In this paper, a clustering algorithm is proposed based on the high correlation among the overlapped field of views for the wireless multimedia sensor networks. Firstly, by calculating the area of the overlapped field...In this paper, a clustering algorithm is proposed based on the high correlation among the overlapped field of views for the wireless multimedia sensor networks. Firstly, by calculating the area of the overlapped field of views （FoVs） based on the gird method, node correlations have been obtained. Then, the algorithm utilizes the node correlations to partition the network region in which there are high correlation multimedia sensor nodes. Meanwhile, in order to minimize the energy consumption for transmitting images, the strategy of the cluster heads election is proposed based on the cost estimation, which consists of signal strength and residual energy as well as the node correlation. Simulation results show that the proposed algorithm can balance the energy consumption and extend the network lifetime effectively.展开更多
Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outsi...Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.展开更多
针对基于武器平台的体系对抗综合仿真系统中通信连通性功能的实际需求,给出了通信连通性模块的组成、功能及仿真流程,对其中的关键模型进行了分析研究,重点阐述了路径损耗计算和视野(FOV,Field Of View)判断模型。结合实例进行了仿真实...针对基于武器平台的体系对抗综合仿真系统中通信连通性功能的实际需求,给出了通信连通性模块的组成、功能及仿真流程,对其中的关键模型进行了分析研究,重点阐述了路径损耗计算和视野(FOV,Field Of View)判断模型。结合实例进行了仿真实验,仿真结果充分验证了模型和方法的有效性。通信连通性模块的研究开发为体系对抗仿真系统的实现奠定了基础,也可为电子信息系统及装备分析研究、研制与试验评估以及建模仿真等提供参考。展开更多
研究了一种多摄像机的视野(Field of View,FOV)分界线恢复方法,利用Harris角点检测和单应矩阵的方法完成摄像机视野分界线恢复。用Harris角点检测算法提取图像中角点特征;在有重叠区域图像间进行特征点匹配,再根据匹配点计算图像间的单...研究了一种多摄像机的视野(Field of View,FOV)分界线恢复方法,利用Harris角点检测和单应矩阵的方法完成摄像机视野分界线恢复。用Harris角点检测算法提取图像中角点特征;在有重叠区域图像间进行特征点匹配,再根据匹配点计算图像间的单应矩阵;最后由图像的边界点及图像间的单应矩阵计算摄像机的FOV分界线。该方法能准确恢复摄像机的视野分界线,具有准确性和鲁棒性。展开更多
In this paper, a new adaptive optimal guidance law with impact angle and seeker’s field-of-view(FOV) angle constraints is proposed. To this end, the generalized optimal guidance law is derived first. A changeable imp...In this paper, a new adaptive optimal guidance law with impact angle and seeker’s field-of-view(FOV) angle constraints is proposed. To this end, the generalized optimal guidance law is derived first. A changeable impact angle weighting(IAW) coefficient is introduced and used to modify the guidance law to make it adaptive for all guidance constraints. After integrating the closed-form solution of the guidance command with linearized engagement kinematics, the analytic predictive models of impact angle and FOV angle are built, and the available range of IAW corresponding to constraints is certain. Next, a calculation scheme is presented to acquire the real-time value of IAW during the entire guidance process. When applying the proposed guidance law, the IAW will keep small to avoid a trajectory climbing up to limit FOV angle at an initial time but will increase with the closing target to improve impact position and angle accuracy, thereby ensuring that the guidance law can juggle orders of guidance accuracy and constraints control.展开更多
In this paper, a trajectory shaping guidance law,which considers constraints of field-of-view(FOV) angle, impact angle, and terminal lateral acceleration, is proposed for a constant speed missile against a stationary ...In this paper, a trajectory shaping guidance law,which considers constraints of field-of-view(FOV) angle, impact angle, and terminal lateral acceleration, is proposed for a constant speed missile against a stationary target. First, to decouple constraints of the FOV angle and the terminal lateral acceleration, the third-order polynomial with respect to the line-ofsight(LOS) angle is introduced. Based on an analysis of the relationship between the looking angle and the guidance coefficient,the boundary of the coefficient that satisfies the FOV constraint is obtained. The terminal guidance law coefficient is used to guarantee the convergence of the terminal conditions. Furthermore, the proposed law can be implemented under bearingsonly information, as the guidance command does not involve the relative range and the LOS angle rate. Finally, numerical simulations are performed based on a kinematic vehicle model to verify the effectiveness of the guidance law. Overall, the work offers an easily implementable guidance law with closed-form guidance gains, which is suitable for engineering applications.展开更多
基金supported by the National Natural Science Foundation of China (60973139, 61170065, 61171053, 61003039, 61003236, 61103195)the Natural Science Foundation of Jiangsu Province (BK2011755)+10 种基金Scientific & Technological Support Project (Industry) of Jiangsu Province (BE2010197,BE2010198, BE2011844, BE2011189)Natural Science Key Fund for Colleges and Universities in Jiangsu Province (11KJA520001)the Jiangsu Provincial Research Scheme of Natural Science for Higher Education Institutions(10KJB520013, 11KJB520014,11KJB520016)Scientific Research & Industry Promotion Project for Higher Education Institutions(JH2010-14, JHB2011-9)Postdoctoral Foundation (20100480048)Science & Technology Innovation Fund for higher education institutions of Jiangsu Province (CX10B-196Z,CX10B-200Z,CXZZ11-0405, CXZZ11-0406, CXZZ11_0409)Doctoral Fund of Ministry of Education of China(20103223120007, 20113223110002)key Laboratory Foundation of Information Technology processing of Jiangsu Province (KJS1022)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD),(K93-9-2010-13)the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions (yx002001)Research Fund of Jiangsu Suqian College (2012ky17)
文摘In this paper, a clustering algorithm is proposed based on the high correlation among the overlapped field of views for the wireless multimedia sensor networks. Firstly, by calculating the area of the overlapped field of views （FoVs） based on the gird method, node correlations have been obtained. Then, the algorithm utilizes the node correlations to partition the network region in which there are high correlation multimedia sensor nodes. Meanwhile, in order to minimize the energy consumption for transmitting images, the strategy of the cluster heads election is proposed based on the cost estimation, which consists of signal strength and residual energy as well as the node correlation. Simulation results show that the proposed algorithm can balance the energy consumption and extend the network lifetime effectively.
基金supported by the Tehran University of Medical Sciences under Grant No.36291PET/CT and Cyclotron Center of Masih Daneshvari Hospital at Shahid Beheshti University of Medical Sciences。
文摘Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.
文摘针对基于武器平台的体系对抗综合仿真系统中通信连通性功能的实际需求,给出了通信连通性模块的组成、功能及仿真流程,对其中的关键模型进行了分析研究,重点阐述了路径损耗计算和视野(FOV,Field Of View)判断模型。结合实例进行了仿真实验,仿真结果充分验证了模型和方法的有效性。通信连通性模块的研究开发为体系对抗仿真系统的实现奠定了基础,也可为电子信息系统及装备分析研究、研制与试验评估以及建模仿真等提供参考。
文摘研究了一种多摄像机的视野(Field of View,FOV)分界线恢复方法,利用Harris角点检测和单应矩阵的方法完成摄像机视野分界线恢复。用Harris角点检测算法提取图像中角点特征;在有重叠区域图像间进行特征点匹配,再根据匹配点计算图像间的单应矩阵;最后由图像的边界点及图像间的单应矩阵计算摄像机的FOV分界线。该方法能准确恢复摄像机的视野分界线,具有准确性和鲁棒性。
文摘运动目标正确交接是多摄像机视频监控中的关键,视野分界线是解决目标交接的有效工具。不需标定摄像机参数,提出了一种利用尺度不变特征变换(SIFT:scale-invariant freatures transform)及射影变换实现目标交接的算法。首先使用SIFT算法在不同视角拍摄的图像间自动生成匹配的特征点,由空间共面的特征点及其相应匹配点生成图像间的单应变换矩阵。然后由图像边界点及单应矩阵计算摄像机视野(FOV:field of view)分界线。最后利用目标位置信息及射影变换实现目标正确交接。实验结果表明本文的方法具有有效性和鲁棒性。
基金supported by the Aeronautical Science Foundation of China(20150172001)
文摘In this paper, a new adaptive optimal guidance law with impact angle and seeker’s field-of-view(FOV) angle constraints is proposed. To this end, the generalized optimal guidance law is derived first. A changeable impact angle weighting(IAW) coefficient is introduced and used to modify the guidance law to make it adaptive for all guidance constraints. After integrating the closed-form solution of the guidance command with linearized engagement kinematics, the analytic predictive models of impact angle and FOV angle are built, and the available range of IAW corresponding to constraints is certain. Next, a calculation scheme is presented to acquire the real-time value of IAW during the entire guidance process. When applying the proposed guidance law, the IAW will keep small to avoid a trajectory climbing up to limit FOV angle at an initial time but will increase with the closing target to improve impact position and angle accuracy, thereby ensuring that the guidance law can juggle orders of guidance accuracy and constraints control.
基金supported by the Defense Science and Technology Key Laboratory Fund of Luoyang Electro-Optical Equipment Institute,Aviation Industry Corporation of China (6142504200108)。
文摘In this paper, a trajectory shaping guidance law,which considers constraints of field-of-view(FOV) angle, impact angle, and terminal lateral acceleration, is proposed for a constant speed missile against a stationary target. First, to decouple constraints of the FOV angle and the terminal lateral acceleration, the third-order polynomial with respect to the line-ofsight(LOS) angle is introduced. Based on an analysis of the relationship between the looking angle and the guidance coefficient,the boundary of the coefficient that satisfies the FOV constraint is obtained. The terminal guidance law coefficient is used to guarantee the convergence of the terminal conditions. Furthermore, the proposed law can be implemented under bearingsonly information, as the guidance command does not involve the relative range and the LOS angle rate. Finally, numerical simulations are performed based on a kinematic vehicle model to verify the effectiveness of the guidance law. Overall, the work offers an easily implementable guidance law with closed-form guidance gains, which is suitable for engineering applications.
