Diameter volume median

Median Diameter. The median droplet diameter is the diameter that divides the spray into two equal portions by number, length, surface area, or volume. Median diameters may be easily determined from cumulative distribution curves. 

The mass median diameter (MMD) is the most common descriptor of primary particle size and may be determined by sieving or centrifugal sedimentation. The volume median diameter, as determined by laser diffraction, may be used as an approximation of MMD, provided that the particle density is known and does not vary with size, and that the particle shape is near spherical. The MMD of a powder can be used as a predictor of aerodynamic diameter by Eq. (1),... 

A Grumman Avenger TBM flying approximately 20 m above the forest canopy applied the dyed spray with an emitted volume median diameter (vmd) close to 100 p. The spray mix, an aqueous fenitrothion emulsion, was applied at a rate equivalent to 1.5 1/ha and had a residual volume of 20% after evaporation of the water. Consequently, the evaporated vmd was approximately 58 p. 

Mass (Volume) Median Diameter The diameter that divides the mass (or volume) of the spray into two equal halves. One half of the mass is made up of droplets smaller than this diameter, and the other half of diameters that are larger. 

Figure 1 shows the variation in volume median diameter of drops formed from a typical hollow-cone nozzle (Spraycone WG 4008) with increase in viscosity from 1 to about 100 cp. To maintain a constant emission rate, the operating pressure was increased as the viscosity was increased. The variation of drop size with viscosity is similar to that already reported using fan-jet nozzles (II), and the results can be considered in terms of three viscosity ranges ... 

Mass median diameter will be the same as volume median diameter (since particle density cancels in computing the means). Thus we can use the Hatch-Choate relationship directly ... 

Figure 4a clearly shows that the fraction of cubic ice varies strongly with droplet volume median diameter, with smaller droplets freezing to more cubic ice than larger droplets. In fact, droplets with [Pg.421]

The droplets in this study typically had volume median diameters of around 10 pm. In a typical experiment droplets of the desired concentration and composition were cooled from ambient temperatures at a rate of 10 K min to 173 K where a diffraction pattern between 19 and 50° was measured. The intensity ratio I44/ I40 as a function of droplet freezing temperature, determined from the diffraction patterns measured in these experiments, has been reported previously. In Figure 6 we report the fraction of cubic ice as a function of droplet freezing temperature for each of the solute systems, determined using the relationship described in Figure 4. 

Plotting the surface and volume distributions of a log-normal aerosol distribution on a log-probability graph would also result in straight lines parallel to each other (same standard deviation). For the distribution shown in Figure 8.8 with Dpg = 1.0 pm and ag = 2.0, the resulting surface area and volume median diameters are approximately 2.6 pm and 4.2 pm, respectively. 

Volume median Diameter below which one-half... 

Therefore if the number distribution n/ (Dp) is log-normal, the volume distribution nviDp) is also log-normal with the same geometric standard deviation as the parent distribution and with the volume median diameter given by... 

Volume median diameter (VMD) That diameter where 50% of the particle volume is above and 50% below the diameter. 

Figure 8 Correlation between the volume median diameter of a nebulized aerosol, measured by laser diffraction, and thoracic deposition expressed as percent of total body deposition. The 95% confidence intervals represent the variability between volnnteer groups and not true intersubject variability. (From Ref. 3.)...

Note d 2 the Sauter mean diameter defined as the arithmetic mean of several measurements of the Sauter diameter SD (SD = 6 V/A with V the volume and A the surface area of the particle), d, the volume median diameter, which refers to the midpoint droplet size (mean), where half of the volume of spray is in droplets smaller and half of the volume is in droplets larger than the mean, p, p, and a, respectively the density, the viscosity, and the surface tension of liquid, D, the diameter of the disk, Q, the flow rate, and o> the angular speed of the disk. 

The median diameter corresponds with the 50 % value of a cumulative number, volume or mass percent distribution as function of the diameter. Fifty percent of the volume (number or mass) of the aerosol is in larger, and 50 % is in smaller particles than the median diameter. For a volume distribution it is the volume median diameter, for a mass distribution the mass median diameter. When the mass percent is expressed as a function of the aerod3mamic diameter, reference can be made to the mass median aerodynamic diameter (MMAD). 

The grade of kaolin employed is selected so that the volume median diameter is greater than about 2 microns and less than about 10 microns. Depending on the physical and biological properties of the particular active ingredient, the Irnal concentration of pesticide in granules can be as low as 10% w/w or as high as 80% w/w. 

Figure 3 Measured volume-size distribution showing fine-mode and coarse-mode particles and the nuclei and accumulation modes within the fine-particle mode. DGV, geometric mean diameter by volume equivalent to volume median diameter, and Og, geometric standard deviation, are shown for each mode. Also shown are transformation and growth mechanisms (e.g., nucleation, condensation, and coagulation). (From Ref 138.)...

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