Systematic noise

In this relation a(r, t) is the experimentally observed signal, s represents random noise, axi r) represents the time invariant systematic noise and aRi(f) the radial invariant systematic noise Schuck [42] and Dam and Schuck [43] describe how this systematic noise is ehminated. x is the normahsed concentration at r and t for a given sedimenting species of sedimentation coefficient 5 and translational diffusion coefficient D it is normalised to the initial loading concentration so it is dimensionless. 

Thus, in looking at telepathy, we encounter the problem of systematic noise, as well as random noise, on the channel. Although it is most obvious in telepathy experiments, in which... 

One d i sad vantage ot the iiseof randont nttisc excitation in. spectro.scopy and imaging isthe unavoidable presence of systematic noise as a consequence of the variance of the power spectral density of the excitation It is reduced but not eliminated by formation of... 

In pulse NMR, there is always noise coherent with the pulse sequence because of the transient nature of the experiment. This is in addition to the usual random noise as well as other systematic noises such as the 50 or 60 Hz "hum from the ac source which are not synchronized with the pulses. These non-synchronous components of noise can be reduced either by appropriate filtering or by multiscan averaging or both. In this section we will deal with noise coherent with the pulse sequence. Even if such noises were very small, they will add upon signal averaging (just like the desired signal) and may, therefore, be troublesome in experiments where very many FID s are accumulated due to inherently poor S/N. 

Finally, neither the effect of external noise, which affects nonequilibrium transitions in chemical and biological systems (Lefever, 1981 Horsthemke Lefever, 1984 Lefever Turner, 1986), nor the stochastic aspects of these transitions (Nicolis, Baras Malek-Mansour, 1984) are considered - with the exception of the glycolytic system (chapter 2). Such a simplification, justified in the first approximation by the absence of systematic noise in the biological systems considered, permits us to avoid complicating from the outset the analysis of systems whose kinetics is already complex. 

The spin temperature alternation was used to reduce systematic noise sources as discussed by Stejskal and Schaefer for solids... 

Measurement of samples at low concentration may be expected to yield signals badly contaminated by random and systematic noise. Techniques for noise reduction may be applied both in the design and the operation of the spectrometer and in post-detection data processing (Section 4.2). The utility and flexibility of these techniques have been greatly enhanced by the computing power now available from desk-top computers that can be attached on-line to a spectrometer in order simultaneously to process its output and optimise its working parameters. Some of the techniques that have been used are described in Section 4.3 and their development for measurements up to atmospheric pressure is discussed in Section 4.4. 

In order to find the minimum number of components, p, necessary for data reproduction within residual error, the components are added step by step to the model according to equation (8). After each step the data matrix is reproduced and the procedure continues until only non-systematic noise ... 

Therefore the shape of the distribution will be variable on the arcmin scale. The degradation of source location accuracy caused by loss of the shadow-gram contours could be reduced by choosing a collimator pitch larger than the mask element. In this case, however, off-axis sources may induce artifacts in the image, the spatial distribution of which depends on the particular mask design chosen. The normalized rms, associated to this systematic noise, increases with both the ratio between the sizes of the collimator ceU and the mask element, and the source offset angle. 

PLS may be inferior to those from PCR when spectral intensity varies nonlinearly against concentration due to a systematic error [2], The PLS method is expected to be superior for handling spectra with random noise, whereas the PCR method should be applied to spectra with systematic noise. Thus, it is desirable to decide, prior to performing a spectroscopic calibration, which of the two methods should be employed. 

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