Peak threshold value

The powder X-ray diffractograms of the composites present the characteristic peaks of the encapsulated zeolite [9]. It is interesting to observe that no characteristic peak of chitosan was present in the XRD patterns of composites. It is clear that the presence of the zeolites has prevented the crystallisation of chitosan when the gel has been dried. This phenomenon has been already observed when the zeolite content reaches a threshold value and has been attributed to a strong interaction between zeolite and chitosan [10],... 

When the averaged slope of the signal between bnnch B1 and B3 is greater than or equal to the liftoff threshold value, the software flags B1 as the possible peak start. The algorithm then examines the individual raw data points that make up B1 to determine the actual start of the... 

Peak threshold. All peaks in the acquired spectrum below the intensity threshold value (measured usually as a percentage of the most intense peak in the spectrum) will not be used in the calibration procedure. 

Like CRF-1, CRF-2 also favors short analysis times and well resolved peaks. However, there is no threshold value for resolution, and the compromise between resolution and analysis time is not as well defined as in CRF-1. Inclusion of analysis time in the denominator of an objective function may result in the loss of some resolution, compensated for by a rapid analysis time (51). This is likely to occur to some extent when the resolution threshold is defined in excess of 1 to 1.25, since the peak-valley ratio utilized by CRF-2 does not diminish to an appreciable extent until the resolution falls below this range. Note that as the resolution drops below 1 to 1.25, however, CRF-2 decreases rapidly, and it is unlikely that a short analysis time will compensate for such poor resolution (33). Nevertheless, if a user-specified minimum resolution is an absolute requirement, it is probably better to use a threshold criterion such as CRF-1 in which the desired resolution is stipulated by the user. 

We are pleased that the approach and the methodology developed for supports such as -y-Al203 are also applicable to zeolites (35). For example, when a mixture of NaCl (mp 801°C) and a zeolite, namely, NaY, is subjected to a heat treatment at 550°C for 24 h, the XRD peaks of NaCl will disappear or recede depending on whether the loading of NaCl is lower or higher than the threshold value, as is shown in Fig. 14. 

Eqn.(4.10) also provides insight into the threshold value for P for symmetrical peaks. According to eqn.(4.10) P will be estimated as zero for... 

This figure applies to Gaussian peaks, but clearly, for peaks of other shapes there will also be some threshold value below which changes in the extent of separation will not be reflected in P. 

Below a certain threshold resolution, no valley can be observed between two adjacent peaks in a chromatogram. In that case the value for any of the peak-valley ratios would equal zero. In theory, the value for Rs and S would exceed zero for any two peaks that have different retention times (At > 0). In practice, this difference vanishes if the presence of two peaks cannot be discerned from the chromatogram. However, the occurrence of ill-resolved peaks in a chromatogram may be recognized visually at resolutions well below 0.6 (the threshold value below which P equals zero for Gaussian peaks of equal height) (see ref. [401], figure 2.11, p.38). Moreover, there are several techniques which may be of... 

Above a certain threshold value for the number of plates, a pair of peaks will become irrelevant for the determination ofZP. When this threshold is reached for all pairs of peaks, ZP will have reached its limiting value. Changes in N will no longer be reflected in ZP, whereas changes in the (relative) retention times become increasingly irrelevant as N increases. 

This criterion may be used during a sequential optimization process (see chapter 5), leading to an acceptable result and to completion of the optimization process once the threshold value has been reached. Alternatively, it may be used to establish ranges of conditions in the parameter space for which the result will be acceptable. This latter approach has been followed by Glajch et al. [415], by Haddad et al. [424] and by Weyland et al. [425] and was referred to as resolution mapping by the former. Within the permitted area(s) secondary criteria are then required to select the optimum conditions. For example, the conditions at which the k value of the last peak (k is minimal while the minimum value for Rsexceeds 1 may be chosen as the optimum. Such a composite criterion can be described as... 

According to the station measurements, the information threshold has been exceeded on 17 days in the period depicted in Fig. 18.2a. Note that 16 of these exceedances were forecasted correctly. The alert exceedance predicted for July 21 was not observed but the measured values were just below the threshold value. The daily maxima above the alert threshold which were observed on 27-28 July 2006, were not predicted by the model. On these days, local peak emissions obviously caused a sudden and local increase of ozone concentrations around noon for 1-2 h. 

As Q increases, the two Gaussians shift toward x = 0 and are merged into a single distribution which peaks at x = 0 when Q reaches the threshold value Qi-... 

The procedure for establishing atomic connectivities in contour plots is relatively straightforward. It should be remembered, however, that these plots can be deceiving. Threshold values, which are essential for removing baseline noise from contour plots, may be sufficiently high also to eliminate smaller cross peaks. For this reason, it is recommended that cross sections through the individual frequencies of specific resonances be examined on the... 

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