Signal filtering

Fig. 5 (a) Ultrasonic signal overlapped by a thermal component (observation time of 100 iis), (b) Low frequency ultrasonic signal filtered (observation time of 10 ns). 

A more complex but faster and more sensitive approach is polarization modulation (PM) IRLD. For such experiments, a photoelastic modulator is used to modulate the polarization state of the incident radiation at about 100 kHz. The detected signal is the sum of the low-frequency intensity modulation with a high-frequency modulation that depends on the orientation of the sample. After appropriate signal filtering, demodulation, and calibration [41], a dichroic difference spectrum can be directly obtained in a single scan. This improves the time resolution to 400 ms, prevents artifacts due to relaxation between measurements, and improves sensitivity for weakly oriented samples. However, structural information can be lost since individual polarized spectra are not recorded. Pezolet and coworkers have used this approach to study the deformation and relaxation in various homopolymers, copolymers, and polymer blends [15,42,43]. For instance, Figure 7 shows the relaxation curves determined in situ for miscible blends of PS and PVME [42]. The (P2) values were determined... 

Giernoth, R. and Bankmann, D., Application of diffusion-ordered spectroscopy (DOSY) as a solvent signal filter for NMR in neat ionic liquids., Eur.. Org. Chem., 4529,2005. 

Transducers that use torsion bars or springs of known compliance may also oscillate at the beginning of the test as the step is imposed. This ringing is symptomatic of the detector and not the sample response, and thus needs to be removed by signal filtering. In a creep test this kind of behavior only occurs if the sample is... 

Steady-state extrapolation Fourier analysis Gating and signal filtering Transient signals Speeding up of response Spatial and temporal information Enhancement of selectivity Increasing order of measurement... 

Note that, mathematically, representation (4.179) is not complete. Indeed, in a general case the exact amplitude of the mu mode must contain, along with the contribution c", an infinite set of terms E,"+2, E,"44, and so on. However, in a weak-field limit c < 1 the terms with higher powers are of minor importance so that the main contribution to the magnetization response signal filtered at the frequency no is proportional to c". 

Band gap -> semiconductor Band-pass filter -> signal filtering Band-stop filter -> signal filtering Bardeen-Cooper-Schrieffer theory -> BCS theory Barker, Geoffrey Cecil... 

Signal filtering — A process used to eliminate unwanted frequencies, generated by electronic devices during the detection procedure, from a measured signal. Different analog filters and digital filters have been developed... 

Signal filtering — Figure. Filter types a low-pass, b high-pass, and c band-pass... 

If the reagents react rapidly, then in-line control of pH is practical, with a signal filter to reduce the noise. A pump or inline static mixer should be used to provide thorough mixing of the process and reagent as shown in Figure 3.27 (A) and (B). 

The elements of the robust monitoring strategy builds on the methods discussed previously (e.g., PC A in 3.1 and signal filtering in 6.2.3). Here, only the key variations will be introduced. 

Sheet forming processes have univariate MD and multivariate CD controllers. Process dynamics for both are dominated by gain and time delay. Most of the appreciable dynamics arise from the design of signal filters and... 

Filters are used to select a special emission wavelength, to suppress excitation light in fluorescence experiments, and to adjust the intensity of a light signal. Filters can be based on absorption in coloured glass or on reflection and interference in a stack of dielectric and metal layers. 

Signal Filtering For FT filtering, the signals are transformed from the time domain according to Eq. (3.18) into the frequency domain, F v). After that, multiplication by a filter function, H v), and back transformation with the inverse FT function (Eq. (3.20)) are performed. The filtered data, G(v), are obtained by... 

Note the similarity to signal filtering in Eq. (3.24). One difference compared to deconvolution is the type of the... 

In Figure 3.12, a filtering effect can also be seen in connection with the reduction of coefficients. The difference from the aforementioned methods of signal filtering lies only in the concrete choice of the filter coefficients. The principle of back transformation is the same here as in the case of data reduction. 

In Section 3.2.3 it was shown that a resonance falling outside the spectral window (because it violates the Nyquist condition) will still be detected but will appear at an incorrect frequency and is said to be aliased or folded back into the spectrum (if digital signal filters are not employed to eliminate this). This can be confusing if one is unable to tell whether the resonance exhibits the correct chemical shift or not. The precise location of the aliased signal in the spectrum depends on the quadrature detection scheme in use and on how far outside the window it truly resonates. With the simultaneous (complex FT) scheme, signals appear to be wrapped around the spectral window and appear at the opposite end of the spectrum (Fig. 3.24b), whereas with the sequential (real FT) scheme, signals are folded back at the same end of the spectrum (Fig. 3.24c). If you are interested to know why this difference occurs, see reference [7]. 

---