Indicative particles classification

As can be seen from Table 19.3, the proportion of indicative particles exceeds the proportion of unique particles, even for promptly collected FDR. The higher proportion of indicative particles detected in casework is almost certainly due to particles from nonfirearm sources, particularly single primary element ones, meeting the criteria of the classification scheme. 

From casework statistics the unique particles (those containing the combination lead, antimony and barium, and those containing antimony and barium) occur in the ratio 7 3, respectively. Approximate percentages for indicative particles are lead-only 55% lead, antimony 20% lead, barium 8% antimony-only 7% barium, calcium, silicon 5% barium-only 5%. Table 19.3 gives an indication of the levels of the primary elements in each particle type. Table 19.4 gives an indication of the levels of accompanying elements in each particle type and is the basis for note b in Table 19.5, Particle Classification Scheme. 

The original particle classification scheme192 has been revised based on casework experience, research work on blank cartridges, and so forth, and a detailed analysis of 14 years of casework results. The particle classification scheme used in Northern Ireland since 1984 is given in Table 19.5. The indicative particles are in tentative order of decreasing significance. 

Figure 52 also shows that the actual recovery curve does not decrease below a certain level. This indicates that a certain amount of material is always recovered to the underflow and bypasses classification. If a comparison is made between the minimum recovery level of solids to the liquid that is recovered, they are found to be equal. Therefore it is assumed that a percent of all size fractions reports directly to the underflow as bypassed solids in equal proportion to the liquid split. Then each size fraction of the actual recovery curve is adjusted by an amount equal to the liquid recovery to produce the "corrected recovery" curve shown in Figure 52. As the Djoc point changes from one application to another, the recovery curves shift, along the horizontal axis. In order to determine a single graph which represents the corrected recovery curve, the particle size of each size fraction is divided by the Dj value and a "reduced recovery" curve can be plotted, as shown in Figure 53. Studies reported by Arterburn have shown that this curve remains constant over a wide range of cyclone diameters and operating conditions when applied to a slurry...

A particilarly powerful use of the classification results is in factor analysis. This will help to uncover interrelationships anong the particle types and will provide additional information for source attribution. The results of the factor analysis are also helpful for judging the significance of the cluster analysis, in that if the occupations of two similar particle types are uncorrelated over several samples then this indicates that the particle types and the clusters from which they are derived are significantly different. 

Fig. 2 Positional detection and mean-square displacement (MSD). (a) The x, y-coordinates of a particle at a certain time point are derived from its diffraction limited spot by fitting a 2D-Gaussian function to its intensity profile. In this way, a positional accuracy far below the optical resolution is obtained, (b) The figure depicts a simplified scheme for the analysis of a trajectory and the corresponding plot of the time dependency of the MSD. The average of all steps within the trajectory for each time-lag At, with At = z, At = 2z,... (where z = acquisition time interval from frame to frame) gives a point in the plot of MSD = f(t). (c) The time dependence of the MSD allows the classification of several modes of motion by evaluating the best fit of the MSD plot to one of the four formulas. A linear plot indicates normal diffusion and can be described by = ADAt (D = diffusion coefficient). A quadratic dependence of on At indicates directed motion and can be fitted by = v2At2 + ADAt (v = mean velocity). An asymptotic behavior for larger At with = [1 - exp (—AA2DAt/)] indicates confined diffusion. Anomalous diffusion is indicated by a best fit with = ADAf and a < 1 (sub-diffusive)...

The results calculated for the flight trajectories of particles with various diameters and moisture contents are shown in Fig. 6.22. The figure indicates that the radial gas flow exhibits certain classification effect for particles with various diameters. However, the moisture content of the particle has almost no effect on the flying distance. These theoretical results illustrate that the arrangement of the upper overflow discharging port is totally unfeasible. 

The goal of sideline extraction is to regain the starch (fine granules) that has been lost in the overflow of the classification. Figure 11.19 indicates that the particle sizes of starch and fiber are sufficiently different to enable separation by sieving. This is done by the same conical rotating sieves that were used in the fiber extraction, but with a... 

The term chemisorption was coined in order to classify the interaction between a particle in the gas phase and a solid surface, i.e. the result of the adsorption process [1]. If the interaction leads to the formation of a chemical bond the adsorbate formed is called a chem-isorbate. Where chemical bond formation is not important the process is classified as physisorption. There are several conceptual problems with such a differentiation which we briefly address in the following, and which indicate that a more detailed look at the entire process of adsorbate formation is needed before a reliable classification may be carried out. In fact, as it turns out, for a conclusive classification one would need the full theoretical and experimental understanding of the system under investigation. Such an approach must include the static aspects, i.e. the energies involved, as well as the dynamic aspects, i.e. the processes involved in the formation of the adsorptive interactions. 

Precipitated particles lead to an increase in UV absorbance due to light scattering. Lipinsky used a diode array UV (Hewlett Packard HP8452) at 600-820 nm for their experiment. UV absorbance (y-axis) vs. p,L DMSO plots (x-axis) is used to detect the precipitation point. A strong increase in the slope of the curve indicates precipitation. Precipitation defines the maximum solubility level in this experiment. The method allows a classification between poor, moderate and good... 

Cooper et al. (1994) have reported re-suspension studies on soils contaminated with plutonium during nuclear weapons tests by use of a mechanical dust-raising apparatus. Airborne dust was analysed in terms of mass and Am activities for particle sizes less than 7 pm. The AMAD was determined as 4.8-6 pm for re-suspended soil. Also, surface soil was characterised in the laboratory by means of sieving and microparticle classification, yielding mass and "Am activity distribution with respect to size. Data indicate the granularity of plutonium contamination at both major and minor trial sites. Depth profile analyses for undisturbed areas demonstrate that most (74% on average) of the americium and plutonium activity is found in the top 10 mm of soil. Plutonium and americium activities were found to be enhanced in the inhalable fraction over their values in the total soil, and the enhancement factors were similar in re-suspended dust and surface soil. Observed enhancement factors ranged from 3.7 to 32.5. 

From Table I, it can be seen that for a constant metal loading (5%), the sensitivity to SMSI of the present samples varies as Ni Pt>Rh, This classification is purely qualitative and not indicative of the proper influence of the nature the metal since several parameters such as texture and dispersion can influence the extent of SMSI, For Instance, nickel is under the shape of far larger particles than Pt or Rh ones with 2 to 3 times more atoms. On the contrary, in the case of Pt catalysts, the comparison between catalysts is more meaningful since the metal crystallite size is homodispersed... 

The distinct concepts, wave or particle, of 19th century physics are now inseparably mingled. Wave mechanics, so essential to our ideas now, would have been a contradiction in terms in the 19th century. The question of whether an electron, or a photon, is a wave or particle has lost all meaning. We can say with precision in what circumstances it is useful to treat the electron as a classical particle or the photon as a classical wave. We know when we must consider the wave aspects of the classical particles and the particle aspects of the classical wave. Any final classification into particle or wave would be artificial. Both particles and waves have a more general nature than their names indicate. We use the old names, fully realizing the more general character of the entity in question. 

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