Fluctuation noise

Unsteady noise can be evaluated by a phonometer, which measures the sound pressure level for a time period of noise fluctuation and gives the time-weighted average value. 

Electrochemical noise. Fluctuations in potential or current from baseline values during electrochemical measurements are particularly prominent during active/passive transitions. This so-called electrochemical noise is of particular value in monitoring localised corrosion, i.e. pitting, crevice and deposit corrosion and stress-corrosion cracking . 

Determination of electrochemical noise fluctuations of the free potential or fluctuations of the current when a constant potential is maintained. 

Wiesenfeld, et. al. [wiesen89] compare the simplicity of the independent relaxation time interpretation of l//-noise fluctuations in the saudpile CA model to other recent models yielding 1// noise ... 

We only had to add one more term - spontaneous emission - to the equation. Well, we did that, and then I had a hard time solving the equation, but a mathematician, Dr. [G.] Takahashi solved it. So Takahashi, Shimoda and I then wrote a paper on the maser amplifier, what the noise had to be, the theory of the noise fluctuations, and so on. Again, just trading ideas back and forth. 

A problem encountered with atomic absorption is that emission from the flame may fall on the detector and be registered as negative absorption. This can be eliminated by modulating the light source, either mechanically or electronically, and using an a.c. detector tuned to the frequency of modulation of the source. D. C. radiation, such as emission from the flame, will then not be detected. A high intensity of emission, however, may overload the detector, causing noise fluctuations. 

Theoretical considerations shown in the above equation also indicate that peak area precision is inversely proportional to the peak sig-nal/noise ratio, and to the number of sampling points across the peak width. For very noisy peaks, the peak area precision is limited by random noise fluctuations (Figure 6). Figure 7 shows that the precision of the peak area degrades rapidly when the signal-to-noise ratio is less than 100. Statistical considerations also stipulate a minimum data sampling... 

The input multiplexer was designed to allow multi-channel capability and was configured to monitor both potential and current noise fluctuations sequentially on a maximum of eight pairs of samples. 

Just as others who have used linear methods, this author was disappointed to note the appearance of spurious nonphysical components when he applied the linear relaxation methods (Chapter 3) to the deconvolution of infrared spectra. Infrared absorption spectra, and other types of spectra as well, must lie in the transmittance range of zero to one. Spurious peaks appeared to nucleate on specific noise fluctuations in the data and grow with successive iterations, even though the mean-square error... 

To sum up, the Kurizki-Shapiro-Brumer photocurrent coherent control exhibits resilience to noise and fluctuations. Nevertheless, excessive noise will degrade or completely destroy the effect. We therefore turn to noise/fluctuation control in what follows. 

Figure 4.19 Transfer infidelity 1 - F T) for a modulated boundary-controlled coupling a tt) = a sin C y) as a function of (a) the transfer time T. (inset) the maximum value of the boundary coupling and (b) the perturbation strength Cj of the noisy channel, averaged over 10 noise realizations for = 0.6 and = 0.7. In static noisy channels, the infidelity obtained under static control p = 0 (empty circles) is shown to be strongly reduced under dynamical p = 2 control (empty squares). A fluctuating noisy channel is less damaging in the Markovian Unfit where the correlation time of the noise fluctuations 0 (p = 0, green solid circles), the infidelity converges to its unperturbed value.

Professor Eisenman, there is a large body of results indicating the existence of channel systems. One could mention the Ca2+ ATPase of sarcoplasmic reticulum, the FF transporting ATPase of the inner mitochondrial membrane, the purple protein system of halobacteria, the Na and K+ channels of the axonal membranes. Apart from the classical type of evidence provided, for example, by the noise fluctuation technique, we now even begin to see direct electron microscopic evidence for the existence of transport-related openings in biological membranes. On the other hand, solid evidence for the existence of mobile carriers in eucaryotic cell membranes is very scarce, if not outright absent. 

Experiments indicate that ions are almost two orders of magnitude more efficient than 20 keV electrons 54). This is because the energy of the ions is more completely absorbed in the resist layer. The high sensitivity can be a problem, however, for very high resolution because of inherent noise fluctuations created by the small number of ions needed to expose an image element (55). At an exposure dose of 10 8 C/cm2, only 6 ions will expose a 0.1 /urn x 0.1 /urn element resulting in an exposure uncertainty of 40%. This is not satisfactory. 

However, this charge pulse contains switching noise caused by the MOS-FETs. Since the linear image sensor have many Si ICs, this switching noise fluctuates because of nonuniformity in MOSFET characteristics. Therefore an efficient noise reduction technique is required for this sensor (Ozawa et al., 1982 Kaneko et al., 1982), as in the case of Si monolithic MOS image sensors (Ashikawa et al., 1973 Aoki et al., 1980). 

A noise that has a clearly distinct origin from noise discussed in previous sections is the electric noise that originates in modulation of ion transport by fluctuations in system conductance. These temporal fluctuations can be measured, at least in principle, even in systems at equilibrium. Such a measurement was conducted by Voss and Clark in continuous metal films (44). The idea of the Voss and Clark experiment was to measure low-frequency fluctuations of the mean-square Johnson noise of the object. In accordance with the Nyquist formula, fluctuations in the system conductance result in fluctuations in the spectral density of its equilibrium noise. Measurement of these fluctuations (that is, measurement of the noise of noise) yields information on conductance fluctuations of the system without the application of any external perturbations. The samples used in these experiments require rather large amplitude conductance fluctuations to be distinguished from Johnson noise fluctuations because of the intrinsic limitation of statistics. Voss and... 

Random noise fluctuations (including digitization round-off). 

Under typical controlled conditions, the baseline offset values change relatively slowly over time, and the signal and noise fluctuate more rapidly over time. 

In detectors employing an electrical readout mechanism, electrical noise fluctuations (Johnson noise plus possibly other noise sources such as low frequency contact noise in some cases) must be considered. There will be a Johnson noise source associated with the output impedance of the detector. In thermopiles and bolometers the output impedance is predominantly resistive so that the calculation of the Johnson noise is straightforward. The output impedance o f the pyroelectric detector is predominantly capacitative. In this case the resistive component associated with the dielectric loss factor of the... 

Models of population growth in random environment have been constructed by inserting white noise fluctuations in the deterministic growth equations (May, 1972 Capocielli Ricciardi, 1974 Ricciardi, 1977 Nobile Ricciardi, 1984a, b). The structure of these models is similar to those described in Section 5.8 ( external fluctuations ) and we shall not discuss them here. 

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