Noise signal dependent

Figure 4. Improvement in sensitivity with the CAT. PFA and a reference peak at m/e 315. The observed improvement in signal-to-noise ratio results from the longer total scanning time and also the fact that many sweeps are made during this time. The overall improvement in signal-to-noise ratio depends on the detailed power spectrum of the noise (9). Resolution 12,000 here and for all following time averaged spectra...

The absolute strength of the MRI signal depends on many factors including the number of nuclear spins in an imaging voxel. Thus, there is a tradeoff between image resolution and signal-to-noise ratio, S/N. For the commonly used granular... 

At either frequency the sensitivity of the instrument is quite remarkable. The exact signal-to-noise ratio depends upon a number of factors including apparent line width (including g and hyperfine anisotropy), ease of saturation, the temperature, and the linear density of the sample in the quartz tube. For a relatively narrow line with peak-to-peak separation of two gauss it is possible to observe the spectrum for concentrations as low as 1014 spins per gram of sample. As the spectrum becomes more anisotropic, the sensitivity of course decreases. Lowering the temperature increases the sensitivity since the population difference An increases [(Eqs. (26) and (3°)]. 

This principle can be extended to different models including signal dependent noise (clutter) [19]. In this case, one must take the non-linear term into account in the signal to interference plus noise equation ... 

Figure 10. Target-matched illumination with signal-dependent noise (clutter).

Pillai, S.U., Oh, H.S., Youla, D.C. and Guerci, J.R., Optimum transmit-receiver design in the presence of signal-dependent interference and channel noise , IEEE Trans. Information Theory, Vol.46, No.2, pp 577-584, March 2000. 

Stochastic resonance is a kinetic effect universally inherent to bi- or multistable dynamic systems exposed to either white or color noise. Its main manifestation is the appearance of a maximum on the noise intensity dependencies of the signal-to-noise ratio in a system subject to a weak driving force. Essentially, this behavior is due to the presence of an exponential Kramers time x cx exp(AU/3>) of the system switching between energy minima here AU is the effective height of the energy barrier separating the potential wells and 3> is the noise intensity. 

Signal and signal-to-noise ratio depend upon the passage of the light beam from the lamp through the flame centre at the optimum height. Thus the burner position must be optimized in three respects ... 

Shot noise — originates from the movement of charge carriers when they cross n-p junctions or arrive at an electrode interface. It is much smaller than thermal noise and depends on the signal as follows C/shot = R(2IeA/) /2. [/shot is the -> root mean square amplitude... 

Heteroscedastic noise. This type of noise is dependent on signal intensity, often proportional to intensity. The noise may still be represented by a normal distribution, but the standard deviation of that distribution is proportional to intensity. A form of heteroscedastic noise often appears to arise if the data are transformed prior to processing, a common method being a logarithmic transform used in many types of spectroscopy such as UV/vis or IR spectroscopy, from transmittance to absorbance. The true noise distribution is imposed upon the raw data, but the transformed information distorts this. 

Although several other important nuclides can be detected by NMR, proton ( H) remains the most widely used because of its high sensitivity, high isotopic natural abundance (99.985%), and ubiquitous presence in organic compounds. Of comparable importance is carbon ( C), 1.108% abundance, which, because of substantial improvements in instrument sensitivity, is now utilized as routinely as proton. Fluorine ( F), 100% abundance, is less used since it is present in only about 10% of pharmaceutical compounds. Another consequence of the intrinsic low sensitivity of NMR is that virtually all samples require signal averaging to reach an acceptable signal-to-noise level. Depend-... 

The detectors fitted to infrared spectrometers provide an electrical signal dependant on the incident luminous flux. Their sensitivity is estimated by the Noise Hquivaient Power (NEP). This is the radiation power required to obtain an electrical signal equal to the noise generated by the detector. The inverse of this quantity per unit of useful surface and per unit bandwidth is the specific detective capacity D, The choice of a detector involves consideration of its sensitivity in the spectral domain under study and the required response time as well as its purchase and operating costs (some are cooled to liquid nitrogen temperature). 

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