For particle size distributions, the log-normal distribution is by zry67523

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									For particle size distributions, the log-normal distribution is commonly employed to fit data or
represent size distributions. This distribution has the form:

                                      1         1  ln(x) - ln( )  2 
                                                                     
                          f(x) =           exp                   
                                 ln( ) 2      2
                                                        ln( )      
By direct analogy with the previous arguments, we can write,
                                              ln(x) - ln(  )
                                        z =
                                                  ln( )
And the cumulative distribution for the log-normal distribution is then given by:
                                              1 1
                                     F(z) =     erf(z / 2)
                                              2 2
A gas-sampling probe for estimating a particle size distribution is shown in Fig. 7-1. A typical
problem encountered for this type of application is described later in this section.




                    Fig. 7-1. A cascade impactor particulate sampling probe.




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