Reliability modeling

Static reliability models are used in preliminary analyses to determine necessary reliability levels for subsystems and components. A subsystem is a particular low level grouping of components. Some trial and error is usually necessary to obtain reasonable groupings for any particular system. Early identification of potential system weaknesses facilitates corrective action. 

A. Amendola, Uncertainties in Systems Reliability Modeling Insight Gained Through European Benchmark Exercises, Nuclear Engineering and Design, Vol. 93, Elsevier Science Publishers, Amsterdam, Elolland, 1986, pp. 215-225. 

Maliadevaii, S. 1997 Physics-Based Reliability Models. In Cruse, T. A. (ed.), Reliability-Based Mechanical Design. NY Marcel Dekker. 

There are two reliability modeling codes used for Tech. Spec, modification to address time-dependent failure rate and repair FRANTIC developed by BNL/NRC and SOCRATES developed by BCl,/EPRI. 

HCR Human Cognitive Reliability model EPRIRP-2I70-3, 1984... 

Fleming, K, N cs al., 1975, A Reliability Model for Common Mode Failures In Redundant Safety Systems, Proceedings of the Sixth Annual Pittsburgh Conference on Modeling and Simulation, April. 

Reliability Data Processing, 4) Safety and Reliability Assessment, 5) Data and Uncertainties, 6) Human Reliability, 7) Reliability Modelling and Techniques, 8) Reliability Feedback in Systems Design and Operation, 9) Intelligent Interfaces for Data Retrieval. 

There are other distributions that can be used in a variety of reliability models. The Poisson, the extreme value, gamma, binomial, and Rayleigh distributions are sometimes used in specialized models. 

I am conscious that I have missed many sets of acronyms from my guided tour of the differential overlap models, and I will just tell you that MINDO, MINDO/1, MINDO/2 all appeared but have now been consigned to oblivion. With MINDO/3, Dewar thought that he had at last developed a reliable model for use by organic chemists. The abstract to the landmark MINDO/3 paper is terse ... 

Thus it is important to obtain reliable models for catalyst deactivation and to investigate, whether it is possible to decouple the deactivation model from the kinetic model or if it is necessary to treat the catalyst deactivation as one of the surface reactions on the catalyst [45]. 

An alternative approach is to replace an accurate but expensive first-principle-based technique by a reliable model potential. Such potentials, broadly referred to as molecular mechanics (MM), generally cannot account for bond-breaking, but can, in principle, account for the range of intermolecular interactions. However, using a fitted pair-wise potential may result in losing quantitative accuracy, predictability, and the underlying physics. 

Reliable Model ZX-QR-INST Pendent Horizontal Sidewall Quick Response Institutional Sprinkler, Reliable Automatic Sprinkler Co., Inc., http //www.reliablesprinkler.com/sprinklr/137c.htm... 

The importance of drug ionization in the in vitro prediction of in vivo absorption has been discussed [34], When the apical pH used in Caco-2 studies was lowered from 7.4 to 6.0, a better correlation was obtained with in vivo data, demonstrating that careful selection of experimental conditions in vitro is crucial to have a reliable model. Studies with Caco-2 monolayers also suggested that the ionic species may contribute considerably to overall drug transport [35],... 

In order to obtain reliable models (minimize the probability of chance correlations) it is necessary to consider the ratio /Jdf/v ... 

The minimum value of /Jdf/v required for a reliable model depends on the quality of the determination of the data to be correlated. The smaller the experimental error in the data, the smaller the value of /Jdf/v required for dependable results. Experience indicates that in the case of chemical reactivity data /Jdf/v should be not less than 3. For bioactivity studies /Jdf/v depends heavily on the type of data for rate and equilibrium constants obtained from enzyme kinetics a value of not less than 3 is reasonable while for toxicity studies on mammals at least 7 is required. 

Given a specific application, we might also include precipitation kinetics in our calculations, as described in Chapter 16. Wat et al. (1992) present a brief study of the kinetics of barite formation, including the effects of scale inhibitors on precipitation rates. For a variety of reasons (see Section 16.2), however, it remains difficult to construct reliable models of the kinetics of scale precipitation. 

In connection with practical situations where CO oxidation is important, we must also consider the perennial question of how to connect the low pressure results onto those at high pressure. Qualitatively this has been done for the CO oxidation reaction but it would still be worthwhile to attempt a numerical prediction of high pressure results based on low-pressure rate parameters. A very nice paper modeling steady-state CO oxidation data over a supported Pt catalyst at CO and O2 pressures of several torr has very recently appeared (.25). Extension of this work to other systems in warranted and, even though unresolved questions continue to exist, every indication is that the high and low pressure data can be reliably modeled with the same rate parameters if no adsorption - desorption equilibria are assumed. 

Fast and reliable modelling of the accident impact, not only a major accident but also of chemical terrorism, is important for early and correct protection of the affected community, from warning through protection to treatment. 

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