Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames. Performances of three methods of coordinate rotation： double rotation （DR...Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames. Performances of three methods of coordinate rotation： double rotation （DR）, triple rotation （TR）, and classic planar-fit rotation （PF） were examined in terms of correction of eddy covariance flux. Using the commonly used DR and TR methods, unreasonable rotation angles are encountered at low wind speeds and cause significant run-to-run errors of some turbulence characteristics. The PF method rotates the coordinate system to an ensemble-averaged plane, and shows large tilt error due to an inaccurate fit plane over variable terrain slopes. In this paper, we propose another coordinate rotation scheme. The observational data were separated into two groups according to wind direction. The PF method was adapted to find an ensemble-averaged streamline plane for each group of hourly runs with wind speed exceeding 1.0 m s-1. Then, the coordinate systems were rotated to their respective best- fit planes for all available hourly observations. We call this the PF10 method. The implications of tilt corrections for the turbulence characteristics are discussed with a focus on integral turbulence characteristics, the spectra of wind-velocity components, and sensible heat and momentum fluxes under various atmospheric stabilities. Our results show that the adapted application of PF provides greatly improved estimates of integral turbulence characteristics in complex terrain and maintains data quality. The comparisons of the sensible heat fluxes for four coordinate rotation methods to fluxes before correction indicate that the PF10 scheme is the best to preserve consistency between fluxes.展开更多
In this paper, the edge detection for a medical image is performed based on Sobel operator, and the bounding box is obtained, by which the effective medical sub-image is extracted. Then, the centroid and the normalize...In this paper, the edge detection for a medical image is performed based on Sobel operator, and the bounding box is obtained, by which the effective medical sub-image is extracted. Then, the centroid and the normalized central moments of the medical sub-image are calculated, and the rotation angle a is obtained by minimizing the second-order central moment based on its rotation invariance. Finally, the whole medical image is rotated around the centroid by --a to correct the tilted image. F^rthermore, inspired by the uniformity degree of the image, the rotation angle ct is revised, which achieves a better correction effect and performance. The experimental results show that the proposed algorithms are fairly reliable and accurate for the determination of tilt angles, and are practical and effective tilt correction techniques.展开更多
The shortage of current different approaches of the vehicle license plate(VLP) tilt correction is analyzed in the paper and a new rotary correction method put forward based on the former ways of the VLP tilt correctio...The shortage of current different approaches of the vehicle license plate(VLP) tilt correction is analyzed in the paper and a new rotary correction method put forward based on the former ways of the VLP tilt correction in the horizontal direction and the vertical direction Owing to the VLP tilt taking place in the vertical direction,the array of the image’s pixels of the same column is broken,and even different rows come into being superposition.The VLP tilt taking place in the horizontal direction,by which the array of the image’s pixels of the same row broken,and so much as different columns come into being superposition.展开更多
In the course of vehicle license plate （VLP） automatic recognition, tilt correction is a very crucial process. According to Karhunen-Loeve （K-L） transformation, the coordinates of characters in the image are arran...In the course of vehicle license plate （VLP） automatic recognition, tilt correction is a very crucial process. According to Karhunen-Loeve （K-L） transformation, the coordinates of characters in the image are arranged into a two-dimensional covariance matrix, on the basis of which the centered process is carried out. Then, the eigenvector and the rotation angle α are computed in turn. The whole image is rotated by -α. Thus, image horizontal tilt correction is performed. In the vertical tilt correction process, three correction methods, which are K-L transformation method, the line fitting method based on K -means clustering （LFMBKC）, and the line fitting based on least squares （LFMBLS）, are put forward to compute the vertical tilt angle θ. After shear transformation （ST） is imposed on the rotated image, the final correction image is obtained. The experimental results verify that this proposed method can be easily implemented, and can quickly and accurately get the tilt angle. It provides a new effective way for the VLP image tilt correction as well.展开更多
In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By com...In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By comparing with the result of a rotary-table tilt test, we concluded that the noises in the acceleration records were caused by ground tilt as a result of rotational ground motion. We analyzed the key noises that may cause baseline offset, and proposed a baseline-correction scheme for preserving the long-period ground motion in accordance with specific pulse positions. We then applied this correction method to some near-field strongmotion acceleration records. The result shows that this method can obtain near-field ground displacements, including permanent displacements, in agreement with GPS data, and that this method is more stable than other methods.展开更多
针对鸟巢、导地线、防震锤和导地线线夹多目标干扰而导致间隔棒倾斜缺陷识别易出现错检、漏检等问题,提出一种电网线路间隔棒倾斜缺陷识别方法。构建激光雷达成像模型来校正电网线路图像;采用黑、白高帽变换来区分图像潜在的黯淡、明亮...针对鸟巢、导地线、防震锤和导地线线夹多目标干扰而导致间隔棒倾斜缺陷识别易出现错检、漏检等问题,提出一种电网线路间隔棒倾斜缺陷识别方法。构建激光雷达成像模型来校正电网线路图像;采用黑、白高帽变换来区分图像潜在的黯淡、明亮区域,并输入到所设计的空间关注分类模型中,确定每个集群的最小超球体半径;根据状态判别方程,去除干扰,完成多目标干扰下的电网线路间隔棒倾斜缺陷识别。经实验验证:所提方法的平均精度均值保持在0.85以上,测试时间为600 s时的帧率(frame per second,FPS)为48.6 f/s;在间隔棒倾斜的状态下,所提方法缺陷识别的平均正确率为95.18%,平均召回率为86.37%,平均F1分数为0.90,表明所提方法不存在错检、漏检,且计算效率高、缺陷识别精度高,适用于各种环境下的电网线路间隔棒倾斜缺陷识别。展开更多
基金supported by the National High Technology Research and Development Program of China(Grant No.2007AA022201)the National Special Fund for Water(Grant No.2008ZX07103007)+1 种基金the National Basic Research Program of China (Grant Nos.2010CB428503 and 2011CB403406)the National Natural Science Foundation of China(Grant Nos. 40805006 and 41075012)
文摘Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames. Performances of three methods of coordinate rotation： double rotation （DR）, triple rotation （TR）, and classic planar-fit rotation （PF） were examined in terms of correction of eddy covariance flux. Using the commonly used DR and TR methods, unreasonable rotation angles are encountered at low wind speeds and cause significant run-to-run errors of some turbulence characteristics. The PF method rotates the coordinate system to an ensemble-averaged plane, and shows large tilt error due to an inaccurate fit plane over variable terrain slopes. In this paper, we propose another coordinate rotation scheme. The observational data were separated into two groups according to wind direction. The PF method was adapted to find an ensemble-averaged streamline plane for each group of hourly runs with wind speed exceeding 1.0 m s-1. Then, the coordinate systems were rotated to their respective best- fit planes for all available hourly observations. We call this the PF10 method. The implications of tilt corrections for the turbulence characteristics are discussed with a focus on integral turbulence characteristics, the spectra of wind-velocity components, and sensible heat and momentum fluxes under various atmospheric stabilities. Our results show that the adapted application of PF provides greatly improved estimates of integral turbulence characteristics in complex terrain and maintains data quality. The comparisons of the sensible heat fluxes for four coordinate rotation methods to fluxes before correction indicate that the PF10 scheme is the best to preserve consistency between fluxes.
基金supported by Foundation of 11th Five-year Plan for Key Construction Academic Subject (Optics) of Hunan Province,PRCScientific Research Fund of Hunan Provincial Education Department, PRC (No. 06C581)
文摘In this paper, the edge detection for a medical image is performed based on Sobel operator, and the bounding box is obtained, by which the effective medical sub-image is extracted. Then, the centroid and the normalized central moments of the medical sub-image are calculated, and the rotation angle a is obtained by minimizing the second-order central moment based on its rotation invariance. Finally, the whole medical image is rotated around the centroid by --a to correct the tilted image. F^rthermore, inspired by the uniformity degree of the image, the rotation angle ct is revised, which achieves a better correction effect and performance. The experimental results show that the proposed algorithms are fairly reliable and accurate for the determination of tilt angles, and are practical and effective tilt correction techniques.
文摘The shortage of current different approaches of the vehicle license plate(VLP) tilt correction is analyzed in the paper and a new rotary correction method put forward based on the former ways of the VLP tilt correction in the horizontal direction and the vertical direction Owing to the VLP tilt taking place in the vertical direction,the array of the image’s pixels of the same column is broken,and even different rows come into being superposition.The VLP tilt taking place in the horizontal direction,by which the array of the image’s pixels of the same row broken,and so much as different columns come into being superposition.
基金supported by Scientific Research Fund of Hunan Province, PRC (No. 07JJ6141)Scientific Research Fund of Hunan Provincial Education Department, PRC (No. 06C582)
文摘In the course of vehicle license plate （VLP） automatic recognition, tilt correction is a very crucial process. According to Karhunen-Loeve （K-L） transformation, the coordinates of characters in the image are arranged into a two-dimensional covariance matrix, on the basis of which the centered process is carried out. Then, the eigenvector and the rotation angle α are computed in turn. The whole image is rotated by -α. Thus, image horizontal tilt correction is performed. In the vertical tilt correction process, three correction methods, which are K-L transformation method, the line fitting method based on K -means clustering （LFMBKC）, and the line fitting based on least squares （LFMBLS）, are put forward to compute the vertical tilt angle θ. After shear transformation （ST） is imposed on the rotated image, the final correction image is obtained. The experimental results verify that this proposed method can be easily implemented, and can quickly and accurately get the tilt angle. It provides a new effective way for the VLP image tilt correction as well.
基金supported by the National Natural Science Foundation of China (41004020)the Director Foundation of Institute of Seismology,China Earthquake Administration (IS200926044)
文摘In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By comparing with the result of a rotary-table tilt test, we concluded that the noises in the acceleration records were caused by ground tilt as a result of rotational ground motion. We analyzed the key noises that may cause baseline offset, and proposed a baseline-correction scheme for preserving the long-period ground motion in accordance with specific pulse positions. We then applied this correction method to some near-field strongmotion acceleration records. The result shows that this method can obtain near-field ground displacements, including permanent displacements, in agreement with GPS data, and that this method is more stable than other methods.
文摘针对鸟巢、导地线、防震锤和导地线线夹多目标干扰而导致间隔棒倾斜缺陷识别易出现错检、漏检等问题,提出一种电网线路间隔棒倾斜缺陷识别方法。构建激光雷达成像模型来校正电网线路图像;采用黑、白高帽变换来区分图像潜在的黯淡、明亮区域,并输入到所设计的空间关注分类模型中,确定每个集群的最小超球体半径;根据状态判别方程,去除干扰,完成多目标干扰下的电网线路间隔棒倾斜缺陷识别。经实验验证:所提方法的平均精度均值保持在0.85以上,测试时间为600 s时的帧率(frame per second,FPS)为48.6 f/s;在间隔棒倾斜的状态下,所提方法缺陷识别的平均正确率为95.18%,平均召回率为86.37%,平均F1分数为0.90,表明所提方法不存在错检、漏检,且计算效率高、缺陷识别精度高,适用于各种环境下的电网线路间隔棒倾斜缺陷识别。
基金辽宁省博士科研启动基金(the Doctoral Scientific Research Foundation of Liaoning Province of China under Grant No.20061052)辽宁省教育厅高等学校科研项目资助(the Scientific Research Program of Higher Education of Liaoning Educational Committee of China under Grant No.20060484)
