Median size

The differential and eumulative size distributions are elearly related, as shown in Figure 1.9. Differentiating the eumulative distribution restores the original histogram but in a smoother form. Two important properties ean be defined, the modal and median sizes. 

The modal size is at the point of maximum frequeney on the differential distribution. The median size is at the 50 per eent point on the eumulative plot. Note that the modal size of a distribution is not neeessarily equal to the median. 

The mass median size (above and below which half the distribution lies) is given by... 

Rossiter (1986) demonstrated the procedure for the production process of crystalline common salt from brine. It was found that the optimal median size is determined by the entrainment limit in the crystallizer. The crystallizer had to be operated at maximum allowable temperature and the slurry density measured for quality constraints. It was also suggested that cost discontinuities should be imposed based on temperatures of the available heat sources, possible materials of construction and other intrinsic properties of the system. 

The values of a and Dmx are characteristic constants for a given size distribution. If a material follows a log-probability distribution on one basis (x), it also does on any other basis (y) - with the same value of the standard geometric deviation (a) but a different value of median size (Dmx) corresponding to the new basis (y). This is a unique property of log-propability distribution (See Eq 2) ... 

A graph paper based on this type of relationship can be obtained. It permits convenient graphical representation of size distribution data (as shown in Fig 3) even if the distribution does not follow a log-probability relationship. In addition, the assumption of a log-probability distribution as an approximation permits simple conversion from one basis of representing size distribution, mean size, or median size to another basis... 

IAEA/AL/095 1996). Both methods were suitable, but needed to be repeated several times to produce the small particle size that was required. The particle size reduction, e.g. of IAEA-395 from a median size of 30 pm to 3.5 pm, improved the homogeneity of elements. Sampling constants (the minimum mass that can be used to achieve a random error of i % at the 65 % confidence level) improved from a factor of 1.2 for Sc, up to a factor of 800 for Au. The average improvement was about a factor of 2-10. (Ni Bangfa et al. 1996). From these initial experiences, it is dear that preparation of reference materials is critical with respect to the final particle size distribution, which should exhibit a low maximum (<50 pm) and a narrow range in particle sizes. Milling techniques to meet such criteria are available today, and materials that show intrinsic uniformity are particularly suitable to achieve the desired properties. 

Based on 46 measurements, the activity median aerodynamic diameter of Pb-212 averaged 0.13 pm (0g = 2.97), while Pb-214 averaged 0.16 pm (Og = 2.86). The larger median size of Pb-214 was attributed to a-recoil depletion of smaller aerosols following decay of aerosol-associated Po-218. 

The Szego mill has been used for dry as well as wet grinding of coal, in both water and oil, for the preparation of coal-slurry fuels. To grind coal in water to the standard boiler size (80 per cent < 74 im) takes about 7 MJ/Mg (20 kWh/tonne). For micronized grinding, to a 15 xm median size, 2-3 passes through the mill are required and the specific energy... 

From Equation 5 (in Table I), the slope of CSD on R-R chart at the dimensionless median size, S is given by,... 

Mean + S.E. of the mean, calculated on the total number of mice per group (a non-tumor-beaiing mouse was counted as zero but incorporated into the calculation). The differences in median size of treated and control series were statistically significant (Student s t-test) at P < 0.05 unless for where P < 0.10 only. 

Lack of Economy in Size. Fine chemicals are manufactured in discrete campaigns in multipurpose plants. The reactor trains of these plants are similar throughout the industry. Regardless of the size of the companies, their main constituents, the reaction vessels, have a median size in the 4-6m bracket. Therefore, the unit cost per m per hour does practically not vary with the size of the company. 

The surface separation in the slit-shaped pore is determined by the crystal thickness. For an illite [a fine-grained mica with a surface area of 1.6 X 10 m per kg], the slit-shaped pores have a median size of about 5nm and in the overlap pores the surface separation is about Inm. The stability of day domains within a soil is a crucial feature for agricultural production because the permeability of a soil to aqueous electrolyte solutions depends on this stability. Swelling of these domains reduces permeability. 

The latter is dependent on interplay between the degree of permeability of the cell/tissue and the size of the probe. In practice, probes with a median size of 200-400 bp are suitable for cells/tissues fixed in aldehyde and subjected to varying degrees of proteolysis (see Section 3.). I have found that fixation of cells m aldehyde followed by mild proteolysis produces the best results. 

There are various kinds of polytetrafluoroethylene. One is granular polymer consisting of spongy, white particles having a median size of about 600/l The specific surface of this polymer is on the order of 2 m2/g (determined by nitrogen adsorption and calculations by the method of Brunauer, Emmett, and Teller). Since this specific surface area is about 1700 times the observed outer surface of the particles, these measurements confirm the porous, spongelike structure that can be seen in the photomicrograph of a cross section of several particles in Fig. la. 

Fig. 4 Key features of submicron aerosol measured at North European EUSAAR stations, (a) location of the stations, (b) histograms of the annual N30 5o concentrations, (c) seasonal median size distributions, and (d) seasonal N10o variation at Hyytiala, Finland...

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