Deposit distribution

In general, different sized particles may have different cycle time distributions and different mass deposition distributions in the spray zone. One approach would be to use small discrete size distribution increments and then to apply Eq. (12) to each size fraction. Inherent in this approach is the assumption that each particle size fraction acts independently. This assumption may not be valid, especially if different particles take different circulation paths within the bed. From the population balance approach, Randolf and Larson (1988) have suggested the use of an effective growth diffusivity coefficient to account for random fluctuations in growth rate. Thus Eq. (6) would be modified to give ... 

Koschinsky, a. 2008. Ferromanganese Nodule Deposits Distribution, Composition and Origin / International Symposium Shaping the Future Deep-Sea Minerals and Mining, (March 9-12, 2008), RWTH Aachen... 

Fig. 48. Experimental vanadium deposit distributions in a microporous catalyst (100 A micropore diameter/204 m2/g SA) macroporous catalyst (1300 A pore diameter/14.5 m2/g SA) and bimodal catalyst (120 A micropore, 25,000 A macropore diameters/200 m2/g SA) (Plumail e al., 1983).

The manner in which Ni and V sulfide deposits accumulate on individual catalyst pellets depends on the kinetics of the HDM reactions as influenced by catalyst properties, feed characteristics, and operating conditions. The dynamic course of deactivation of catalytic reactor beds is also determined by the kinetics of the HDM reaction. The lifetime and activity of a reactor bed are directly related to the details of the metal deposit distribution within individual pellets. This section will review deactivation behavior of reactor beds in light of our understanding of the reaction and diffusion phenomena occurring in independent catalyst pellets. Unfortunately, this is an area of research which remains mostly proprietary with too little information published. What has been published is generally lacking in detail for the same reason. 

Even if a complex mathematical description of the fine structure of pores were available, the use of such a model for the deactivation problem would encounter further difficulties. Detailed information on the nature of the deposit distribution in the fine structure would be required. This is currently beyond analytical capabilities. 

While catalytic HDM results in a desirable, nearly metal-free product, the catalyst in the reactor is laden with metal sulfide deposits that eventually result in deactivation. Loss of catalyst activity is attributed to both the physical obstruction of the catalyst pellets pores by deposits and to the chemical contamination of the active catalytic sites by deposits. The radial metal deposit distribution in catalyst pellets is easily observed and understood in terms of the classic theory of diffusion and reaction in porous media. Application of the theory for the design and development of HDM and HDS catalysts has proved useful. Novel concepts and approaches to upgrading metal-laden heavy residua will require more information. However, detailed examination of the chemical and physical structure of the metal deposits is not possible because of current analytical limitations for microscopically complex and heterogeneous materials. Similarly, experimental methods that reveal the complexities of the fine structure of porous materials and theoretical methods to describe them are not yet... 

Snowden, P. Andrews, W. Sufley, G., "Spray Deposit Distribution within Balsam Fir Crown", Report P-77-6, USDA Forest Service, NA Area, S PF, Upper Darby, PA., 1977. 

In this equation, all quantities are as described above and e is the energy deposited in the complex upon collision with the neutral reagent. The energy deposition distribution has been measured recently by measuring the kinetic energy of the reactants after collision, specifically for the Cr+(CO)6 complex discussed above [9]. This work finds that the distribution can be parameterized using n, Eq. (5), where n is the same parameter used in Eq. (3) ... 

A variant of talc retinopathy has been referred to as microtalc retinopathy. This appears as fine refractile deposits distributed in the superficial retinal layers of the... 

In more recent attempts to map the cellular distribution of cisplatin, Beretta et al. (50) incubated human ovarian cancer cells (A2780) with cisplatin concentrations of up to 100 xM for 30 minutes and observed electron dense spots, identified as large platinum deposits, distributed in the cell cytoplasm and nucleus. Additionally, it was observed that the platinum deposits made blunt contacts with the plasma membrane, which suggests that the cellular influx of cisplatin is through an endocytosis-independent manner that is consistent with the passive diffusion theory of cisplatin uptake (50). 

The thickness of the catalytic layer deposited on channel walls is very small The average varies typically from 10 to 150 p,m. The first approximation concerning the deposit distribution is that the layer is distributed uniformly around the channel periphery. This may be true if circular channels are considered. The typical cross section of the monolith channels is, however, square. In this case a significant nonuniformity in the washcoat thickness is often encountered (Fig. 6). The reason is that the liquid from which the... 

Fig. 16 shows representative scintigraphic images from both the DPI and the EHD pulmonary drug delivery device. It can be seen that the EHD pulmonary drug delivery device produced a uniform deposition distribution through the lung field with only... 

In order to check the resist thickness dependence on formation of very fine pitch dot arrays using 30 keV electrons, we calculated electron energy deposition distribution (EDD) using Monte Carlo simulation. As considering the EDD due to electron forward scattering (FS), at least, the miniaturization of the bit size, the deviation value is very crucial. The deviations calculated for PMMA are about 2 nm, about 3 nm and about 8 nm ata resist thickness of 15 mm, 70 nm and 200 nm, respectively. As the resist thickness decreases, the value becomes small. Therefore, we have to use resist films as thin as possible for very fine pitch arrays formation. 

Fig. 5 [86] shows an example of the mean unit spray content for drug and radioactivity for several study days using this labeled powder. Each bar of the graph represents a mean standard deviation of 10 unit doses. While the CV of the daily measurements for both dmg and radioactivity must be within specified limits, it should be understood that the mean daily level of radioactivity in the formulation or nominal dose of radioactivity varies as a function of the level of the specific activity available from the generator on the day of the study. This variability in the amount of radioactivity affects only the absolute dose of radioactivity inhaled and not the measured deposition distribution. Deposition results should be normalized to account for these differences, even for the small, day-to-day variability in the supply of radioactivity. 

High throwing power (Wagner number) is essential for uniform deposit distribution Customized cell design can provide uniform distribution (even in absence of high throwing power)... 

Computer Simulations Illustrating the Effects of Process Parameters on the Non-Uniform Deposit Distribution Due to Resistive Substrate... 

Fig 7 shows the effect of the current density on the deposit distribution under the influence of a resistive substrate. As expected the distribution is significantly more uniform at low current densities (e.g., 10 mA/cm2). As the current increases, the non uniformity appears to converge and not much difference is noted between the simulations applying 40 and 60 mA/cm2. 

Lundgren D, Damon E, Diel J, et al. 1981. The deposition, distribution and retention of inhaled 239Pu02 in the lungs of rats with pulmonary emphysema. Health Phys 40 231-235. 

Polivanova, A.I. (1981) Particulars of methane carbon and hydrogen sulphide sulfur isotopes vs. salt deposits distribution. Organic Geochemistry of oil, gas and organic matter in Pree-Cambrian. Moscow, Nauka, p. 208-214. (in Russian). 

Figure 2. Representation of the energy deposition distribution, Fq(E,9,x) and incident ion depth distribution R(E,e,x) expected for a several kilovolt ion incident on an average mass target.

The CP behavior analysis code PSYCHE [13] has been developed and verified with the measured radiation data to analyze the distribution of corrosion product in the primary cooling system. A radiation dose calculation code has been developed by INC, to analyze the CP deposition distribution along the piping and components of the primary cooling system. The build-up of CPs is shown in Fig. 19 together with the reactor operation time. The PSYCHE calculations agree with the measured values. 

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