In order to obtain a compact and exact representation of 2D range scans,UKF(unscented Kalman filter) and CDKF(central difference Kalman filter) were proposed for extracting the breakpoint of the laser data. Line extra...In order to obtain a compact and exact representation of 2D range scans,UKF(unscented Kalman filter) and CDKF(central difference Kalman filter) were proposed for extracting the breakpoint of the laser data. Line extraction was performed in every continuous breakpoint region by detecting the optimal angle and the optimal distance in polar coordinates,and every breakpoint area was constructed with two points. As a proof to the method,an experiment was performed by a mobile robot equipped with one SICK laser rangefinder,and the results of UKF/CDKF in breakpoint detection and line extraction were compared with those of the EKF(extended Kalman filter) . The results show that the exact geometry of the raw laser data of the environments can be obtained by segmented raw measurements(combining the proposed breakpoint detection approach with the line extraction method) ,and method UKF is the best one compared with CDKF and EKF.展开更多
Digitizing road maps manually is an expensive and time-consuming task. Several methods that intend to develop fully or semi-automated systems have been proposed. In this work we introduce a method, based on the Radon ...Digitizing road maps manually is an expensive and time-consuming task. Several methods that intend to develop fully or semi-automated systems have been proposed. In this work we introduce a method, based on the Radon transform and optimal algorithms, which extracts automatically roads on images of rural areas, images that were acquired by digital cameras and airborne laser scanners. The proposed method detects linear segments iteratively and starting from this it generates the centerlines of the roads. The method is based on an objective function which depends on three parameters related to the correlation between the cross-sections, spectral similarity and directions of the segments. Different tests were performed using aerial photos, Ikonos images and laser scanner data of an area located in the state of Parana （Brazil） and their results are presented and discussed. The quality of the detection of the roads centerlines was computed using several indexes - completeness, correctness and RMS. The values obtained reveal the good performance of the proposed methodology.展开更多
TiC reinforced nickel-based composite coatings with different molybdenum contents were in-situ fabricated on 316L steel by the pulsed Nd:YAG laser in order to solve the severe wear problem of biomass fired boiler tube...TiC reinforced nickel-based composite coatings with different molybdenum contents were in-situ fabricated on 316L steel by the pulsed Nd:YAG laser in order to solve the severe wear problem of biomass fired boiler tubes.TiB 2 decomposed and formed several borides in composite coatings.The microstructure and phase compositions of coatings were analyzed by means of scanning electron microscopy (SEM),energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD).It was found that the increase of molybdenum could create new binder phases and lessen deficiencies in the coatings,preventing the reinforcement from being pulled out of the matrices and leading to less delaminations during erosion.Though the addition of molybdenum improved the average hardness of composites,it could not improve the wear resistance.The wear mechanisms of these composite coatings were further discussed in this paper.展开更多
基金Project(2003AA1Z2130)supported by the National High-Tech Research and Development Program of ChinaProject(2005C11001-02)supported by the Science and Technology Project of Zhejiang Province,China
文摘In order to obtain a compact and exact representation of 2D range scans,UKF(unscented Kalman filter) and CDKF(central difference Kalman filter) were proposed for extracting the breakpoint of the laser data. Line extraction was performed in every continuous breakpoint region by detecting the optimal angle and the optimal distance in polar coordinates,and every breakpoint area was constructed with two points. As a proof to the method,an experiment was performed by a mobile robot equipped with one SICK laser rangefinder,and the results of UKF/CDKF in breakpoint detection and line extraction were compared with those of the EKF(extended Kalman filter) . The results show that the exact geometry of the raw laser data of the environments can be obtained by segmented raw measurements(combining the proposed breakpoint detection approach with the line extraction method) ,and method UKF is the best one compared with CDKF and EKF.
文摘Digitizing road maps manually is an expensive and time-consuming task. Several methods that intend to develop fully or semi-automated systems have been proposed. In this work we introduce a method, based on the Radon transform and optimal algorithms, which extracts automatically roads on images of rural areas, images that were acquired by digital cameras and airborne laser scanners. The proposed method detects linear segments iteratively and starting from this it generates the centerlines of the roads. The method is based on an objective function which depends on three parameters related to the correlation between the cross-sections, spectral similarity and directions of the segments. Different tests were performed using aerial photos, Ikonos images and laser scanner data of an area located in the state of Parana （Brazil） and their results are presented and discussed. The quality of the detection of the roads centerlines was computed using several indexes - completeness, correctness and RMS. The values obtained reveal the good performance of the proposed methodology.
基金supported by the National Science & Technology Pillar Program (Grant No. 2011BEA12B03)the National Natural Science Foundation of China (Grant No. 51101056)+2 种基金the National Basic Research Program of China (Grant No. 2011CB710706)the Fundamental Research Funds for the Central Universities (Grant No. 12MS07)the State Key Laboratory of Advanced Metals and Materials (Grant No. 2010Z-02)
文摘TiC reinforced nickel-based composite coatings with different molybdenum contents were in-situ fabricated on 316L steel by the pulsed Nd:YAG laser in order to solve the severe wear problem of biomass fired boiler tubes.TiB 2 decomposed and formed several borides in composite coatings.The microstructure and phase compositions of coatings were analyzed by means of scanning electron microscopy (SEM),energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD).It was found that the increase of molybdenum could create new binder phases and lessen deficiencies in the coatings,preventing the reinforcement from being pulled out of the matrices and leading to less delaminations during erosion.Though the addition of molybdenum improved the average hardness of composites,it could not improve the wear resistance.The wear mechanisms of these composite coatings were further discussed in this paper.
