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Ultrasonic testing of the second sampling

M factors; then use the parameters from the second sampling interval sampling of the implementation. Design process is shown in Figure 1 and Figure 2. Sampling interval algorithm flow chart in Figure 1 Experimental Comparison of the center frequency f 2, a 7.5MHz ultrasound radio frequency signal,[link widoczny dla zalogowanych], the A / D sample obtained after the source of the sample taken 2Os sequence (n), length of the N-10000; and then a second sample, Sample sequences are shown y (rn), length of the M-512. Figure 3a and c, as shown in Figure 2 taken the time domain to maintain a good flow and consistency of the source sequence waveform, but also in the process needs to retain some of the characteristics according to information here capture the peak . Respectively, z () and (G) for discrete Fourier transform (DTFT), have spectral density X () and Y (ea) (Fig. 3b and d), is still the center frequency 7.5MHz, but Y (ei ) center frequency bandwidth than the x (e) of the large, low frequency components increase in locally distorted. 3 Conclusion second sampling method is simple, the code overhead, the effect is similar to () low-pass filter; in the treatment of the defect can retain the characteristics of the sample peaks, including the magnitude of the sample and the sample sequence in the source the location,[link widoczny dla zalogowanych], it is a good quantitative assessment of defect size and position. But it applies to the source sample sequence length J \, larger than the display samples of the sequence length M (preferably N \References: E1] Li Jiawei, CHEN Ji Mao. NDT Manual [M]. Beijing: Mechanical Industry Press, 2002. [2] Feng Ruo. Ultrasound Manual [M]. Nanjing: Nanjing University Press,[link widoczny dla zalogowanych], 1997. Hong Yong et al: Ultrasonic testing of samples in the second helmet Jiao I '『I_0200040006000800010000 length (a) before processing the length of time-domain waveform 01O0200300400 (c) time domain waveforms after a second sampling 1O050512 Figure 3 results 0246810 Frequency / MHz (b) frequency domain before processing the waveform frequency / MHz (d) the frequency domain waveform after E3] VaidyanathanPP. MuhirateSystemsandFilterBanks [4] Hu Guang book. Digital Signal Processing - Theory, Algorithm and Implementation of EM]. North l-M]. EnglewoodCliffsNJ: Prentice-Hall, 1993. Beijing: Tsinghua University Press,[link widoczny dla zalogowanych], 1997. . . . . . . . . GB/T19348.1-2003 and GB/T19348.2-2003 standard has been officially released GB/Tl9348.1-2003 \2-2003 \page). . GB/Tl9348.1 used to determine the performance of film systems for industrial radiography film system and lead intensifying screens under the classification of combinations to ensure image quality of radiographs. The standard does not apply to the classification of fluorescence sensitized film. GB/Tl9348.2 Control of film processing system provides for the procedure. When working conditions are given,[link widoczny dla zalogowanych], they can control the film system performance. (Jin Yufei) 2004 World Engineers Conference Call for Papers 2004 World Engineers Conference will be held in November 2004 from 2 to 6 at the Shanghai International Convention Center. The General Assembly by the World Federation of Engineering Organizations and the UNESCO sponsored by the China Association for Science and Technology, Chinese Academy of Engineering, the Shanghai Municipal Government. Meeting received Science and Technology, Ministry of Education, Chinese Academy of Sciences, National Natural Science Foundation of China and the UNESCO Commission and the Hong Kong Institution of Engineers support. The General Assembly established the World Federation of Engineering Organizations, the first General Assembly, held in China is the highest level of engineering the largest international event industry. The theme is shaping the future of sustainable development engineers. The General Assembly established around the theme of the seven groups will be the issue. For questions breakout sessions, background and overview of the General Assembly, essay topics and submission requirements, please visit the Materials and Testing Network (www.mat-test.corn). (Chinese Mechanical Engineering Society) *】 79.5 O55OO one hundred and eleven> \ Xin 5) O55OO one hundred and eleven> \ Xin

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