微粒沈積均勻度量測與應用(1/3)
Other Title
DETERMINATION OF UNIFORMITY OF FILTER DEPOSITS
Date Issued
2005-07-31
Date
2005-07-31
Author(s)
DOI
932211E002034
Abstract
Certain measurement techniques (such as the asbestos method using phase
contrast microscopy) require uniform deposits of the sample on a filter. The asbestos
fiber analytical methods require such uniform deposition because the analysis only
observes small, randomly chosen locations on the filter. The adequate number of total
counting fields and other counting protocols (such as equal distance and equivalent
area) still require further study. Moreover, the classification and characterization of
the uniformity (or non-uniformity) of filter deposits remains poorly defined. Sampling
for asbestos and other fibers is currently conducted with a 25-mm diameter filter
cassette and a 50-mm long straight tubular inlet, called a cowl.
In this study, a vibrating orifice monodisperse aerosol generator was used to
generate methylene blue particles. The aerosols were dried by filtered compressed air
and then neutralized by inducing a charge on the droplet stream that emerged from the
vibrating orifice. An Aerodynamic Particle Sizer was used to measure the number
concentration and size distribution of the generated aerosol particles. Meanwhile, the
filter deposits were examined via image processing, combined with statistical
methods for defining uniformity.
In order to better define uniformity and make the indicator more universal, the
uniformity was defined as the exponential of the negative CV (coefficient of variation)
value which was a transformation for easily understanding the uniformity of the filter
deposits. The experimental results demonstrated that, when aerosol counting was
performed, the equivalent area approach was superior to the equivalent distance
approach.
Subjects
fiber counting
image processing
equivalent area
uniformity
Publisher
臺北市：國立臺灣大學公共衛生學院職業醫學與工業衛生研究所
Type
report
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