The concept of virtual manufacturing and measuring cell (VMMC) is proposed, the systematic architecture of the VMMC is established and two key problems: the error fusion in machining and the reconstructable modeling o...The concept of virtual manufacturing and measuring cell (VMMC) is proposed, the systematic architecture of the VMMC is established and two key problems: the error fusion in machining and the reconstructable modeling of workpiece during virtual manufacturing and measuring, are discussed. An actual VMMC is presented as an example and its modularized frame is introduced.展开更多
This paper sums up four security factors after analyzing co-residency threats caused by the special multitenant environment in the cloud.To secure the factors,a multiway dynamic trust chain transfer model was proposed...This paper sums up four security factors after analyzing co-residency threats caused by the special multitenant environment in the cloud.To secure the factors,a multiway dynamic trust chain transfer model was proposed on the basis of a measurement interactive virtual machine and current behavior to protect the integrity of the system.A trust chain construction module is designed in a virtual machine monitor.Through dynamic monitoring,it achieves the purpose of transferring integrity between virtual machine.A cloud system with a trust authentication function is implemented on the basis of the model,and its practicability is shown.展开更多
Compared with conventional multiple-input multiple-output(MIMO),massive MIMO system with tens or even hundreds of antennas is able to give better performance in capacity and spectral efficiency,which is a promising te...Compared with conventional multiple-input multiple-output(MIMO),massive MIMO system with tens or even hundreds of antennas is able to give better performance in capacity and spectral efficiency,which is a promising technology for 5G.Considering this,massive MIMO has become a hot research topic all over the world.In this paper,the channel measurements and models of massive MIMO in recent years are summarized.Besides,the related 256 antenna elements with 200 MHz bandwidth at 3.5 GHz proposed by our team,the verification of rationality of the measurement method,and the spatial evolution of clusters in mobile scenario are provided.展开更多
A novel virtual four-ocular stereo measurement system based on single high speed camera is proposed for measuring double beating wings of a high speed flapping insect. The principle of virtual monocular system consist...A novel virtual four-ocular stereo measurement system based on single high speed camera is proposed for measuring double beating wings of a high speed flapping insect. The principle of virtual monocular system consisting of a few planar mirrors and a single high speed camera is introduced. The stereo vision measurement principle based on optic triangulation is explained. The wing kinematics parameters are measured. Results show that this virtual stereo system not only decreases system cost extremely but also is effective to insect motion measurement.展开更多
Geometric error is the main factor affecting the machining accuracy of hybrid machine tools.Kinematic calibration is an effective way to improve the geometric accuracy of hybrid machine tools.The necessity to measure ...Geometric error is the main factor affecting the machining accuracy of hybrid machine tools.Kinematic calibration is an effective way to improve the geometric accuracy of hybrid machine tools.The necessity to measure both position and orientation at each pose,as well as the instability of identification in case of incomplete measurements,severely affects the application of traditional calibration methods.In this study,a kinematic calibration method with high measurement efficiency and robust identification is proposed to improve the kinematic accuracy of a five-axis hybrid machine tool.First,the configuration is introduced,and an error model is derived.Further,by investigating the mechanism error characteristics,a measurement scheme that only requires tool centre point position error measurement and one alignment operation is proposed.Subsequently,by analysing the effects of unmeasured degrees of freedom(DOFs)on other DOFs,an improved nonlinear least squares method based on virtual measurement values is proposed to achieve stable parameter identification in case of incomplete measurement,without introducing additional parameters.Finally,the proposed calibration method is verified through simulations and experiments.The proposed method can efficiently accomplish the kinematic calibration of the hybrid machine tool.The accuracy of the hybrid machine tool is significantly improved after calibration,satisfying actual aerospace machining requirements.展开更多
文摘The concept of virtual manufacturing and measuring cell (VMMC) is proposed, the systematic architecture of the VMMC is established and two key problems: the error fusion in machining and the reconstructable modeling of workpiece during virtual manufacturing and measuring, are discussed. An actual VMMC is presented as an example and its modularized frame is introduced.
基金supported by The National Natural Science Foundation for Young Scientists of China under Grant No.61303263the Jiangsu Provincial Research Foundation for Basic Research(Natural Science Foundation)under Grant No.BK20150201+4 种基金the Scientific Research Key Project of Beijing Municipal Commission of Education under Grant No.KZ201210015015Project Supported by the National Natural Science Foundation of China(Grant No.61370140)the Scientific Research Common Program of the Beijing Municipal Commission of Education(Grant No.KMKM201410015006)The National Science Foundation of China under Grant Nos.61232016 and U1405254and the PAPD fund
文摘This paper sums up four security factors after analyzing co-residency threats caused by the special multitenant environment in the cloud.To secure the factors,a multiway dynamic trust chain transfer model was proposed on the basis of a measurement interactive virtual machine and current behavior to protect the integrity of the system.A trust chain construction module is designed in a virtual machine monitor.Through dynamic monitoring,it achieves the purpose of transferring integrity between virtual machine.A cloud system with a trust authentication function is implemented on the basis of the model,and its practicability is shown.
基金supported in part by National Natural Science Foundation of China(61322110,6141101115)in part by National Science and Technology Major Project of the Ministry of Science and Technology(2015ZX03002008)+2 种基金in part by National Key Technology Research and Development Program(2012BAF14B01)“863”Program(2015AA01A703)Doctoral Fund of Ministry of Education(201300051100013).
文摘Compared with conventional multiple-input multiple-output(MIMO),massive MIMO system with tens or even hundreds of antennas is able to give better performance in capacity and spectral efficiency,which is a promising technology for 5G.Considering this,massive MIMO has become a hot research topic all over the world.In this paper,the channel measurements and models of massive MIMO in recent years are summarized.Besides,the related 256 antenna elements with 200 MHz bandwidth at 3.5 GHz proposed by our team,the verification of rationality of the measurement method,and the spatial evolution of clusters in mobile scenario are provided.
基金The work was supported by the National Science Fund for Distinguished Young Scholars of China under Grant No. 50125518.
文摘A novel virtual four-ocular stereo measurement system based on single high speed camera is proposed for measuring double beating wings of a high speed flapping insect. The principle of virtual monocular system consisting of a few planar mirrors and a single high speed camera is introduced. The stereo vision measurement principle based on optic triangulation is explained. The wing kinematics parameters are measured. Results show that this virtual stereo system not only decreases system cost extremely but also is effective to insect motion measurement.
基金supported by the National Natural Science Foundation of China(Nos.52275442 and 51975319)。
文摘Geometric error is the main factor affecting the machining accuracy of hybrid machine tools.Kinematic calibration is an effective way to improve the geometric accuracy of hybrid machine tools.The necessity to measure both position and orientation at each pose,as well as the instability of identification in case of incomplete measurements,severely affects the application of traditional calibration methods.In this study,a kinematic calibration method with high measurement efficiency and robust identification is proposed to improve the kinematic accuracy of a five-axis hybrid machine tool.First,the configuration is introduced,and an error model is derived.Further,by investigating the mechanism error characteristics,a measurement scheme that only requires tool centre point position error measurement and one alignment operation is proposed.Subsequently,by analysing the effects of unmeasured degrees of freedom(DOFs)on other DOFs,an improved nonlinear least squares method based on virtual measurement values is proposed to achieve stable parameter identification in case of incomplete measurement,without introducing additional parameters.Finally,the proposed calibration method is verified through simulations and experiments.The proposed method can efficiently accomplish the kinematic calibration of the hybrid machine tool.The accuracy of the hybrid machine tool is significantly improved after calibration,satisfying actual aerospace machining requirements.
