Contact experiments results

So that the results from the delayed-contact and variable-contact data could be compared, they were normalized to give equal signal intensities at a contact time of 0.5 ms (zero delay in the delayed-contact experiment) after the variable-contact data had been adjusted to allow for the fact that full equilibration of proton and polarisation had not quite been reached after 0.5 ms. The difference in normalised signal intensity between the variable-contact and delayed-contact experiments, at a given time point t, is then a measure of the amount of 13C cross-polarising between 0.5 ms and t. 

It is important to stress that ATR absorbance is strongly affected by the sample/crystal contact. Quantitative results are thus difficult to obtain even if the contact is maintained during the sample rotation that is required to record all four polarized spectra. A reference band that does not show significant dichroism is thus most often used to normalize the polarized absorbances in order to obtain quantitative data. For instance, the 1,410 cm-1 band of PET has often been chosen for that purpose, not only for ATR studies but also for specular reflectance (see below) and even transmission studies when the sample thickness is not uniform. It was shown that an appropriate normalization is possible even if no such reference band is available, by using a combination of two bands with orthogonal dichroism [34]. When performing ATR experiments, one should also make certain that the applied pressure does not create artifacts by affecting the structure of the sample. 

REPEAT CONTACT EXPERIMENTS AT CONSTANT REACTION PARAMETERS RESULTS AND TRENDS... 

An example of the data, broken down into the 13 product groups, calculated tom the distillation and GC analysis of the hydrocracked liquids from CoMo-catalysed experiments is shown in Table II. It can be seen that the distribution of each of the contacts is similar, reflecting no dependence on repeat contact, even in the case of the first contaa which used tosh catalyst. This situation was generally observed for the other catalysts used and a summary of the r ts for the four catalysts is shown in Table III. The results for ZnW could be interpreted as a gradual decrease in conversion to material bpt <260 C or <275°C. However, this interpretation would depend highly on the reliability of the result for the fifth contact, the two runs of which were carried out on the same autoclave rather than one on each autoclave. The discussion further in the text does indicate that, at shorter contact times, conversions can be dependent upon the autoclave used, and the low value for this fifth contact probably results tom this dependence rather than a dependence on contact Hence it was concluded that, for all the catalysts, conversions to the various bpt materials were independent of repeat contact. 

Sulphur analysis of the liquids and analyses of the used catalysts revealed the same type of trends as are expounded fortiie experiments at 400 C. Therefore, for all of the repeat contact experiments, irrespective of catalyst or experimental condition, constant catalyst activity was achieved after a single contact so that results from single contacts in autoclaves of the design used in this investigation would be representative of steady state liquefaction conditions, enabling the autoclaves to be used for the rapid accumulation of liquefaction data. 

As in Sect. 2, another experiment is required to evaluate all the diffusivities, i.e., to obtain the correct value for Deiam for use with Table 2. Bai and Miller [4] repeated the contacting experiment of Fig. 13 except that only a thin layer of AOT was present initially. As a result, the similarity solution, which assumes a semi-infinite AOT phase, is not valid after a short transient. Instead the governing equations must be solved numerically with the boundary... 

Figures 10, 11 and 12 show the results of the contact experiments for the basalt, shale and quartz monzonite samples. The rate of adsorption was rapid during the first two weeks and changed slowly thereafter. In these experiments Pu, Am and Cm exhibited behavior similar to the results obtained in the blank experiments. Uranium showed moderate adsorption ( 50 percent) on the basalt but only slight adsorption (10-20 percent) on the shale and quartz monzonite wafers. Neptunium showed strong adsorption (70-80 percent) on the shale and slight adsorption ( v 10 percent) on the basalt and quartz monzonite.

The values obtained for n-hexanol-water were = 24.6 and = 1.9 dynes/cm and for water-hexanol, = 22 and yf = 12.4 dynes/cm. As regards the contact angle results obtained with n-hexanol, values of Oow obtained from Equations 14 and 15 and by experiment show a wide disparity. See Tables IV-VII. For paraffin wax, both equations predict zero contact angle for n-hexanol whereas the experimental values are 45° 6a) and 37°C Or), As discussed earlier, adsorption of alcohols at the solid/liquid interface may affect the wetting behavior of substrates. These effects are not accounted for by the Fowkes or Wu treatment, and hence it is not unexpected that these equations do not correlate with experimental Oow values for hexanol/water. 

Diffusion studies were made using an Isopar M/Heavy Aromatic Naptha (IM/HAN) 9 1 oil mixture (Exxon). Isopar M and HAN are refined paraffinic and aromatic oils, respectively. Figure 3 shows equilibrium salinity scans measured in the laboratory for equal-volume mixtures of the surfactant solution and oil. Since room temperature varied somewhat, the effect of temperature on phase behavior was determined. As Figure 3 shows, there is a small temperature effect, especially at the lower salinities. However, it is not large enough to have influenced the basic results of the contacting experiments. Optimum salinity, where equal volumes of oil and brine are contained in the middle phase, is approximately 1.4 gm/dl. 

At approximately optimum salinity, spontaneous emulsification of brine drops in the oil phase began in both systems. This phenomenon resulted from local supersaturation of the oil phase, as explained in the discussion section below. The amount of emulsification tended to increase with increasing salinity. As a result, the cloud of emulsion drops began to obscure the interface between the microemulsion and oil, making interface position measurements difficult. These observations of spontaneous emulsification confirm the results of the earlier contacting experiments performed in the horizontal configuration ( 4). 

At approximately S = 0.2 (this value is somewhat dependent on other phase behavior parameters), passage of the calculated diffusion path through the brine phase becomes possible. This change corresponds closely to the point at which brine began forming by diffusion in the contacting experiments and, as a result, indicates that formation of two intermediate phases is preferred over the formation of a single microemulsion phase. A... 

Although the contacting experiments were performed with surfactant systems typical of those used in enhanced oil recovery, application of the results to detergency processes may be possible. For example, the growth of oil-rich intermediate phases is sometimes a means for removing oily soils from fabrics. Diffusion path theory predicts that oil is consumed fastest in the oil-soluble end of the three-phase regime where an oil-rich intermediate microemulsion phase forms. 

To determine the macro-friction properties, the tangential or friction force was measured by a tribometer, and the contact area evolution was recorded by video camera. Friction stress was calculated by dividing each force value by the corresponding contact area. Results of the macro-friction experiments are presented in Table 5.2. 

Great care must be taken when using this instrument, as each of the measuring anvils has a spherical end, resulting in point contact. Experience in use is essential to develop a feel , and the instrument must be moved slightly back and forth and up and down to ensure that the measurement is taken across the widest point. 

The results of such contact experiments are highly dependent on the presence of moisture and on the addition of ionic salts to the polymers. Especially interesting are those studies with polymers blended with ionomers. In a model of... 

It can be expected that computer simulations of dynamically loaded concentrated contacts will soon be able to predict the behaviour more accurately. Thus, there is a need for an independent verification by detailed experimental results. Theoretical models yield film thickness, pressure, and temperature distributions in space as a function of time. Experiments result in distributions in time as a function of position in space. Experiment and theory can only be compared if the data are converted into the same way of representation. Therefore, uny experiments with a high resolution are needed. The film thickness plays a critical role from a designer s point of view. However, the literature is rather scarce on this point, as can be concluded from the following brief survey. 

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