Stability analysis using describing function

Stability Analysis Using the Describing Function Approach... 

However, the general stabihty criterion is vahd even if these assumptions are removed. In fact, this stabihty criterion is valid for any linear control system (comprised of linear elements described by transfer functions). By contrast, for nonlinear systems rigorous stability analyses tend to be considerably more complex and involve special techniques such as Liapunov and Popov stability criteria (Khalil, 2001). Fortunately, a stability analysis of a linearized system using the techniques presented in this chapter normally provides useful information for nonlinear systems operating near the point of linearization. 

From the resulting reactions a set of coupled differential equations can be derived describing the deactivation of P, L and PI and the reaction rate constants can be derived from storage stability data by the use of parameter estimation methods. The storage stability data give the concentration of P+PI (it is assumed that the inhibitor fully releases the protease during analysis due to fast dynamics and the extensive dilution in the assay) and L as a function of time. 

The requirements for validation of CE instrumentation have been described. Although these are broadly similar to the requirements for validation of any instrumentation used in GLP/GMP-compliant laboratories, some aspects are peculiar to CE, especially in regard to OQI PV testing. Those features of a CE instrument which should be tested in an OQ/PV include temperature and voltage stability, detector function and injector precision. These should be directly assessed and not inferred from other measurements dependent upon one or more of these parameters or upon chemistry. It is important that the contributions to the performance of an analysis... 

To evaluate the hydrolytic stability of the resin samples, thin layers of the liquid resins were aged at 60°C and 96% relative humidity. The resins were sampled periodically and HPLC was used to monitor the formation of hydrolysis products as a function of aging time. The HPLC operating parameters were similar to those described previously for reverse phase analysis except for the mobile phase conditions which are shown below ... 

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