multi-bubble motion for a system of a single bubble and a spherical bubble cluster. The behavior of the bubbles is observed in coupled...Using an appropriate approximation, we have formulated the interacting equation of multi-bubble motion for a system of a single bubble and a spherical bubble cluster. The behavior of the bubbles is observed in coupled and uncoupled states. The oscillation of bubbles inside the cluster is in a coupled state. The numerical simulation demonstrates that the secondary Bjerknes force can be influenced by the number density, initial radius, distance, driving frequency, and amplitude of ultrasound. However, if a bubble approaches a bubble cluster of the same initial radii, coupled oscillation would be induced and a repulsive force is evoked, which may be the reason why the bubble cluster can exist steadily. With the increment of the number density of the bubble cluster, a secondary Bjerknes force acting on the bubbles inside the cluster decreases due to the strong suppression of the coupled bubbles. It is shown that there may be an optimal number density for a bubble cluster which can generate an optimal cavitation effect in liquid for a stable driving ultrasound.展开更多
BACKGROUND： Multiple linear regression, general linear test and calculation of correlation values are commonly used in studies of brain function using functional magnetic resonance imaging （fMRI）. However, there ar...BACKGROUND： Multiple linear regression, general linear test and calculation of correlation values are commonly used in studies of brain function using functional magnetic resonance imaging （fMRI）. However, there are some limitations in their applications. In non-signal data statistics, cluster analysis functions as a very mature method, but it is not reliable in signal data statistics. OBJECTIVE： To investigate the spatial distribution of complex function in brain areas during motor tasks by cluster analysis, and to compare this with multiple linear regression. DESIGN, TIME AND SETTING： Block design, performed at the MR laboratory of Guangzhou University of Chinese Medicine. PARTICIPANTS： Fifteen right-handed, healthy university students （10 males and 5 females, aged 19-21 years）. METHODS： fMRI was performed while the subjects performed a finger movement task with the right hand. The screen showed a gray hand, with red spots presented in a random order on one of the index, middle, ring and little fingers. The subjects were required to remember the sequence of the red spots on the display. After a delay of 14 seconds, the subjects tapped their fingers according to the order of the red spots, as soon as the red spots turned green. After an interval of 14 seconds, another sequence appeared. Every sequence lasted for 28 seconds, including preparation and execution phases. A total of nine sequences per subject were performed. The data were analyzed using deconvolution and cluster methods, and program ＂cluster＂ was used to statistically analyze the coordinate positions of deconvolution and cluster data. MAIN OUTCOME MEASURES： Brain activation maps by deconvolution and brain function maps by clustering of the maximum peak values; blood oxygenation level dependent curves by deconvolution; coordinates of peak values and activation volumes by the two methods. RESULTS： The deconvolution method could not integrate the brain activation maps during different tasks into one activation picture, which made it difficult to identify exactly the spatial distribution of various activities in certain brain areas. Cluster analysis, using maximum peak values, clearly showed brain areas of monofunction and multifunction, even complex function, and presented a clear spatial distribution of multiple functional movements. Using the command ＂clust＂ with the same parameters, the volumes of main brain activation areas were consistent, indicating the maximum peak values are completely reliable in contrast to the deconvolution method. CONCLUSION： Cluster analysis is conducive to the analysis of multifunctional complex areas. Clustering using maximum peak values is a reliable method. Brain areas, such as primary motor cortex, supplementary motor area, and posterior parietal cortex, are not monofunctional areas, but multifunctional, complex ones. The activation maps derived by deconvolution statistics are distributed in many maps, which are not convenient to determine the functional distribution of complex brain areas.展开更多
On the reasonable hypothesis that the internal motions of member stars of a cluster are random and isotropic, a method which can be used to estimate the velocity distance of the cluster and its uncertainty is develope...On the reasonable hypothesis that the internal motions of member stars of a cluster are random and isotropic, a method which can be used to estimate the velocity distance of the cluster and its uncertainty is developed. The velocity distance so determined is an absolute distance estimate, and is completely independent of the （widely used） luminosity distance, which is a relative distance estimate. Using the published high-accuracy observational data of radial velocities and proper motions of the stars in the open cluster M11 region, we have determined the distance of M 11 to be 1.89 ± 0.52 kpc. This is in quite good agreement with the published luminosity distances of the cluster. We briefly discuss the problems concerned, including the sources of errors in the method and its applicable range.展开更多
The key pose frames of a human motion pose sequence,play an important role in the compression,retrieval and semantic analysis of continuous human motion.The current available clustering methods in literatures are diff...The key pose frames of a human motion pose sequence,play an important role in the compression,retrieval and semantic analysis of continuous human motion.The current available clustering methods in literatures are difficult to determine the number of key pose frames automatically,and may destroy the postures’ temporal relationships while extracting key frames.To deal with this problem,this paper proposes a new key pose frames extraction method on the basis of 3D space distances of joint points and the improved X-means clustering algorithm.According to the proposed extraction method,the final key pose frame sequence could be obtained by describing the posture of human body with space distance of particular joint points and then the time-constraint X-mean algorithm is applied to cluster and filtrate the posture sequence.The experimental results show that the proposed method can automatically determine the number of key frames and save the temporal characteristics of motion frames according to the motion pose sequence.展开更多
为防止船舶违规安装虚假船舶通信系统软件并用其模拟发送干扰船舶自动识别系统(automatic identification system,AIS)的信号,提出一种基于运动特征的双阶段虚假船舶通信系统检测算法(two-stage false ship communication system detect...为防止船舶违规安装虚假船舶通信系统软件并用其模拟发送干扰船舶自动识别系统(automatic identification system,AIS)的信号,提出一种基于运动特征的双阶段虚假船舶通信系统检测算法(two-stage false ship communication system detection algorithm based on motion features,FSMF)。FSMF算法分析虚假船舶通信系统与AIS同时开启和间隔开启两种干扰情况下的船舶运动轨迹特征,通过计算轨迹之间的时间重叠度将识别过程分为两个阶段。在第一阶段,将动态时间规整(dynamic time warping,DTW)方法应用于时间重叠度为0的轨迹,利用地理距离和动态距离判断轨迹相似性,识别出两者间隔开启时的异常船舶。在第二阶段,将聚类算法应用于时间重叠度大于0的轨迹,把聚成同一簇的轨迹识别为两者同时开启时的运动轨迹,进而识别出异常船舶。通过三种不同类型的数据集对FSMF算法进行性能验证。随机海域的AIS数据分析结果表明,该算法能够有效识别安装虚假船舶通信系统软件的异常船舶,提升船舶监控能力,降低潜在的安全风险。展开更多
基金NKBRSF19990754 and National Natural Sciences Foundation under grant 19833010．
文摘We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06±0.30 mas yr-1 in R.A. and -2.6±0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential.
基金supported by grant No.BG051 PO001-3.3.06-0057 of the European Social Fund
文摘The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al.（2014）. This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.
基金The project supported by the National Natural Science Foundation of ChinaGuangdong Provincial Natural Science Foundation of China
文摘The eigenvalues of a Ar<sub>3</sub> cluster subject to a Lennerd-Jones pairwise interaction arecalculated by using harmonic oscillator product states,The geometric structures and theinternal motion of a Ar<sub>3</sub> cluster are investigated from an anaysis of the wavefunctions.Thisinvestigation reveals the general shape and motional features of a Ar<sub>3</sub> cluster.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12075090 and 12005066)the Science and Technology Program of Guangzhou(Grant No.2019050001)+1 种基金the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030313029)the Major Basic Research Project of Guangdong Province,China(Grant No.2017KZDXM024)。
文摘Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swarm motion.In the model,we added a polar alignment strength,along with Gaussian curvature,affecting particles swarm motion.We find that when the force exceeds a certain limit,the order parameter will decrease with the increase of the force.Combined with our definition of order parameter and observation of the model,the reason is that particles begin to move side by side under the influence of polar forces.In addition,the effects of velocity,rotational diffusion coefficient,and packing fraction on particle swarm motion are discussed.It is found that the rotational diffusion coefficient and the packing fraction have a great influence on the clustering motion of particles,while the velocity has little influence on the clustering motion of particles.
基金Project supported by the National Basic Research Program of China (Grant Nos. 2010CB327803 and 2012CB921504)the National Natural Science Foundation of China (Grant Nos. 11174138, 81127901, 11174139, and 11204168)+1 种基金the Fundamental Research Funds for the Central Universities of China (Grant Nos. GK201002009 and GK201004003)the Natural Science Foundation of Shaanxi Province, China (Grant No. 2010JQ1006)
文摘Using an appropriate approximation, we have formulated the interacting equation of multi-bubble motion for a system of a single bubble and a spherical bubble cluster. The behavior of the bubbles is observed in coupled and uncoupled states. The oscillation of bubbles inside the cluster is in a coupled state. The numerical simulation demonstrates that the secondary Bjerknes force can be influenced by the number density, initial radius, distance, driving frequency, and amplitude of ultrasound. However, if a bubble approaches a bubble cluster of the same initial radii, coupled oscillation would be induced and a repulsive force is evoked, which may be the reason why the bubble cluster can exist steadily. With the increment of the number density of the bubble cluster, a secondary Bjerknes force acting on the bubbles inside the cluster decreases due to the strong suppression of the coupled bubbles. It is shown that there may be an optimal number density for a bubble cluster which can generate an optimal cavitation effect in liquid for a stable driving ultrasound.
基金the Key Program of Guangzhou Educational Bureau in the Eleventh Five-Year Plan, No. 06TJZ014
文摘BACKGROUND： Multiple linear regression, general linear test and calculation of correlation values are commonly used in studies of brain function using functional magnetic resonance imaging （fMRI）. However, there are some limitations in their applications. In non-signal data statistics, cluster analysis functions as a very mature method, but it is not reliable in signal data statistics. OBJECTIVE： To investigate the spatial distribution of complex function in brain areas during motor tasks by cluster analysis, and to compare this with multiple linear regression. DESIGN, TIME AND SETTING： Block design, performed at the MR laboratory of Guangzhou University of Chinese Medicine. PARTICIPANTS： Fifteen right-handed, healthy university students （10 males and 5 females, aged 19-21 years）. METHODS： fMRI was performed while the subjects performed a finger movement task with the right hand. The screen showed a gray hand, with red spots presented in a random order on one of the index, middle, ring and little fingers. The subjects were required to remember the sequence of the red spots on the display. After a delay of 14 seconds, the subjects tapped their fingers according to the order of the red spots, as soon as the red spots turned green. After an interval of 14 seconds, another sequence appeared. Every sequence lasted for 28 seconds, including preparation and execution phases. A total of nine sequences per subject were performed. The data were analyzed using deconvolution and cluster methods, and program ＂cluster＂ was used to statistically analyze the coordinate positions of deconvolution and cluster data. MAIN OUTCOME MEASURES： Brain activation maps by deconvolution and brain function maps by clustering of the maximum peak values; blood oxygenation level dependent curves by deconvolution; coordinates of peak values and activation volumes by the two methods. RESULTS： The deconvolution method could not integrate the brain activation maps during different tasks into one activation picture, which made it difficult to identify exactly the spatial distribution of various activities in certain brain areas. Cluster analysis, using maximum peak values, clearly showed brain areas of monofunction and multifunction, even complex function, and presented a clear spatial distribution of multiple functional movements. Using the command ＂clust＂ with the same parameters, the volumes of main brain activation areas were consistent, indicating the maximum peak values are completely reliable in contrast to the deconvolution method. CONCLUSION： Cluster analysis is conducive to the analysis of multifunctional complex areas. Clustering using maximum peak values is a reliable method. Brain areas, such as primary motor cortex, supplementary motor area, and posterior parietal cortex, are not monofunctional areas, but multifunctional, complex ones. The activation maps derived by deconvolution statistics are distributed in many maps, which are not convenient to determine the functional distribution of complex brain areas.
基金the National Natural Science Foundation of China.
文摘On the reasonable hypothesis that the internal motions of member stars of a cluster are random and isotropic, a method which can be used to estimate the velocity distance of the cluster and its uncertainty is developed. The velocity distance so determined is an absolute distance estimate, and is completely independent of the （widely used） luminosity distance, which is a relative distance estimate. Using the published high-accuracy observational data of radial velocities and proper motions of the stars in the open cluster M11 region, we have determined the distance of M 11 to be 1.89 ± 0.52 kpc. This is in quite good agreement with the published luminosity distances of the cluster. We briefly discuss the problems concerned, including the sources of errors in the method and its applicable range.
基金Supported by the National Natural Science Foundation of China(61303127)Project of Science and Technology Department of Sichuan Province(2014SZ0223,2014GZ0100,2015GZ0212)+1 种基金Key Program of Education Department of Sichuan Province(11ZA130,13ZA0169)Postgraduate Innovation Fund Project by Southwest University of Science and Technology(15ycx057)
文摘The key pose frames of a human motion pose sequence,play an important role in the compression,retrieval and semantic analysis of continuous human motion.The current available clustering methods in literatures are difficult to determine the number of key pose frames automatically,and may destroy the postures’ temporal relationships while extracting key frames.To deal with this problem,this paper proposes a new key pose frames extraction method on the basis of 3D space distances of joint points and the improved X-means clustering algorithm.According to the proposed extraction method,the final key pose frame sequence could be obtained by describing the posture of human body with space distance of particular joint points and then the time-constraint X-mean algorithm is applied to cluster and filtrate the posture sequence.The experimental results show that the proposed method can automatically determine the number of key frames and save the temporal characteristics of motion frames according to the motion pose sequence.
文摘为防止船舶违规安装虚假船舶通信系统软件并用其模拟发送干扰船舶自动识别系统(automatic identification system,AIS)的信号,提出一种基于运动特征的双阶段虚假船舶通信系统检测算法(two-stage false ship communication system detection algorithm based on motion features,FSMF)。FSMF算法分析虚假船舶通信系统与AIS同时开启和间隔开启两种干扰情况下的船舶运动轨迹特征,通过计算轨迹之间的时间重叠度将识别过程分为两个阶段。在第一阶段,将动态时间规整(dynamic time warping,DTW)方法应用于时间重叠度为0的轨迹,利用地理距离和动态距离判断轨迹相似性,识别出两者间隔开启时的异常船舶。在第二阶段,将聚类算法应用于时间重叠度大于0的轨迹,把聚成同一簇的轨迹识别为两者同时开启时的运动轨迹,进而识别出异常船舶。通过三种不同类型的数据集对FSMF算法进行性能验证。随机海域的AIS数据分析结果表明,该算法能够有效识别安装虚假船舶通信系统软件的异常船舶,提升船舶监控能力,降低潜在的安全风险。
