Recessive

Note that for certain older engines, small quantities lead deposits from combustion could have a positive effect as a solid lubricant and prevent exhaust valve recession. For these motors which still represented in 1993 from 20 to 30% of the French automotive fleet, the use of unleaded fuel is not possible. 

To obtain the necessary pressure on the lid, and for general protection when the bomb is being heated, the bomb is placed in a hea y metal case G, in which the collar E of the bomb rests in a circular recess at the top of G, and the base of A just appears through the bottom of G. The lid H of the case screws down over G, and has an orifice through which the pillar F of the bomb projects when H is screwed firmly down onto G. The bottom portion of G and the sides of H are made of hexagonal cross-section so that both can be firmly held with suitable tools whilst H is being screwed down and is thus thrusting the lid C of the bomb firmly down onto the base A. 

Fig. 2. A simplified material thermal performance analysis for a reentry vehicle thermal protection system where = density x surface recession thickness = total aerodynamic heat/heat of ablation ...

The United States was a net exporter in the 1980s except for 1984—1986 when it was a net importer. This reversal resulted from a number of conditions including the global recession, foreign relationships, new overseas capacity especially in Japan and South Africa (which in 1988 was the largest exporter to the United States), and the increase in other countries of the ratio of phenol production to acetone demand (45). 

Production of pentaerythritol in the United States has been erratic. Demand decreased in 1975 because of an economic recession and grew only moderately to 1980 (69). The range of uses for pentaerythritol has grown rapidly in lubricants (qv), fire-retardant compositions, adhesives, and other formulations where the cross-linking capabiUties are of critical importance. 

Both flush plates and recessed plates can be specified. Recessed plates obviate the need for the frames but are tougher on filter cloths due to the strain around the edges. These presses are more suitable for automation because of the difficulty of the automatic removal of residual cake from the frames in a plate-and-frame press. Recessed plates with no frames limit the chamber width to less than 32 mm to limit the strain on the cloth, whereas plate-and-frame presses allow this to be more than 40 mm if necessary. 

The vertical recessed plate automatic press is shown schematically in Figure 15. Unlike the conventional filter press with plates hanging down and linked in a horizontal direction, this filter press has the plates in a horizontal plane placed one upon another. This design offers semicontinuous operation, saving in floor space, and easy cleaning of the cloth, but it allows only the lower face of each chamber to be used for filtration. 

Fig. 21. Membrane plate press, ie, recessed plate with variable chamber press.

Another advantage of the membrane plate is its flexibiUty to cake thickness, ie, thinner cakes can be easily handled without loss of dryness. Cake release characteristics are also improved by deflation of the membrane prior to cake discharge. Alternating arrangements, in which the membrane plates and the normal recessed plates alternate, have been used to reduce cost. 

The vertical recessed plate automatic press, shown schematically in Figure 15 and described previously, is another example of a horizontal belt pressure filter. Cycle times ate short, typically between 10 and 30 minutes, and the operation is fully automated. The maximum cake thickness is about 35 mm washing and dewatering (by air displacement) of cakes is possible. Apphcations include treatment of mineral slurries, sugar, sewage sludge, and fillers like talc, clay, and whiting. 

Fig. 11. Stages of disjoining film behavior in flotation upon particle—bubble coUision (a,b) film thinning (c) film mpture and (d) film recession and...

Commercial production and consumption of glycerol has generaHy been considered a fair barometer of industrial activity, as it enters into such a large number of industrial processes. It generaHy tends to rise in periods of prosperity and faH in recession times. 

In Europe total consumption of plastic foam insulation for 1992 was 29 x 10 m (>12 billion board ft) withHttle or no growth seen from 1991. AU products were expected to grow by an average of 1% due primarily to the continued effects of the economic recession. 

Shaping. Most metal-shaping operations in ECM utilize the same inherent feature of the process whereby one electrode, generally the cathode tool, is driven toward the other at a constant rate when a fixed voltage is appHed between them. Under these conditions, the gap width between the tool and the workpiece becomes constant. The rate of forward movement between the tool and the workpiece becomes constant. The rate of forward movement of the tool is matched by the rate of recession of the workpiece surface resulting from electrochemical dissolution. 

In the United States, fibers and injection mol ding are the main appHcations for polypropylene (Table 8), followed by film. In Europe and Japan, injection mol ding appHcations predominate (Table 10). This market area is more likely to decline in economic recession, as consumers postpone purchases of apphances and automobiles. Film appHcations are important in both regions, but fibers are a much less important use for polypropylene in Japan than in other developed regions. The heavy use of polypropylene nonwovens in the manufacture of disposable diapers and similar products, and the wide use of polypropylene carpets in the United States, account for the greater consumption of fibers. 

The principal worldwide manufacturers of nylon resins are given in Table 6. Total sales of nylon plastics in the United States and Canada in 1993 were 331,000 metric tons (37). West European sales were 352,000 t and Japanese sales 220,000 t (37). Figure 7 shows how sales in the United States have steadily increased since 1967 (38) and also how the price of nylon-6,6 has changed (39). The effect of the oil price rises, the boom of the mid-1980s, as well as the oil price reduction and the recession that followed are clearly evident. Table 7 shows the variation of price across different polyamide types. 

Market prices are extremely volatile and follow cycles of advance and decline related to fluctuations ia global iaventories and world economic forces. For example, for northern bleached softwood kraft, which is considered a global benchmark pulp grade, market price went from 840/t ia 1990 down to 440/t ia 1993 as a result of oversupply and worldwide recession (3). By 1995 virtually all of the price losses had been recovered. 

Frame-Mounted. For medium and severe appHcations, when nozzle loads and thermal transients tend to impose high stresses and internal deflections inside the pump, frame-mounted designs are used. Typically, these designs use conventional impellers, but recessed impeller designs are also available (Fig. 5). 

Fig. 5. Frame-mounted pump having recessed impeller.

The Magic Carpet system (AstroTurf Industries) (13) is a novel installation technique in which turf and adherent underpad are unwound from a core and floated onto the subbase of a playing field by air pressure suppHed from ducts in the base. To expose the subbase for other sports uses, the turf—pad combination is roUed up and stored at the edge of the field or in a recessed storage compartment. 

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