Evaluation of virtual source beam configurations for rapid tomographic reconstruction of gas and vapor concentrations in workplaces.
J Air Waste Manag Assoc
; 47(5): 582-91, 1997 May.
Article
em En
| MEDLINE
| ID: mdl-9155247
ABSTRACT
Beam path average data from an Open Path Fourier Transform Infrared (OP-FTIR) spectrometer can be used to reconstruct two-dimensional concentration maps of the gas and vapor contaminants in workplaces and the environment using computed tomographic (CT) techniques. However, a practical limitation arises because in the past, multiple-source and detector units were required to produce a sufficient number of intersecting beam paths in order to reconstruct concentration maps. Such a system can be applied to actual field monitoring situations only with great expense and difficulty. A single monostatic OP-FTIR system capable of rapid beam movement can eliminate this deficiency. Instead of many source and detector units, a virtual source arrangement has been proposed using a number of flat mirrors and retroreflectors to obtain intersecting folded beam paths. Three virtual source beam configurations generated for a single-beam steerable FTIR system were tested using 54 flat mirrors and four retroreflectors or 54 flat mirrors and 56 retroreflectors mounted along the perimeter walls of a typical 24- x 21-ft test room. The virtual source CT configurations were numerically evaluated using concentration maps created from tracer gas concentration distributions measured experimentally in a test chamber. Synthetic beam path integral data were calculated from the test maps and beam configurations. Computer simulations of different beam configurations were used to determine the effects of beam geometry. The effects of noise and peak reducing artifacts were evaluated. The performance of the tomographic reconstruction strategy was tested as a function of concentration and concentration gradients.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Monitoramento Ambiental
/
Poluição do Ar em Ambientes Fechados
/
Local de Trabalho
/
Gases
Idioma:
En
Revista:
J Air Waste Manag Assoc
Assunto da revista:
SAUDE AMBIENTAL
Ano de publicação:
1997
Tipo de documento:
Article
País de afiliação:
Estados Unidos