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Tomographic reconstruction of tracer gas concentration profiles in a room with the use of a single OP-FTIR and two iterative algorithms: ART and PWLS.

Authors
Park-DY; Fessler-JA; Yost-MG; Levine-SP
Source
J Air Waste Manage Assoc 2000 Mar; 50(3):357-370
NIOSHTIC No.
20029860
Abstract
Computed tomographic (CT) reconstructions of air contaminant concentration fields were conducted in a room-sized chamber employing a single open-path Fourier transform infrared (OP-FTIR) instrument and a combination of 52 flat mirrors and 4 retroreflectors. A total of 56 beam path data were repeatedly collected for around 1 hr while maintaining a stable concentration gradient. The plane of the room was divided into 195 pixels (13 x 15) for reconstruction. The algebraic reconstruction technique (ART) failed to reconstruct the original concentration gradient patterns for most cases. These poor results were caused by the "highly underdetermined condition" in which the number of unknown values (156 pixels) exceeds that of known data (56 path integral concentrations) in the experimental setting. A new CT algorithm, called the penalized weighted least-squares (PWLS), was applied to remedy this condition. The peak locations were correctly positioned in the PWLS-CT reconstructions. A notable feature of the PWLS-CT reconstructions was a significant reduction of highly irregular noise peaks found in the ART-CT reconstructions. However, the peak heights were slightly reduced in the PWLS-CT reconstructions due to the nature of the PWLS algorithm. PWLS could converge on the original concentration gradient even when a fairly high error was embedded into some experimentally measured path integral concentrations. It was also found in the simulation tests that the PWLS algorithm was very robust with respect to random errors in the path integral concentrations. This beam geometry and the use of a single OP-FTIR scanning system, in combination with the PWLS algorithm, is a system applicable to both environmental and industrial settings.
Keywords
Analytical-methods; Optic-system; Infrared-spectroscopy; Visual-images; Computers; Industrial-hygiene; Workplace-monitoring; Mathematical-models; Laboratory-testing; Simulation-methods; Mathematical-models
Contact
Environmental & Indust Health University of Michigan 1420 Washington Heights Ann Arbor, MI 48109-2029
CODEN
AIWAE2
Publication Date
20000301
Document Type
Journal Article
Funding Amount
1353157
Funding Type
Grant
Fiscal Year
2000
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-02666
Issue of Publication
3
ISSN
1096-2247
Priority Area
Grants-other
Source Name
Journal of the Air and Waste Management Association
State
MI
Performing Organization
University of Michigan at Ann Arbor, Ann Arbor, Michigan
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