For industrial computed tomography systems, generation II scan mode has a large field of view but time consuming and generation III has a small field of view but fast. In order to realize the rapid ICT test of large ...For industrial computed tomography systems, generation II scan mode has a large field of view but time consuming and generation III has a small field of view but fast. In order to realize the rapid ICT test of large objects, a scan mode based on generation III called large field of view scan was discussed and its reconstruction algorithm based on FBP was deduced. The validity of the algorithm was verified by the results of computer simulation and experiments. Analysis showed that the effective scan field of view could be improved by more than 90% compared with that of generation III.展开更多
The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period...The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window＇s central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.展开更多
A method of digitally high pass filtering in frequency domain is proposed to eliminate the background noise of the decoded image in Fresnel zone plate scanning holography. The high pass filter is designed as a circula...A method of digitally high pass filtering in frequency domain is proposed to eliminate the background noise of the decoded image in Fresnel zone plate scanning holography. The high pass filter is designed as a circular stop, which should be suitable to suppressing the background noise significantly and remain much low frequency information of the object. The principle of high pass filtering is that the Fourier transform of the decoded image is multiplied with the high pass filter. Thus the frequency spectrum of the decoded image without the background noise is achieved. By inverse Fourier transform of the spectrum of the decoded image after multiplying operation, the decoded image without the background noise is obtained. Both of the computer simulations and the experimental results show that the contrast and the signal-to-noise ratio of the decoded image are significantly improved with digital filtering.展开更多
In this paper, firstly, the bias between observed radiances from the Advanced TIROS-N Operational Vertical Sounder （ATOVS） and those simulated from a model first-guess are corrected. After bias correction, the obser...In this paper, firstly, the bias between observed radiances from the Advanced TIROS-N Operational Vertical Sounder （ATOVS） and those simulated from a model first-guess are corrected. After bias correction, the observed minus calculated （O-B） radiances of most channels were reduced closer to zero, with peak values in each channel shifted towards zero, and the distribution of O-B closer to a Gaussian distribution than without bias correction. Secondly, ATOVS radiance data with and without bias correction are assimilated directly with an Ensemble Kalman Filter （EnKF） data assimilation system, which are then adopted as the initial fields in the forecast model T106L19 to simulate Typhoon Prapiroon （2006） during the period 2-4 August 2006. The prediction results show that the assimilation of ATOVS radiance data with bias correction has a significant and positive impact upon the prediction of the typhoon＇s track and intensity, although the results are not perfect.展开更多
针对传统料堆体积测量方法存在数据采集不全面、数据形式不直观、存在误差累积等问题,提出一种基于激光雷达(light detection and ranging,LiDAR)三维扫描的料堆体积测量方法。利用部署在料堆顶部的激光雷达获取料堆真实的三维点云数据...针对传统料堆体积测量方法存在数据采集不全面、数据形式不直观、存在误差累积等问题,提出一种基于激光雷达(light detection and ranging,LiDAR)三维扫描的料堆体积测量方法。利用部署在料堆顶部的激光雷达获取料堆真实的三维点云数据,首先采用直通滤波算法裁剪并保留感兴趣区域(region of interest,ROI)点云数据,利用离群点滤波方法去除三维空间的噪点与不相关物体,再利用投影法重建地面,并通过上采样方法填补空缺,最后通过改进的alpha shape曲面重建算法得到料堆模型,以此计算其体积。实验结果表明,该方法可以准确测量固定区域的料堆体积,其平均测量精度达到98.32%,极大提高了散料体积的统计效率,降低人工成本。展开更多
文摘For industrial computed tomography systems, generation II scan mode has a large field of view but time consuming and generation III has a small field of view but fast. In order to realize the rapid ICT test of large objects, a scan mode based on generation III called large field of view scan was discussed and its reconstruction algorithm based on FBP was deduced. The validity of the algorithm was verified by the results of computer simulation and experiments. Analysis showed that the effective scan field of view could be improved by more than 90% compared with that of generation III.
基金This project is supported by National Natural Science Foundation of China(No.60377002).
文摘The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window＇s central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.
文摘A method of digitally high pass filtering in frequency domain is proposed to eliminate the background noise of the decoded image in Fresnel zone plate scanning holography. The high pass filter is designed as a circular stop, which should be suitable to suppressing the background noise significantly and remain much low frequency information of the object. The principle of high pass filtering is that the Fourier transform of the decoded image is multiplied with the high pass filter. Thus the frequency spectrum of the decoded image without the background noise is achieved. By inverse Fourier transform of the spectrum of the decoded image after multiplying operation, the decoded image without the background noise is obtained. Both of the computer simulations and the experimental results show that the contrast and the signal-to-noise ratio of the decoded image are significantly improved with digital filtering.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos KZCX2-YW-202 and KZCX2-YW-Q03-3)the Chinese Special Scientific Research Project for Public Interest (Grant No GYHY200906004)
文摘In this paper, firstly, the bias between observed radiances from the Advanced TIROS-N Operational Vertical Sounder （ATOVS） and those simulated from a model first-guess are corrected. After bias correction, the observed minus calculated （O-B） radiances of most channels were reduced closer to zero, with peak values in each channel shifted towards zero, and the distribution of O-B closer to a Gaussian distribution than without bias correction. Secondly, ATOVS radiance data with and without bias correction are assimilated directly with an Ensemble Kalman Filter （EnKF） data assimilation system, which are then adopted as the initial fields in the forecast model T106L19 to simulate Typhoon Prapiroon （2006） during the period 2-4 August 2006. The prediction results show that the assimilation of ATOVS radiance data with bias correction has a significant and positive impact upon the prediction of the typhoon＇s track and intensity, although the results are not perfect.
文摘针对传统料堆体积测量方法存在数据采集不全面、数据形式不直观、存在误差累积等问题,提出一种基于激光雷达(light detection and ranging,LiDAR)三维扫描的料堆体积测量方法。利用部署在料堆顶部的激光雷达获取料堆真实的三维点云数据,首先采用直通滤波算法裁剪并保留感兴趣区域(region of interest,ROI)点云数据,利用离群点滤波方法去除三维空间的噪点与不相关物体,再利用投影法重建地面,并通过上采样方法填补空缺,最后通过改进的alpha shape曲面重建算法得到料堆模型,以此计算其体积。实验结果表明,该方法可以准确测量固定区域的料堆体积,其平均测量精度达到98.32%,极大提高了散料体积的统计效率,降低人工成本。
