Johnstone coefficient

Johnston, H.M. Gillham, R.W. "A Review of Selected Radionuclide Distribution Coefficients of Geologic Materials" TR-90 Atomic Energy of Canada Ltd Univ. of Waterloo, 1980. 

Transport Properties Although the densities of SCFs can approach those of conventional liquids, transport properties are more favorable because viscosities remain lower and diffusion coefficients remain higher. Furthermore, CO2 diffuses through condensed-liquid phases (e.g., adsorbents and polymers) faster than do typical solvents which have larger molecular sizes. For example, at 35°C the estimated pyrene diffusion coefficient in polymethylmethacrylate increases by 4 orders of magnitude when the CO2 content is increased from 8 to 17 wt % with pressure [Cao, Johnston, and Webber, Macromolecules, 38(4), 1335-1340 (2005)]. 

In a series of careful investigations, Johnston et al.282 285 have measured the initial rates of the N205 + N0 reaction as a function of temperature and of pressure of various additives. They have successfully interpreted the pressure dependence of the first-order rate coefficient, k42, in terms of the expression... 

Data on gas systems, again using a point source, have been obtained by Bernard and Wilhelm (B6), Dorweiler and Fahien (D20), Fahien and Smith (F2), and Plautz and Johnstone (P6). Plautz and Johnstone measured dispersion coefficients under isothermal and nonisothermal conditions and found that there was a difference between the two only for low Reynolds numbers. 

The first quantitative studies were made by Johnston and Crosby,227 228 who used a stopped-flow technique to monitor the disappearance of ozone by absorption of 2537-A light. Intensity was measured with a photomultiplier tube, the output of which was displayed on an oscilloscope with sweep frequency 0.2-2 sec. Corrections were made for the absorption of N204 at 2537 A, because the absorption coefficient of that species is almost 5% that of ozone at that wavelength. The reaction was observed at 198 and 230°K, with initial NO and 03 concentrations of 0.17-1.85 x 10-5 M and 0.27-2.13 x 10 5 M, respectively. Nitrogen was present in pressures of 130-650 torr. The primary step was determined to be a bimolecular second-order reaction... 

Fig. VI-7, (a) The absorption cross sections of N20 in the region 2100 to 2500 A. it is in units of cm2 molec"base e, room temperature. From H. S. Johnston and G. S. Selwyn Geophvs. Res. Lett. 2, 549 (1975). Reprinted with permission. Copyright by American Geophysical Union. (A)-(e) Absorption coefficients of NzO in the region 1080 to 2100 A. a is in units of atm" cm1, base e, 0 C. From Z.elikotf et ul. (1079), reprinted with permission. Copyright 1953 by the American Institute of Physics.

Fig. VII—21. (a) Absorption cross sections of HNOj in the region 1850 to 3350 A.. . a in units of cm2 molcc base e, room temperature. From Biaume (107) and Johnston. . Graham (539), reprinted by permission. Copyright 1973 by the American Institui< Physics. (A) Absorption coefficients of nitric acid in the region 1200 to 1700 A. < > .. ..

Wilkinson and Johnston record intensities in terms of the atmospheric absorption coefficient at 30° c. Their values have been multiplied by (22 4 x 3O3)/(2 30 x 273) in order to obtain molecular extinction coefficients. The present discussion assumes that the bands observed by them in the continuum are not due to impulines. There is some doubt of this, however, since Rathenau s findings arc not entirely in agreement with those of Wilkinson and Johnston. 

Exchange constants for low-dimensional magnets are most commonly obtained via comparison of experimental data to the predicted behavior of a thermodynamic property for a given model, usually the magnetic susceptibility. Johnston et al. showed that the molar susceptibility xm of the uniform chain can be expressed as a ratio of polynomials in powers ofthe reduced temperature t t = hgT/ 2J ). The coefficients N and D are listed in Table 1. 

The K-L model, because of its greater simplicity, thus seems to be the model of choice for systems with smaller bubbles. In this paper we shall show how the K-L model can be used to predict the experimental results obtained by Massimilla and Johnstone (1961) on the catalytic oxidation of ammonia. It will be seen that the performance of their system was largely controlled by reaction limitations within the bed s phases. The effects of various parameters on bed performance are examined for such a reaction-limited system, and then the effects of these parameters for a transport-limited system are also discussed. Finally, we consider the effect of using average values of the bubble diameter and transport coefficients on model predictions. 

More elaborate and more reliable procedures that can be used for estimates of rate coefficients of free-radical reactions are the bond energy-bond order method (BEBO) of Johnston and Parr [13] and the curve-crossing approach of Pross [14]. 

Benson " has calculated Ki 2 as described in section 1.1.1 and using this value together with the rate coefficient obtained by Johnston and Yost for (10) he estimated... 

Hinshelwood and Lindars re-examined the decomposition and found no evidence for a surface reaction as suggested by Johnston. They obtained an expression for the rate coefficient, viz. 

Kinetic isotopic effect studies of this kind permit a test of the mass dependence predicted by transition state theory or other theories of bimolecular rate coefficients. A qualitative test of various potential energy surfaces can also be made using such data. Using the theory of Bigeleisen and Wolfsberg of kinetic isotopic effects and several methods of constructing potential energy surfaces (Wheeler et al, Sato, Johnston and Parr ) Timmons and Weston ° found no surface which predicted rates to within better than 40 % of the measured values taken as a whole. 

Johnstone scrubber coefficient, A = 0.14 Inertial impaction parameter, ij/ = 105... 

Unlike the Johnstone equation approach, this method requires specifying two coefficients. The validity and accuracy of the coefficients available from the literature for the contact power theory equations have been questioned. Some numerical values of a and fi for specific particulates and scrubber devices are provided below. 

Correlation of Bravo, Rocha, and Fair for Structured Packings Bravo et al. (1985, 1992) developed correlations for the prediction of mass transfer coefficients for structured packing with the geometry shown in Figure 12.9. Bravo et al. (1985) use the correlation of Johnstone and Pigford (1942) to estimate the Sherwood (Shj/) number for the vapor phase... 

Perkins and Johnston (1963) presented the following correlation for the longitudinal dispersion coefficient,... 

FIGURE 2.3 A plot of longitudinal dispersion coefficients for unconsolidated, random packs of uniform-size sand or beads. Source Perkins and Johnston (1963). 

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