Camera calibration is critical in computer vision measurement system, affecting the accuracy of the whole system. Many camera calibration methods have been proposed, but they cannot consider precision and operation co...Camera calibration is critical in computer vision measurement system, affecting the accuracy of the whole system. Many camera calibration methods have been proposed, but they cannot consider precision and operation complexity at the same time. In this paper, a new technique is proposed to calibrate camera. Firstly, the global calibration method is described in de-tail. It requires the camera to observe a checkerboard pattern shown at a few different orientations. The checkerboard corners are obtained by Harris algorithm. With direct linear transformation and non-linear optimal algorithm, the global calibration pa-rameters are obtained. Then, a sub-regional method is proposed. Those corners are divided into two groups, middle corners and edge corners, which are used to calibrate the corresponding area to get two sets of calibration parameters. Finally, some experimental images are used to test the proposed method. Experimental results demonstrate that the average projection error of sub-region method is decreased at least 16% compared with the global calibration method. The proposed technique is simple and accurate. It is suitable for the industrial computer vision measurement.展开更多
In order to solve the in-situ measurement problem of workpiece with complex structures,a cantilever coordinate measuring machine(CCMM)is proposed to adapt to the finite space constraints of the 5-axis computer numeric...In order to solve the in-situ measurement problem of workpiece with complex structures,a cantilever coordinate measuring machine(CCMM)is proposed to adapt to the finite space constraints of the 5-axis computer numerical control(CNC)processing site.Structure design of dense ball bearing shafting is analyzed and optimized.Factors affecting measurement accuracy of CCMM are analyzed,and measurement accuracy is validated by experiments.Results show that the structure of CCMM is able to satisfy requirements of technical specification,and the in-situ measurement of blisk manufacturing is realized.The CCMM developed is of important significance for machining quantity improvement of blisk and development of large aircraft production.展开更多
Leaf discs of five cultivars of sugarcane exhibiting different degree of susceptibility to leaf scald were used to measure β-1,3 glucanase activity before and after experimental infection with Xanthomonas albilineans...Leaf discs of five cultivars of sugarcane exhibiting different degree of susceptibility to leaf scald were used to measure β-1,3 glucanase activity before and after experimental infection with Xanthomonas albilineans. Leaf discs were permeabilized with iso-propanol to facilitate the uptake of the enzyme substrate by intact tissues and to improve the enzyme assay. Bacterial infection significantly enhances β-1,3 glucanase activity of sensitive cultivars whereas significantly decreased that of the resistant one. Low concentrations of salicylate increase the hydrolase activity whereas jasmonic acid do not act as an elicitor of the enzyme and β-1,3 glucanase, such as laminarin, significantly inhibits the production of β-1,3 glucanase. Thus, the enzyme must be considered as a sensitivity factor induced by the pathogen.展开更多
Introduction: The aim of this study is to describe the normal variability of the optic disc morphology by warping method, and the estimation of a lot of quantitative and qualitative parameters that characterizes the h...Introduction: The aim of this study is to describe the normal variability of the optic disc morphology by warping method, and the estimation of a lot of quantitative and qualitative parameters that characterizes the healthy human optic disc. Methods: There have been analyzed 251 stereo-color photos acquired through ophtalmoscopic exam with a Zeiss retinophot, on healthy eyes,展开更多
基金Tianjin Research Program of Application Foundation and Advanced Technology(No.14JCYBJC18600,No.14JCZDJC39700)the National Key Scientific Instrument and Equipment Development Project(No.2013YQ17053903)
文摘Camera calibration is critical in computer vision measurement system, affecting the accuracy of the whole system. Many camera calibration methods have been proposed, but they cannot consider precision and operation complexity at the same time. In this paper, a new technique is proposed to calibrate camera. Firstly, the global calibration method is described in de-tail. It requires the camera to observe a checkerboard pattern shown at a few different orientations. The checkerboard corners are obtained by Harris algorithm. With direct linear transformation and non-linear optimal algorithm, the global calibration pa-rameters are obtained. Then, a sub-regional method is proposed. Those corners are divided into two groups, middle corners and edge corners, which are used to calibrate the corresponding area to get two sets of calibration parameters. Finally, some experimental images are used to test the proposed method. Experimental results demonstrate that the average projection error of sub-region method is decreased at least 16% compared with the global calibration method. The proposed technique is simple and accurate. It is suitable for the industrial computer vision measurement.
基金National Natural Science Foundation of China(No.51375338)
文摘In order to solve the in-situ measurement problem of workpiece with complex structures,a cantilever coordinate measuring machine(CCMM)is proposed to adapt to the finite space constraints of the 5-axis computer numerical control(CNC)processing site.Structure design of dense ball bearing shafting is analyzed and optimized.Factors affecting measurement accuracy of CCMM are analyzed,and measurement accuracy is validated by experiments.Results show that the structure of CCMM is able to satisfy requirements of technical specification,and the in-situ measurement of blisk manufacturing is realized.The CCMM developed is of important significance for machining quantity improvement of blisk and development of large aircraft production.
文摘Leaf discs of five cultivars of sugarcane exhibiting different degree of susceptibility to leaf scald were used to measure β-1,3 glucanase activity before and after experimental infection with Xanthomonas albilineans. Leaf discs were permeabilized with iso-propanol to facilitate the uptake of the enzyme substrate by intact tissues and to improve the enzyme assay. Bacterial infection significantly enhances β-1,3 glucanase activity of sensitive cultivars whereas significantly decreased that of the resistant one. Low concentrations of salicylate increase the hydrolase activity whereas jasmonic acid do not act as an elicitor of the enzyme and β-1,3 glucanase, such as laminarin, significantly inhibits the production of β-1,3 glucanase. Thus, the enzyme must be considered as a sensitivity factor induced by the pathogen.
文摘Introduction: The aim of this study is to describe the normal variability of the optic disc morphology by warping method, and the estimation of a lot of quantitative and qualitative parameters that characterizes the healthy human optic disc. Methods: There have been analyzed 251 stereo-color photos acquired through ophtalmoscopic exam with a Zeiss retinophot, on healthy eyes,
