Number median size

It is also necessary to choose the position number and size of sensors to sample the magnetic field with accuracy. As the radial component of this field is null in the median plan of the excitation coil when no flaw is present, it seems obvious to measure this component, so we can use large gain amplifiers, figure 1 shows the typical aspect of the magnetic field for a ponctual flaw when a very long excitation coil is used ... 

Published results on the concentration and size distribution of small particles in mainstream smoke vary widely, with concentrations ranging from 107 to 1011 cm-3 and with NMAD (number median aerodynamic diameter) ranging from 0.2 to 0.7 fim (Ishizu et a/., 1978). The MMAD (mass median aerodynamic diameter) of undiluted mainstream smoke particles ranges between 0.93 and 1.00 finl (Langer and Fisher, 1956 Holmes et a/., 1959). Lower values of the MMAD for diluted mainstream smoke, which decreased with degree of dilution, are reported by Hinds (1978). However, the particle size distributions for mainstream smoke appear to have little relevance to its retention and distribution in the lung, for reasons discussed below. Note that the concentration of tars in mainstream smoke is about 1,000 times that of air in smoke-filled rooms. 

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. 

The average amount of suspended matter in the air during the winter months in the 14 cities in which the studies were made was found to be 5.1 mg per 10 cu m of air, of which 65 percent consisted of carbonaceous matter, 35 percent of ash, 12 percent of silica, and 2 percent of iron oxide. An average amount of 0.73 mg of sulfur was found to be present in 10 cu m of air during the winter months. The amount of sulfur in the air was found to be closely correlated with the amount of carbonaceous matter present. The modal size of the dust particles in the air was found to be about half a micron. The median size of the dust particles was found to be 0.58 m- Only a small percentage of the particles were more than iy2 ju in diameter. The variation in particle-size from city to city was found to be very small. The average number of particles per cu cm in winter was 815. 

Aerosol size has an effect on the lung dose. Fine particles breathed through the mouth or the nose from lOOnm to 1,000 nm median size had 5-20 nGy per becquerel. Below 100 nm, this number more than doubled at 25-65 nGy per becquerel at 20 nm median size. Median sizes had an approximate geometric standard deviation of 2, so that the 95% confidence interval of particle sizes ranged from 0.25 to 4 times the stated median size. Very small particles deposited more efficiently in the airways. Lung cancer was related to radiation dose. These dose estimates are important determinants of lung cancer. 

Figure 5 shows the respective distributions of the two techniques plotted as cumulative percent by number against size. The two curves appear quite similar. The number median of the MgO data is 60 fxm. This result represents a less than 4% difference, which is a very favorable comparison. The MgO analysis indicates a broader distribution. This may be attributed to the limited range of the visibifity technique as previously noted. Owing to this limitation, any droplet larger than 94... 

The following method, proposed by Powers (1948) for use in the sugar industry, has mueh to be said in its favour for the size speeifieation of crystalline products. This method employs arithmetic-probability graph paper (one scale divided into equal intervals, the other marked off according to the probability integral) and provides a simple means of recording the crystal size distribution in terms of two numbers only - the median size (MS), and a statistical quantity the coefficient of variation (CV) expressed as a percentage. 

For the sake of aggregation, the median size of three different colloidal asphalts increased from sol type, to sol-gel type, to gel type. On the same weight basis, the nurtiber of particles that can pass tlirough the filter and stay at dispersion will decrease from sol types, to sol-gel types, to gel types of asphalt. Thus, from the derived Kof6 Law equation, the size distribution number of the gel type asphalts becomes smaller than the other two types. The results of this research are in agreement with the reduction observed in previous results. 

Follow a procedure similar to that of Example 2.4, in order to elaborate a histogram, a frequency curve, and an undersize cumulative percentage graph, and determine the median size of the powder (note that the particle size distribution obtained will be by number, while in Example 2.4 the particle size distribution obtained was by mass). 

Average Particle Size A powder has many average sizes hence it is essential that they be well specified. The median is the 50 percent size half the distribution is coarser and half finer. The mode is a high-density region if there is more than one peak in the frequency cui ve, the distribution is said to be multimodal. The mean is the center of gravity of the distribution. The center of gravity of a mass (volume) distribution is defined by. Xyw = X XdV/X dV where dV = X dN dV is the volume of dN particles of size X This is defined as the volume-moment mean diameter and differs from the mean for a number or surface distribution. 

An aerosol size distribution can, therefore, be described in terms of the count median diameter, d, and the geometric standard deviation, a These parameters were obtained from experimental data using a diffusion battery method (Busigin et al., 1980). A diffusion battery is an assembly of a number of cylindrical or rectangular channels. The relative penetration of aerosols through different sizes of diffusion batteries at specified flow rates allows the aerosol size distribution to be calculated. 

The mean values of the activity and aerosol median diameters together with the best estimate of the standard deviation, an, based on the total number of measurements made for each parameter, are listed in Table V. Figures 5-8 show representative size distributions ... 

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