Sampling frequency maximum

For each of the columns in table 7.2 the hold-up time (t0) can readily be calculated from eqn.(7.6) using k=0. The standard deviation in time units follows from t0 after division by vN (eqn.1.16). Eqns.(7.35) and (7.36) then provide the maximum allowable detection time constant (r), the required sample frequency for digital data handling (/) and the required number of datapoints (Ndat) for recording a chromatogram (0 < k< 4). All these characteristics are shown for the different columns in the bottom part of table 7.2. 

In this section we have derived rules of thumb for the maximum allowable extra-column dispersion and detection time constant and for the minimum required sample frequency for digital data handling. 

Because of the varying density of sampling frequencies, the spectrum of contributions to the charge-fluctuation force has a maximum. Over the frequency range at which A(/ )2 is constant, the contribution to the force increases as a function of frequency because of the increasing density of sampling frequencies. Over the frequency range at which A(/ )2 decreases to zero, the contribution to the force ceases (see Fig. LI.11). 

Sampling Frequency A perfect reconstruction of a signal is possible when the sampling frequency is greater than twice ( 2.3x) the maximum frequency of the signal being sampled. 

The rabber modulus increases with an increasing volume fraction of Aerosil. The modulus increase can be caused by the elastomer-filler and filler-filler interactions and by an increase of effective filler content. A very sharp peak for the tanZ is observed at 163 K for an unfilled crosslinked sample. This maximum corresponds to the glass transition of the rubber. Furthermore, it is observed that the Tg of the rubber does not change in the presence of filler. However, the second maximum of to 5 can be seen in the vicinity of 200 K for filled samples. The intensity of this maximum becomes more pronounced with increasing Aerosil content. This observation is in agreement with the results of the h and Ty relaxation study, as demonstrated in Fig. 4a and 6, respectively. Therefore, it seems reasonable to assign the maximum for at 200 K to the motion of adsorbed chain units. This maximum is observed at a lower temperature than the H and T, minimum for the adsorbed chain units (at about 280 K) due to difference in frequency of these methods 1.6 Hz and 46-90 MHz, respectively. 

Fast and low power consumption PMT read-out electronics is designed using of VLSI-ASIC boards. The LIRA chip, developed by NEMO, is capable to sample PMT signals at 200 MHz sampling frequency with 10 bits dynamic range, moreover trigger thresholds can be remotely controlled on shore. The LIRA maximum dissipation is <200 mW. 

PAHs have been detected in urban runoff generally at concentrations much higher than those reported for surface water. Data collected as part of the Nationwide Urban Runoff Program indicate concentrations of individual PAHs in the range of 300-10,000 ng/L, with the concentrations of most PAHs above 1,000 ng/L (Cole et al. 1984). In a recent study by Pitt et al. (1993) which involved the collection and analysis of approximately 140 urban runoff samples from a number of different source areas in Birmingham, Alabama, and under various rain conditions, fluoranthene was one of two organic compounds detected most frequently (23% of samples). The highest frequencies of detection occurred in roof runoff, urban creeks, and combined sewer overflow samples. The maximum reported concentration of fluoranthene in these samples was 130 jag/L. 

The complex viscosity as a function of frequency, maximum strain and temperature is generally determined with one rheometer. Standard ASTM 4440-84/90 defines the measurement of rheological parameters of polymer samples using dynamic oscillation. This standard reiterates the importance of determining the linear viscoelastic region prior to performing dynamic frequency sweeps. 

The sampler should be fast, as its maximum sampling frequency is often the limiting factor for the sampling rate. The availability of this component also permits carryover compensation according to Eq. 5.12, as the frequency of sample insertions, and consequently the carryover coefficient, is maintained. The sampling rate is then improved, as discussed in 5.6.6.2. 

Determination of maximum sampling frequency. Expand the recording time axis 10-fold. Inject a sample and record the rise and fall of the peak. Measure the distance from baseline to baseline on the peak and convert this to seconds. This will represent the minimum time between injections. Report the maximum sampling frequency in samples per hour. 

Figure 2.12. Factors influencing the maximum sampling frequency. The hatched area shows the peak overlap, which for it = 4 in this figure is 4% of the respective areas.

Rule 6. To obtain maximum sampling frequency the flow system should be designed to have minimum Sm and should be operated by injecting the smallest practical sample volume Sjj. FIA systems with minimum dispersion factor P1/2 will require the least volume of reagent solution and will yield maximum sampling frequency in relation to residence time of the zone continuously moving through the channel. 

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