Unevenness

Wastage does not have to be dramatic to be easily observed on a full coverage scan. Figure 14 and 15 show a tube with 0,2 ram of eccentricity that has been in service for two years and has 0,15 mm of wastage near the drum. New tubes are good indicators to determine wastage rates as the scans are very clean without noise of uneven rough corrosion. 

Barnes and co-workers have studied mixed-monolayer systems [278,281,283,284] and found some striking nonidealities. Mixed films of octadecanol and cholesterol, for example, show little evaporation resistance if only 10% cholesterol is present [278] apparently due to an uneven granular microstructure in films with cholesterol [284]. Another study of cellulose decanoate films showed no correlation between holes in the monolayer and permeation rate [285]. Polymerized surfactants make relatively poor water evaporation retarders when compared to octadecanol [286]. There are problems in obtaining reproducible values for r [287] due to impurities in the monolayer material or in the spreading solvent. 

Nonetheless, when counting all stmctures solved over time, one finds a strong predominance of studies in certain narrow categories, as exlhbited by the following uneven statistics ... 

The value of the additional degree of freedom s can change and so the time step in real tin can fluctuate. Thus regular time intervals in the extended system correspond to a trajecto of the real system which is unevenly space in time. 

Fig. 8.5 To achieve a uniform distribution of points over the surface of a sphere it is necessary to sample from cos 8 rather than 6. If the sampling is uniform in 8 then the number of points per unit area increases with 6, leading to an uneven distribution over the sphere.

These dyes possess two independent chromophoric chains of even methine (neutro) and uneven methine (cyanine) fixed on a central ketometbylene nucleus. The methylene reactive group is first used for the neutrocyanine synthesis in position 5. the, quaternization of which can ensure a subsequent polymethine synthesis in position 2 of a cationic dye by ordinary means (Scheme 58). As indicated, this quaternized neutrocyanine (37) may as well give another neutrocyanine. 

In using the table for pore size calculations, it is necessary to read off the values of the uptake from the experimental isotherm for the values of p/p° corresponding to the different r values given in the table. Unfortunately, these values of relative pressure do not correspond to division marks on the scale of abscissae, so that care is needed if inaccuracy is to be avoided. This difficulty can be circumvented by basing the standard table on even intervals of relative pressure rather than of r but this then leads to uneven spacings of r . Table 3.6 illustrates the application of the standard table to a specific example—the desorption branch of the silica isotherm already referred to. The resultant distribution curve appears as Curve C in Fig. 3.18. 

Plywood is a panel made from wood veneers (thin shces or sheets) bonded to one another. Generahy each ply is oriented at right angles to the adjacent ply, and the two face pHes should have the grain direction parahel to each other. Thus most plywood wih have an uneven number of pHes, such as 3, 5, 7, or more. An exception to this is a four-ply constmction in which the two core pHes are oriented parahel to one another and perpendicular to the two face phes. 

Despite their theoreticaUy poor washing performance, due to uneven wash distribution and excessive mn-off because the filter surface is not horizontal, many multicompartment dmm filters continue to be used as cake washing filters. Effective washing of the filter cloth can be done only with the belt discharge type, where the cloth leaves the dmm for a brief period and can thus be washed on both sides. 

Some attempts have been made to reslurry the filter cake without having to open the filter press. However, a number of problems appear, eg, bending of the plates due to uneven cake deposition or cavitation, uneven dewatering and washing within the frames, and plugging of the inlet ports. 

Retention aid polymers are used in a very high shear environment, so floe strength and the abiHty for floes to reform after being sheared (43) is important. The optimum floe size is a compromise. Larger floes give better free drainage, but tend to produce an uneven sheet due to air breakthrough in... 

Naphtha desulfurization is conducted in the vapor phase as described for natural gas. Raw naphtha is preheated and vaporized in a separate furnace. If the sulfur content of the naphtha is very high, after Co—Mo hydrotreating, the naphtha is condensed, H2S is stripped out, and the residual H2S is adsorbed on ZnO. The primary reformer operates at conditions similar to those used with natural gas feed. The nickel catalyst, however, requires a promoter such as potassium in order to avoid carbon deposition at the practical levels of steam-to-carbon ratios of 3.5—5.0. Deposition of carbon from hydrocarbons cracking on the particles of the catalyst reduces the activity of the catalyst for the reforming and results in local uneven heating of the reformer tubes because the firing heat is not removed by the reforming reaction. 

Feed systems utilizing gravity are rarely used. Line pressure is usuaHy adequate for smaH systems. AuxHiary pumps are required in larger systems to assure proper flow through aH units and to avoid uneven flow should line pressure decrease as other demands for water or the process stream occur elsewhere in the facHity. 

Finishing and Fabrication. Since laminates are normally pressure cured in flat-bed presses and pHes overextend the plates, laminates have rough or uneven edges when removed from the press. These edges are sawed off and the back of the laminate is often sanded to improve the strength of subsequent bonding to various substrates. 

Construction. In the constmction phase there are two ways problems can arise. The more common of these is poor workmanship. Uneven foundation settlement and faulty constmction, eg, use of the wrong materials or insufficient quantity of rebars, are but two examples. Only qualified builders, close inspection during constmction, and enforcement of a tightly written specification are necessary factors. 

After exiting the economizer, the feedwater is directed iato the boilet s cylindrical steam dmm via a common header pipe that penetrates the dmm s wall and distributes the water evenly within the dmm through holes drilled ia the upper side of the distribution pipe. Because the distribution pipe is located axially below the waterline ia the lower section of the steam dmm, the incoming feedwater mixes thoroughly with the water ia the dmm and prevents any significantly uneven temperature distributions within the dmm. 

Inlet Piping Configurations. An incorrect piping configuration can create undesirable flow distortions that, especiaUy for double-suction pumps, means turbulence. Air pockets trapped in the pipe can cause uneven flow, vibrations, and pump damage. 

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