| Summary: | 碩士 === 長榮大學 === 職業安全與衛生學系碩士班 === 102 === The size of an aerosol particle significantly affects the dynamic and capture properties of the particle. Therefore, analysis of particle size distribution is an essential task in the study of an aerosol sample. Currently, the Solver tool in Microsoft's Excel spreadsheet software can be employed to perform a nonlinear regression and determine a size distribution function which has the sum of least square error or maximum likelihood to a given distribution pattern. Hence, the fraction and distribution parameter of each component in an aerosol mixture can be determined. This method has been assessed successfully with the aerosol generated in the laboratory.
This study concerned the effects of bin width and sizer range to the distribution parameters, such as CMD （Count Median Diameter）and geometrical standard deviation, determined by the nonlinear regression. The aerosol generated in the laboratory was analyzed by an aerodynamic particle size and the distribution was determined. The size bins were grouped and truncated to simulate the phenomena of greater bin width and the under-coverage. The size distribution was assumed to be log-normal. The methods included the sum of least square error on distribution function, fraction, and cumulative fraction, as well as maximum likelihood.
The results showed that the bin width should be smaller than the particle diameter geometrical standard deviation for an accurate determination of the distribution parameters. This result is independent on the method to be used. This study also showed the least square error on the fraction and cumulative fraction distributions are suitable for the determination of the distribution parameters when the particle size is partially covered by a particle sizers. However, the fraction of the particle to be covered by the sizer should be greater than 40 to 60%. The former lower limit is valid while the particle fraction below the sizing range is available; the latter is valid while the particle fraction outside the sizing range is totally unavailable.
The results of this study can provide a post-processing method to overcome the limitation of apparatus and sampling.
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