Hai Du

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The acquisition of knowledge is a key phase in the implementation of expert systems yet represents a significant bottleneck. An explanation-based method was applied to knowledge compilation in a GC diagnostic system. A package of macros for Microsoft Excel, MATRIX, was then developed to enable domain experts to build rule-based knowledge bases for expert systems. The MATRIX macros can be used as domain-oriented knowledge acquisition tools that are specialized in coding knowledge concerning the diagnosis of faults in analytical instruments. These knowledge acquisition tools do not require formulation of any certainty factors to resolve conflicts and enable experts in analytical chemistry to develop diagnostic systems without the direct help of a knowledge engineer. Using a statistical analysis method, information about the least frequency of each symptom in the domain knowledge matrix can be used to differentiate one cause from the others, ensuring that each cause is characterized sufficiently.;An expert system with a user-friendly interface has been developed to aid in the diagnosis of faulty analysis by gas chromatography. The system advises users on the identity of faulty components and the possibility of improper operation based on the appearance of the chromatograms that result from the experiment. The user can enter observations easily using a powerful new graphical-based interface.;The evaluation of the chromatogram produced during gas chromatography of a standard test mixture is of importance in the assessment of the performance of the underlying GC system. Therefore, an algorithm for automation of peak identification during the standard test was developed, which is partly based on information theory and chemical knowledge about the standard test mixture. The algorithm may be used to identify highly distorted peaks, including regular peak retention time shifts, missing peaks, and irregular peak retention shifts. Also, a knowledge-based system has been developed for automation of the quality control and diagnosis of a GC instrument. Relative performance indices are derived that relate instrument response to the chemical or physical properties of the samples of interest. The system can be used to detect faulty components in a GC system and trace changes that occur in the system.



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