The autonomous "celestial navigation scheme" for deep space probe departing from the earth and the autonomous "optical navigation scheme" for encountering object celestial body are presented. Then,...The autonomous "celestial navigation scheme" for deep space probe departing from the earth and the autonomous "optical navigation scheme" for encountering object celestial body are presented. Then, aiming at the conditions that large initial estimation errors and non-Gaussian distribution of state or measurement errors may exist in orbit determination process of the two phases, UPF (unscented particle filter) is introduced into the navigation schemes. By tackling nonlinear and non-Gaussian problems, UPF overcomes the accuracy influence brought by the traditional EKF (extended Kalman filter), UKF (unscented Kalman filter), and PF (particle filter) schemes in approximate treatment to nonlinear and non-Gaussian state model and measurement model. The numerical simulations demonstrate the feasibility and higher accuracy of the UPF navigation scheme.展开更多
PM10 samples of 62 Quartz filters and 75 PTFE filters from 28 Jul. 1999 to 10 Jan. 2000 in London were collected and analyzed. The difference between Quartz filter and PTFE filter in monitoring PM10 and anion ion conc...PM10 samples of 62 Quartz filters and 75 PTFE filters from 28 Jul. 1999 to 10 Jan. 2000 in London were collected and analyzed. The difference between Quartz filter and PTFE filter in monitoring PM10 and anion ion concentration has been studied. The mean PM10, SO42- concentrations of Quartz filters were higher than those of PTFT filters, which had statistically significant （P〈0.05）. The mean PM 10 concentration of Quartz filter was almost 1.5 times of that of PTFE filter. However, there were no statistically significant among CI, NO3-, PO43 comparison of the two kinds filters （P〉0.05）. We should be careful when selecting filter to do research about PM10 and anion ion concentration.展开更多
We propose an algorithm of embedding ensemble tracking in a stochastic framework to achieve robust tracking performance under partial occlusion,illumination changes,and abrupt motion.It operates on likelihood images g...We propose an algorithm of embedding ensemble tracking in a stochastic framework to achieve robust tracking performance under partial occlusion,illumination changes,and abrupt motion.It operates on likelihood images generated by the ensemble method,and combines mean shift and particle filtering in a principled way,where a better proposal distribution is de-signed by first propagating particles via a motion model,and then running mean shift to move towards their local peaks in the likelihood image.An observation model in the particle filter incorporates global and local information within a region,and an adaptive motion model is adopted to depict the evolution of the object state.The algorithm needs fewer particles to manage the tracking task compared with the general particle filter,and recaptures the object quickly after occlusion occurs.Experiments on two image sequences demonstrate the effectiveness and robustness of the proposed algorithm.展开更多
基金the National "863" High Technology Development Project of China (2005AA735080).
文摘The autonomous "celestial navigation scheme" for deep space probe departing from the earth and the autonomous "optical navigation scheme" for encountering object celestial body are presented. Then, aiming at the conditions that large initial estimation errors and non-Gaussian distribution of state or measurement errors may exist in orbit determination process of the two phases, UPF (unscented particle filter) is introduced into the navigation schemes. By tackling nonlinear and non-Gaussian problems, UPF overcomes the accuracy influence brought by the traditional EKF (extended Kalman filter), UKF (unscented Kalman filter), and PF (particle filter) schemes in approximate treatment to nonlinear and non-Gaussian state model and measurement model. The numerical simulations demonstrate the feasibility and higher accuracy of the UPF navigation scheme.
文摘PM10 samples of 62 Quartz filters and 75 PTFE filters from 28 Jul. 1999 to 10 Jan. 2000 in London were collected and analyzed. The difference between Quartz filter and PTFE filter in monitoring PM10 and anion ion concentration has been studied. The mean PM10, SO42- concentrations of Quartz filters were higher than those of PTFT filters, which had statistically significant （P〈0.05）. The mean PM 10 concentration of Quartz filter was almost 1.5 times of that of PTFE filter. However, there were no statistically significant among CI, NO3-, PO43 comparison of the two kinds filters （P〉0.05）. We should be careful when selecting filter to do research about PM10 and anion ion concentration.
基金Project(No.2006AA10Z204)supported by the National High-Tech Research and Development Program(863) of China
文摘We propose an algorithm of embedding ensemble tracking in a stochastic framework to achieve robust tracking performance under partial occlusion,illumination changes,and abrupt motion.It operates on likelihood images generated by the ensemble method,and combines mean shift and particle filtering in a principled way,where a better proposal distribution is de-signed by first propagating particles via a motion model,and then running mean shift to move towards their local peaks in the likelihood image.An observation model in the particle filter incorporates global and local information within a region,and an adaptive motion model is adopted to depict the evolution of the object state.The algorithm needs fewer particles to manage the tracking task compared with the general particle filter,and recaptures the object quickly after occlusion occurs.Experiments on two image sequences demonstrate the effectiveness and robustness of the proposed algorithm.
