Knowledge-based procedures

The Hierarchical Approach developed in this chapter incorporates a knowledge-based procedure for the synthesis of separations. This consists of dividing the separation section in three subsystems gas vapour, liquid and solid separations. Each subsystem is further managed by selectors, which makes use of unit operations. Split sequencing is based mainly on heuristics, although may include algorithmic or optimisation techniques. This chapter describe in more detail the synthesis of distillation trains for zeotropic distillations, the non-ideal case being left for the Chapter 9. 

Despite the drawbacks of chemical-fixation based procedures [21,24], most of our current knowledge on biological ultrastnicture relies on this approach. In contrast to cryopreparative procedures, chemical fixation does not require special skills and instrumentation. 

The knowledge base is essentially two-fold on one hand it consists of a series of procedures for calculating all-important physicochemical effects such as heats of reaction, bond dissociation energies, charge distribution, inductive, resonance, and polarizability effects (.see Section 7.1). The other part of the knowledge base defines the reaction types on which the EROS system can work. 

In the case of the CPI, there are relatively few situations where control room workers are likely to face continuous periods of overload. However, when overload does occur it is likely to be associated with situations when the plant is in an unusual or abnormal state for which the workers may not have any rules or procedures available. In these situations, knowledge-based processing (see Section 2.6.2), which needs considerable mental resources, will be required and errors of diagnosis are likely to occur. 

Performance problems may be exacerbated during unfamiliar or novel process events, for example, situations not covered in the emergency procedures or in refresher training. These events require knowledge-based information processing for which people are not very reliable. The types of errors associated with knowledge-based performance have been discussed in Chapter 2. 

Detailed procedures will only be required in unusual situations where the usual rules of thumb do not apply and the worker is likely to be in the knowledge-based mode. In Chapter 4, and case study 3 in Chapter 7, a systematic framework for developing procedures, in which their format and content is based on a detailed analysis of the tasks to be performed and the normal skill level of the person who will perform the tasks, will be described. 

If possible, the best procedure for selecting a tool is to implement a smaller test knowledge base similar to the final knowledge base in a few different tools. This test knowledge base should be small enough to be implemented quickly in different tools. On the other hand, it must be specific enough to highlight the differences between the tools. 

The Knowledge Base. The knowledge base holds symbolic knowledge. To be sure, the knowledge base can also contain tables of numbers, ranges of numerical values, and some numerical procedures where appropriate. But the major content consists of facts and heuristics. 

Computational efficiency. The efficiency of inference is enhanced by program and knowledge-base structure and by machine speed. Also, heuristic procedures, as used by experts, can augment the deductive procedures of conventional inference. 

Such a system would include a program similar to that of Storer and Comish-Bowden to do equilibrium calculations. A communication-control subprogram would be Hiked to an expert model by using the EXPERT knowledge-base shall (or system-builder) which is advantageous here because it can interact with procedures such as those written in FORTRAN for numerical computation. Additional programs and a small data base, which EXPERT can handle, would keep track of which chemical was what array element, and other requirements mentioned above. 

We have not attempted to make the computer do the job of auto-r matically finding the fundamental laws of chemistry from a compilation of individual facts. Rather, we have explicitly built into the computer specific models that we believe can represent the structure of chemical information. We were guided in this endeavor by concepts derived by the chemist and have tried to develop models and procedures that quantify these concepts. In doing so we have put more emphasis on the acquisition and representation of knowledge than on problem-solving techniques. In any expert system the quality of the knowledge base is of primary and desicive importance. 

The knowledge base of that part of the EROS system that predicts chemical reactivity consists of the procedures for calculating the physicochemical effects and the way in which they are connected. 

The author and the publisher of this Work have made every effort to use sources believed to be reliable to provide information that is accurate and compatible with the standards generally accepted at the time of publication. Because medical science is continually advancing, our knowledge base continues to expand. Therefore, as new information becomes available, changes in procedures become necessary. We recommend that the reader always consult current research and specific institutional policies before performing any clinical procedure. 

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