Parameter drift

Zuppa et al.60 have used SOMs in the assessment of data from an electronic nose. Six chemicals—water, propanol, acetone, acetonitrile, butanol, and methanol—were presented at varying concentrations to a 32-element conducting polymer gas sensor array. The output was used to train a group of SOMs, rather than a single SOM, to avoid the problems of parameter drift. One SOM was associated with each vapor, and with suitable use of smoothing filters, the SOM array was found to perform effectively. 

Finally, on-line parameter estimation allows one to diagnose parameter drifts [12]. 

Unfortunately, the severity of the molecular ion overlaps can be more difficult to predict because the molecular ion signal magnitude can be very dependent on the sample composition (including solvent and acid), the extent of solvent loading, and instrument parameters. Drift in the polyatomic ion signals is often more severe than for elemental ions. 

We now have several questions to answer. What do we mean by an outbreak in the context of this model The idea must be that, as parameters drift, the bud-... 

Although setpoint drift is expected to be negligible because of digital protective systems, periodic surveillance tests designed to detect input parameter drift and setpoint changes are performed. In addition, automatic testing of the PPS bistable trip function is provided and PPS trip setpoints are monitored by the Data Processing System as described in CESSAR-DC, Sections 7.2.1.1.9 and 7.7.1.8.2.I. 

In the stress part of a qualification test the components are subjected to extreme environmental conditions over a longer period of time, to check v ether these conditions lead to parameter drift, aging and failures of components with time. EV the extreme environmental conditions aging phenomena are accelerated so that drifts and failures occur after a reasonably short time. However, it is inportant that no failure mechanisms are... 

The red arrows indicate that all parameter of functions could be incorrectly higher or lower. If the parameter drifts over time or oscillate or are sporadically wrong this could be considered in a more detailed analysis, after the first design steps and detailing of the functional behavior. 

A similar strategy may be adopted for hydrated cements. When analysing a hydration time series of a specific system, such as in Figure 4.13 for a zeolite-blended cement, all parameters of the anhydrous phases may be fixed except for the scale factors. The phase-dependent parameters of the hydration products should be allowed to vary as their stoichiometry and microtexture may change during hydration. This approach strongly limits parameter drift and is very instrumental in obtaining consistent trends in hydration studies. 

In the first step, C3S (M3) and C4AF were identified as major phases. Both phases were included in a first refinement cycle. Phase-specific parameters that were varied were the phase scale factors, lattice parameters and a Lorentzian peak-broadening parameter. To constrain parameter variation and prevent parameter drift, hard limits were placed on the variation intervals e.g. for lattice parameters a 1% variation from the literature values was allowed. The refined global variables were a specimen displacement error and a background polynomial of two coefficients and a 1/X term. The results of this first refinement round are shown in Figure 4.17a. The graph shows that the majority of diffraction peaks has been matched however, the difference curve clearly shows that many smaller peaks are not or not fully accounted for. 

In the final refinement round the results of the SAM residue analysis are integrated into the XRD analysis of the untreated cement. Phase-specific parameters, such as lattice and peak-broadening parameters, were kept fixed for minor phases refined in the SAM residue analysis. This measure is implemented to reduce the number of varied parameters in the final refinement and mitigates parameter drift risks. The comparison between the observed and final calculated patterns is given in Figure 4.17d. Clearly, over the subsequent analysis rounds, the fit to the observed pattern was much improved. At this stage, more... 

Several properties of the filler are important to the compounder (279). Properties that are frequentiy reported by fumed sihca manufacturers include the acidity of the filler, nitrogen adsorption, oil absorption, and particle size distribution (280,281). The adsorption techniques provide a measure of the surface area of the filler, whereas oil absorption is an indication of the stmcture of the filler (282). Measurement of the sdanol concentration is critical, and some techniques that are commonly used in the industry to estimate this parameter are the methyl red absorption and methanol wettabihty (273,274,277) tests. Other techniques include various spectroscopies, such as diffuse reflectance infrared spectroscopy (drift), inverse gas chromatography (igc), photoacoustic ir, nmr, Raman, and surface forces apparatus (277,283—290). 

Monitoring by Electromechanical Instrumentation. According to basic engineering principles, no process can be conducted safely and effectively unless instantaneous information is available about its conditions. AH sterilizers are equipped with gauges, sensors (qv), and timers for the measurement of the various critical process parameters. More and more sterilizers are equipped with computerized control to eliminate the possibiUty of human error. However, electromechanical instmmentation is subject to random breakdowns or drifts from caUbrated settings and requires regular preventive maintenance procedures. 

Fault detection is a monitoring procedure intended to identify deteriorating unit performance. The unit can be monitored by focusing on values of important unit measurements or on values of model parameters. Step changes or drift in these values are used to identify that a fault (deteriorated performance in unit functioning or effectiveness) has occurred in the unit. Fault detection should be an ongoing procedure for unit monitoring. However, it is also used to compare performance from one formal unit test to another. 

DL = drift loss, water lost from tower system entrained in exhaust air stream, measured as (a) % of circulating water rate, gpm, or (b) more precise [144], an L/G parameter and drift becomes pounds of water per million pounds of exhaust air for estimating ... 

Drift consists of base line perturbations that have a frequency that is significantly larger than that of the eluted peak. Drift is almost always due to either changes in ambient temperature, changes in solvent composition, or changes in flow rate. All these factors are easily constrained by careful control of the operating parameters of the chromatograph. 

The major unresolved questions for these systems are the coalescence and flocculation of particles under mechanical agitation and the parameters which influence copolymer composition drift. 

Subcase bl This case is encountered, for example, when batch records from different production campaigns are compared and the same number of samples was analyzed in each campaign. (Note under GMP, trend analysis has to be performed regularly to stop a process from slowly, over many batches, drifting into a situation where each parameter on its own is within specifications, but collectively there is the risk of sudden, global loss of control. Catastrophe theory has gained a foothold in physical and biological literature to describe such situations cf. Section 4.14.)... 

One of the calculation results for the bulk copolyroerization of methyl methacrylate and ethylene glycol dimethacrylate at 70 C is shown in Figure 4. Parameters used for these calculations are shown in Table 1. An empirical correlation of kinetic parameters which accounts for diffusion controlled reactions was estimated from the time-conversion curve which is shown in Figure 5. This kind of correlation is necessary even when one uses statistical methods after Flory and others in order to evaluate the primary chain length drift. 

We discuss some characteristics of the bifurcation diagram of the K-S for low values of the parameter a (for details see (7)). We will work in one dimension and with periodic boundary conditions. In what follows, we always subtract the mean drift... 

A similar equation can be derived for the slope, where P is the drift parameter ... 

Equations (41.12) and (41.13) can now be combined in a single system model which describes the drift in both parameters ... 

The model contains four parameters, the slope and intercept of the calibration line and two drift parameters a and p. All four parameters are estimated by applying the algorithm given in Table 41.10. Details of this procedure are given in Ref. [5]. 

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