Diameter geometrical mean diameters

The classification as a carcinogen need not apply to fibres with a length weighted geometric mean diameter less two standard errors greater than 6 pm Sodium dichromate Sodium dichromate dihydrate... 

Irani and Callis (Ref 14) used two parameters of the distribution of ground monocalcium phosphate (which follows the commonly used log normal distribution law) namely, Mg and Og, the geometric mean diameter and the geometric standard deviation, to evaluate the precision and accuracy of electro-formed sieves vs sedimentation as a reference procedure ... 

Geometric mean diameter and 4.7% 4.6% standard deviation between electro-formed sieves sedimentation... 

The foregoing close agreement of the geometric mean diameter and geometric standard deviation results indicates that accuracy evaluations were made on an absolute scale, and did not refer to some arbitrary scale... 

Another diameter of interest is the geometric mean diameter, dg. This is particularly useful if one wishes to compare the microscopic diameter with the one estimated by sieving, dg(see Fig. 3b). For microscopy data, dg can be obtained using the relationship... 

The geometric mean diameter can then be found from the antilogarithm of log... 

Fig. 11 Sieving data presented as a cumulative percentage undersize plot. The data were used to determine the geometric mean diameter of ethylcellulose microcapsules. (Adapted from Ref. 19.)...

An advantage of applying the log-normal distribution to atmospheric aerosols is that the value of the geometric standard deviation, crg, is the same for a given sample for all types of distributions—count, mass, surface, and volume. It is only the value of the geometric mean diameter that changes, depending on the... 

TABLE 9.3 Values of the Constant b in the Hatch - Choate Equations for Converting the Count Geometric Mean Diameter to Mass, Surface, or Volume Diameters... 

Table 9.3 gives the values of b to be used for converting the count geometric mean diameter to the other types of geometric or mean diameters, respectively. 

A word of caution is also in order with respect to assigning a particular particle to the fine or coarse particle modes. Since the size distributions can generally be described as log-normal, they do not have sharp cutoffs. A few particles at the top end of the fine mode distribution will have diameters larger than 2.5 [jlm and a few at the bottom end of the coarse mode will have diameters smaller than this. For example, as Lodge (1985) points out, for a coarse particle distribution with a geometric mean diameter of 15 fim and a geometric standard deviation of 3, about 5% of the particles will have diameters below the 2.5-gm fine particle cutoff. This may be responsible for observations that while Si and Ca dominate the coarse particle mode, they are also often found at significant levels in fine particles (e.g., see Katrinak et al., 1995). 

The data were obtained from the samples summarized in Table L The fallout samples were separated into particle-size classes by standard sieves for particles larger than 44p and by the Roller analyzer for particles smaller than 44fi. In the sequel the size classes are characterized by their geometric mean diameters. The larger size classes of the Tewa sample were separated mechanically under the microscope into spherical and irregular fractions. Very few spheres could be found below the 177-/x class. The ratio of active to inactive particles was measured auto-... 

Table 5—Method of Determining the Geometric Mean Diameter of 245 Particles Measured by Means of an Optical Micrometer...

The terms dg and ag are called geometric mean diameter and geometric standard deviation, respectively. 

Example 2.9 Given a lognormally distributed aerosol with a geometric mean diameter of 1.5 pm and a og of 2.3, what are the surface-area median diameter and the mass median diameter of this aerosol ... 

Geometric mean diameter - ds, (Jim Geometric standard deviation aK ... 

Example 2.6 Compute the geometric mean diameter dg and geometric standard deviation ag for the data given in Example 2.1. 

Example 8.6 An aerosol made up of unit-density spheres is lognormally distributed with a geometric mean diameter of 2.0 pm and a geometric standard deviation of 2.2. Calculate the respirable fraction of this aerosol as sampled by a sampler which follows the BMRC curve and a sampler which follows the ACGIH curve. 

For the case of a lognormal aerosol having a geometric mean diameter of dg and geometric standard deviation of ag,... 

In Prob. 5, what would be the implied geometric mean diameter if the geometric standard deviation were assumed to be 2.0 ... 

Substituting this relationship into equations (2.86) to (2.89) yields the equivalent relationships relating surface average sizes with the surface geometric mean diameter. 

The characteristic data of particles are given by the mode diameter (MD) as the most frequent size of a particle population, the geometric mean diameter (OMD) of the particles and the total number concentration (TNC) as the total amount of particles over the whole measured range. The TNC is based on the flue gas volume at a standard oxygen content of 13%. 

The combustion chamber of the moving grate boiler system was run over a wide range ofbum rates, starting from 150 kW up to 600 kW. The analysis of particle emissions such as particle diameter or total number concentrations (TNC) showed only little variations with the process parameters (Fig. 3). Similar to the 70 kW burner system, all test runs resulted in mode diameters most frequent size diameter) of 100 nm. The geometric mean diameter (GMD) has been analysed in the range of 90.45 nm up to 95.0 nm. The total number concentration (TNC) was between 2.8IE-i-7 and 5.12E-I-7, depending on excess air supply. 

Figure 2 presents the particle emission size distribution for Tests 2 and 4 measured with SMPS. It is possible to verify the presence of one only mode in the submicron size range, although other nanometric modes could exist below 0.01 micron. The detected mode is located in the 0.2 to 0.3 micron range, and its geometric mean diameter (GMD) is approximately 0.2 pm. Notice that, although the particle... 

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