Signal frequency

The ultrasonic images that we want to process are HF- type, (i.e., huilt from High Frequency signals. Fig. 4). Consequently, the noise is situated in the eentral part of the matrix. In order that we define two thresholds tl and t2. These last will be determined by using one of some measures quoted in the bibliography. 

Taking into account that it is necessary to make vary the flaw detector settings during the main part of the verifications, the total number of verifications is rather important. So, Technical Center for Mechanical Industries (CETIM) began the development of an electronic system enabling to benefit of the current possibilities of generation of synthesised radio frequency signals and help of personal computer for operator assistance and calculation. 

Figure Bl.5.15 SFG spectrum for the water/air interface at 40 °C using the ssp polarization combination (s-, s- and p-polarized sum-frequency signal, visible input and infrared input beams, respectively). The peaks correspond to OH stretching modes. (After [ ].)...

Nuclear magnetic resonance (nmr) requires an atomic nuclei that can absorb a radio-frequency signal impinging it in a strong magnetic field to give a spectmm. The field strength at which the nucleus absorbs is a function of both the nucleus and its immediate electronic environment. The atoms normally used for nmr analysis are as follows (34) H, F, P, Si, and Of these, the most commonly used in polymer analyses are... 

It is advisable in most of these cases to use accelerometers. Displacement probes will not give the high-frequency signals and velocity probes because their mechanical design is very directional and prone to deterioration. Figure 10-64 shows me signal from the various types of probes. 

After the pulse, we wait for a short whilst (typically a few microseconds), to let that powerful pulse ebb away, and then start to acquire the radio frequency signals emitted from the sample. This exhibits itself as a number of decaying cosine waves. We term this pattern the free induction decay or FID (Figure 1.3). 

In addition to their transporter function, perisynaptic transporters function as buffers to confine the extracellular free glutamate to receptors nearest the postsynaptic release sites. The total concentration of glial transporters in some CNS synaptic regions is estimated to be sufficient to bind the glutamate content of three to five vesicles per synapse [45]. This buffering , which occurs mostly in end-feet of astrocytes, is essential for reliable synaptic transmission of high-frequency signals [46]. 

Powerful and highly homogeneous electromagnet, radio-frequency signal generator and detector circuit, electronic integrator, glass sample tubes. 

A SAW device is configured as a delay line and fed by a radio frequency signal. Any change in the velocity Av is detected as a change AT in the phase delay of the wave, thanks to a phase detector that gives a voltage proportional to the difference of phase between signal input and output. 

The phase delay A(nwE) and modulation ratio M(na>E) information of the high-frequency signals is transferred to low-frequency signals by amplitude modulation (cross-correlation) of r.(t) and Iff) with a periodic train of pulses C(f) given by Ref. 29. 

On the other hand, the proposed approach has structure of low pass filter see Eq.(8). Thus, we can expect that the closed-loop response is not sensitive to high frequency signals (as, for example, by noisy measurements or fluctuations in fluids mechanics by agitation). Although Figure 3 depicts the frequency... 

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