Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Author: search.filters.author.Mavrovouniotis, Micheal L.Subject: search.filters.subject.mathematical modeling

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    Synthesis of Direct Mechanisms for Chemical Systems
    (1991) Mavrovouniotis, Micheal L.; ISR
    A chemical system consists of intermediate species, terminal species, and mechanism steps. Understanding the behavior of a chemical system can be significantly aided by the identification of mechanisms responsible for overall reactions which do not involve net consumption or production of reaction intermediates. Issues arising in the definition and identification of direct mechanisms, which are the shortest possible mechanisms, are discussed. In the context of examples of catalytic synthesis of ammonia and methanol, an alternative approach for the construction of mechanisms from steps is presented. An algorithm for the construction of direct mechanisms is then formally stated; the algorithm is based on successive processing and elimination of reaction intermediates which should not appear in the overall stoichiometry of the reactions accomplished by the mechanisms. Throughout the operation of the algorithm, irreversible steps are used only in their permitted direction. The basic algorithm may construct indirect or duplicate mechanisms, but variations of the algorithm are proposed which discard such redundant mechanisms. A number of hypothetical chemical systems illustrate the differences between the proposed algorithm and other approaches.
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    Computer-Manipulation of Conjugate Forms in Proper Estimation
    (1991) Mavrovouniotis, Micheal L.; Constantinou, Leonidas A.; ISR
    Physical and chemical properties of pure compounds and mixtures are essential for the analysis and design of chemical processing systems. A method for the estimation of properties of organic compounds from their molecular structure is presented, based on the contributions of Atoms and Bonds in the properties of Conjugate forms of a molecular structure (ABC). A real chemical compound can be considered the hybrid of a number of conjugates, which are alternative formal arrangements of the valence electrons of the molecule. The property-estimation method generates all conjugate forms of the molecule and assigns properties to each conjugate, simply by summing contributions from atoms and bonds in the particular electronic arrangement of the conjugate. The properties of the actual compound are then derived from the properties of the conjugates. The generation and analysis of conjugates is based on symbolic computation and Object-Oriented Programming (OOP). Atoms, bonds, molecules, electron pairs, and other entities can be represented as interconnected objects within OOP. The generation, comparison, and analysis of conjugates can be carried out through computer- based manipulation of the objects and their interconnections. One needs to encode operators which generate the conjugates, as well a rules for pruning the generation so that only the most important conjugates are considered. The nature and connectivity of atoms within a molecule determine the physical and chemical properties of the molecule. Traditional group-contribution methods eliminate much of the detailed molecular-structure information at an early stage of the property-estimation effort. Through symbolic computation and the concept of conjugation, the ABC approach aims to use molecular structure information more effectively.