Noise INDEX

The purely molecular communication channel [9,38,46-48], with p defining its input signal, is devoid of any reference (history) of the chemical bond formation and generates the average noise index of the molecular IT bond covalency, measured by the conditional entropy S(b system outputs given inputs ... 

Jevtic, M.M. et al. 1999. Thick-film resistor quality indicator based on noise index measurements. Microelectronics Journal, 30, pp. 1255-1259. 

Resistor noise is an effective method of measuring the quality of the resistor and its termination. On a practical level, noise is measured according to MIL-STD-202 on a Quantech Noise Meter. The resistor current noise is compared to the noise of a standard low noise resistor and reported as a noise index in decibel. 

The noise index is expressed as microvolt/volt/frequency decade. The noise measured by MIL-STD-202 is 1 /f noise, and the measurement assumes this is the only noise present. However, there is thermal or white noise present in aU materials that is not frequency dependent and adds to the 1/f noise. Measurements are taken at low frequencies to minimize the effects of thermal noise. The noise index of low-value resistors is lower than high-value resistors because the low-value resistors have more metal and more free electrons. Noise also decreases with increasing resistor area (actually resistor volume). 

Noise index A measurement of the amount of noise generated in a component as a result of random movement of carriers from one energy state to another. 

The noise index NI in dB is measured by a band-pass filter (bandwidth of 1 kHz between 618 Hz and 1618 kHz) [51]. A noise index NI = 0 dB corresponds to 1 pV noise voltage per 1 V DC voltage. For ruthenate-based TFRs, the noise index exhibits an increase proportional to the sheet resistivity and a decrease proportional to the resistor area [47,52]. 

The Index n = k- ) - M + m is the current variable that indicates the sequence for the beam projections. Exploiting the current measurings y fn) one has to estimate the unknown image parameters a, with undefined conditions about their distribution and the noise FDD function. 

It is evident that most studies reported to date have used number density, average size or weight per eent as eontrol variables. Often these variables are inferred from other measurements, ineluding density, solution supersaturation, refraetive index ete. Inferential teehniques have been shown to be partieularly suitable for industrial seale applieations where laser seattering deviees for on-line size distribution measurement are not yet praetieal for industrial eontrol purposes, although substantial progress is being made to that end. Even when usable, however, these measurement deviees are often eharaeterized by noise and require operation at very low solids eoneentration. 

Eor amine-containing polymers, DMF is often a good choice of solvent. DMF can also be a good choice for polymers of higher carboxylic acid content. However, DMF does present some experimental difficulties. It must be run at an elevated temperature, typically 60°C, because of its viscosity. Also, because most polymers have a much lower refractive index response in DMF, the signal-to-noise ratio for a polymer in this solvent is diminished versus the same ratio for common acrylates in THF. 

The flow sensitivity of a detector will also be one of the factors that determines the long term noise and thus will influence the sensitivity or minimum detectable concentration of the detector.lt is usually measured as the change in detector output for unit change in flow rate through the sensor cell. Again, the refractive index detector is the most sensitive to flow rate changes. 

Refractive index detectors are not as sensitive as uv absorbance detectors. The best noise levels obtainable are about 1CT7 riu (refractive index units), which corresponds to a noise equivalent concentration of about 10-6 g cmT3 for most solutes. The linear range of most ri detectors is about 104. If you want to operate them at their highest sensitivity you have to have very good control of the temperature of the instrument and of the composition of the mobile phase. Because of their sensitivity to mobile phase composition it is very difficult to do gradient elution work, and they are generally held to be unsuitable for this purpose. 

The basic situation is illustrated in Figure 27-1. What we have here is a simulation of an ideal case a transmission measurement using a perfectly noise-free spectrometer through a clear, non-absorbing solvent, with a single, completely soluble analyte dissolved in it. The X-axis represents the wavelength index, the T-axis represents the measured absorbance. In our simulation there are six evenly spaced concentrations of analyte, with simulated concentrations ranging from 1 to 6 units, and a maximum simulated... 

Using the modelling approach above, the predicted response of a CO2 correlation spectroscopy system will now be shown. This requires knowledge of the transmission spectrum of CO2 gas, so that predictions from the model can be made, for the expected modulation index, SNR (signal to noise ratio) and cross-sensitivity to a contaminant gas. 

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