Document Detail


Is an impedance operator necessary causal, and is this an issue of complexity?
MedLine Citation:
PMID:  19063324     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
An impedance operator describes the mapping of a velocity field across a part of a boundary surface, to the traction field across the same part. Understood to represent the solution of a "direct" problem, i.e., the velocity field describes the problem forcing and the traction field part of the solution, the impedance operator is necessary causal. On the other hand, understood to represent the general solution of an "inverse" problem, i.e., the velocity field is part of the observed solution with the traction field representing the problem forcing, the operator need not be causal. Continuing, a uniqueness theorem that applies to the direct problem assures that the impedance operator thusly defined is unique. The lack of a corresponding theorem for the inverse problem suggests that the impedance operator thusly defined need not be unique. This further suggests requiring causality selects from multiple impedance operators, representing multiple solutions to the inverse problem, the one that is unique. This raises two questions. Is the causality that makes the operator unique a requirement of the governing physics? What impact does this have on the concept of impedance as a tool for addressing complexity in dynamical systems?
Authors:
John J McCoy
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of the Acoustical Society of America     Volume:  124     ISSN:  1520-8524     ISO Abbreviation:  J. Acoust. Soc. Am.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-12-09     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7503051     Medline TA:  J Acoust Soc Am     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2555     Citation Subset:  IM    
Affiliation:
School of Eng., The Catholic Univ. of America, Washington, DC 20064.
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