Signaling process

Figure 3 Echo from 8 mm side-drilled hole at sound path 50 mm, before and after signal processing.

Chan,R.W.Y., Hay,D.R., Matthews,J.R., MacDonald,H.A., (1988), Automated Ultrasonic System for Submarine Pressure Hull Inspection , Signal Processing and Pattern Recognition in Nondestructive Evaluation of Materials, C.H.Chen (ed). Springer-Verlag, pp. 175-187... 

G. Demoment, IEEE Trans, on Acoust., Speech, Signal Processing 37 12, pp. 2024-2036 (1989)... 

Braun, H., Hauck, A. Tomographic reconstruction of vector fields. IEEE Trans, on Signal Processing, 1991, 39(2) fOf-fll. 

H.S. Malvar, "Signal processing with lapped transforms", Ed. Artech House, Inc., 1992. 

Signal Processing Algorithms in Mechanised Ultrasonic Testing. 

PARADISE (L.), Development of methods and a device of signal processing adapted to NDT by ultrasonic waves. Thesis of Doctor Engineer, INP Grenoble, 1983. 

DE VADDER (D.) and DOSSO (M.), Ultrasonic characterization of crack edges by numerical signal processing, Third European Conference of NDT, Florence, 1984. 

Limited capabilities as the instrument carries out an analog measurement, on-line signal processing of data is almost impossible. All analysis tasks must be done off-line, and cost is increased (equipment, specialists). 

VME bus. It is possible to plug other standard VME boards in the ET instrument. For example, it is possible to add a DSP board, and carry out on-line analysis. But there is also CPU time left to add signal processing on the eddy current board itself. (For example on-line mixing of signals at 2 different frequencies). 

The DSP has enough time to do some on-line signal processing combinations between channels, or noise reduction. 

A. Mohammad-Djafari M. Nikolova. Eddy current tomography using binary markov model. Signal Processing, 49 119-132, 1996. 

O. Venard. Eddy current tomography a bayesian approach with a compound weak membrane-beta prior model. In Advances in Signal Processing for Non Destructive Evaluation of Materials, 1997. 

O. Rioul and M. Vetterli "Wavelets and signal processing" IEEE SP magazine, October 1995... 

Constant steps are not necessary, but they simplify the matrix g of eq.(6). Eq.(5) and eq.(6) respectively show the relationship between input and output signal for discrete signal processing. It is given by a linear equation system, which can easily be solved. 

Nijnieijer, M.C, Boer, M.A. Correction of lens-distortion for real-time image processing systems. VLSI Signal Processing VI... 

G.S. Kino, Acoustic waves devices, imaging and analog signal processing (Prentice-Hall, Englewood Cliffs, New Jersey, 1987). 

Shear Horizontal (SH) waves generated by Electromagnetic Acoustic Transducer (EMAT) have been used for sizing fatigue cracks and machined notches in steels by Time-of-Flight Diffraction (TOED) method. The used EMATs have been Phased Array-Probes and have been operated by State-of-the-art PC based phased array systems. Test and system parameters have been optimised to maximise defect detection and signal processing methods have been applied to improve accuracy in the transit time measurements. 

The image without treatment (Fig lb) should be compared with the deconvolved image of the rod (Fig. 2b). The dimension of the rod is well restored and the contour is reinforced by the signal processing. 

To restore resolution, we proposed a signal processing method based on Papoulis deconvolution. We implemented this algorithm and tried to operate an improvement from an aluminum rod smaller than the wavelength. 

Signal processing in mechanical impedance analysis (MIA) pulse flaw detectors by means of cross correlation function (CCF) is described. Calculations are carried out for two types of signals, used in operation with single contact and twin contact probes. It is shown that thi.s processing can increase the sensitivity and signal to noise ratio. 

The modern Russian MIA flaw detectors use pulse version of the method [1-3], which peirnits to produce very portable (0.7 - 1.5 kg) and simple instruments, convenient especially for in-service testing. The objects to be tested are multilayer structures of reinforced plastics, metals and other materials honeycomb panels, antenna fairings, propellers, helicopter rotors and so on. In mentioned instruments amplitude-frequency analog signal processing is used. 

So the correlative processing gives additional (to the amplitude) variation of output signal and makes the signal processing a multiparamctric one. Such processing increases the sensitivity and reduces the noises. 

Correlative signal processing in MIA pulse flaw detectors is an effective way to increase the sensitivity and signal to noise ratio. Instruments with such processing system should be provided with a device for adjusting and sustaining initial phases of both current and reference pulses. 

The evaluation of the deconvolution results show that time resolution is better or equal to 1 with the chosen processing time unit of 0.08 microseconds (respectively a rate of 12.5 MHz). First signals processed conservatively have been acquired with a samplerate of 12.5 MHz. A Fourier analysis shows that the signals spectras do not have energy above 2.0 MHz. This means that a sampling rate of 4.0 MHz would have done the job as well. Due to the time base of the ADC an experimental check with a sample rate of 5.25 MHz has been carried out successfully. 

Materials to be inspected are, for example Concrete with lest frequencies of about 50 kHz, sandwich components with 500 kHz, metallic materials up to 10 MHz and thin components up to 35 MHz. Apart from the difference of materials, variable thicknesses and attenuations require different amplifications and signal processings. 

A signal processing scheme to enhance the signal to noise ratio,... 

Nonlinear optical properties are of interest due to their potential usefulness for unique optical devices. Some of these applications are frequency-doubling devices, optical signal processing, and optical computers. 

Signal processing. The mechanisms involved in analyzing, routing, sampling, or changing the representation of a signal. 

Sigma (s-) receptors Signal flares Signaling smokes Signal modulators Signal processing... 

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