Flat disc

Aerodynamic Downwash Should the stack exit velocity be too low as compared with the speed of the crosswind, some of the effluent can be pulled downward by the low pressure on the lee side of the stack. This phenomenon, known as stack-tip downwash, can be minimized by keeping the exit velocity greater than the mean wind speed (i.e., typically twice the mean wind speed). Another way to minimize stack-tip downwash is to fit the top of the stack with a flat disc that extends for at least one stack diameter outward from the stack. 

The maintenance of product formation, after loss of direct contact between reactants by the interposition of a layer of product, requires the mobility of at least one component and rates are often controlled by diffusion of one or more reactant across the barrier constituted by the product layer. Reaction rates of such processes are characteristically strongly deceleratory since nucleation is effectively instantaneous and the rate of product formation is determined by bulk diffusion from one interface to another across a product zone of progressively increasing thickness. Rate measurements can be simplified by preparation of the reactant in a controlled geometric shape, such as pressing together flat discs at a common planar surface that then constitutes the initial reaction interface. Control by diffusion in one dimension results in obedience to the... 

A similar connection between the world around us and cosmology can be found in the land between the Tigris and Euphrates. The Earth was regarded as a flat disc, surrounded by a vast hollow space which was in turn surrounded by the Armament of heaven. In the Sumerian creation myth, heaven and Earth formed... 

Figure 6.24 Photographic representation of a range of filter types and their stainless steel housing. Most filters used on an industrial scale are of a pleated cartridge design, which facilitates housing of maximum filter area within a compact space (a). These are generally housed in stainless steel housing units (b). Some process operations, however, still make use of flat (disc) filters, which are housed in a tripod-based stainless steel housing (c). All photographs courtesy of Pall Life Sciences, Ireland...

The Golgi apparatus (63-69) or collection of all the dictyosomes is composed of flat-disc shaped sacs or cistemae. The Golgi apparatus... 

None of the set-ups discussed so far provides stirring of the electrolyte for bubble removal or for enhancement of the reaction rates. A standard set-up developed to study kinetic electrode processes is the rotating disc electrode [11]. The electrode is a small flat disc set in a vertical axle. The hydrodynamic flow pattern at the disc depends on rotation speed and can be calculated. An additional ring electrode set at a different potential provides information about reaction products such as, for example, hydrogen. However, because this set-up is designed to study kinetic processes and is usually equipped with a platinum disc, it becomes inconvenient if silicon samples of different geometries have to be mounted. 

Impinging jet nozzles Flat discs (fluid pressures... 

Figure 16.21. Characteristic rotary atomisers (a) Sharp-edge flat disc (b) Bowl (c) Vaned disc (d) Air-blast...

For solid bodies of hard spheres, flat discs and rigid rods one has df=d =3 for hard spheres df=d2=2 for flat discs dj =di=l for thin rods... 

During measurement, the RDE is immersed in the analyte solution. The insulator extends beyond the edge of the flat disc electrode for a further 5-8 mm or so. This additional distance between the electrode and the edge of the cylinder shaft is needed in order to minimize the effects of eddy currents (see Section 7.5 below). 

Mesogen composed of relatively flat, disc- or sheet-shaped molecules. 

The term mesophase is used in reference to the liquid crystalline phase, and the molecular (sub)structures that give rise to this phase are termed mesogens. Macromolecules with rod-like or a flat, disc-like geometries tend to form such... 

The rotary-platform, double-head or Taber abrader, unlike those mentioned above, was not developed by the rubber industry but was intended for very general use. It is of the form (d) in Figure 11.4 but uses a pair of abrasive wheels. Although the degree of slip cannot be varied, the Taber is in other ways a very versatile apparatus. It uses a simple flat disc as the test piece which could, if necessary, be fabricated from more than one piece. The force on the test piece and the nature of the abradant are very readily varied and tests can be carried out in the presence of liquid or powder lubricants. When using the usual type of abrasive wheel, a refacing procedure is carried out before each material tested. 

Another alternative to the use of cartridges is the Empore C18 extraction disk (44). These flat discs have large cross-sectional areas that provide advantages for online preconcentration and cleanup methods with respect to sorption, capacity, backpressure, and stability after repeated use. 

Columnar liquid crystals consist of flat, disc-shaped molecules aligned in columns. These columns may be arranged in a hexagonal pattern as illustrated in Figure 16.4. 

The adhesion of platelets to the subendothelial matrix via specific adhesive GPs is the initial step in primary hemostasis. Binding of platelets to the matrix results in rapid (Fig, 2) morphological conversion of platelets from flat discs to spiny spheres. 

The above materials are useful in highlighting two further aspects of benzene-based chemistry, i.e., (i) transition from 2D to 3D structures and (ii) transition from macromolecular to supramolecular architectures. While already traditional benzene chemistry has proceeded from flat disc-type structures to double and multilayered cyclophanes such as 1831 and 19,32 graphite and its intercalation cannot be understood without considering layer formation. A closely related... 

Fig. 5.1 Cross-sections of disc specimens for measurement of electric strength (a) standard flat disc (b) recessed disc.

The basic flat disc with rim construction has been modified by various manufacturers. Certain benefits are claimed for each design. 

Four flat, disc-shaped laminar flow flames were probed and analyzed using standard microprobing techniques. The flames were composed primarily of CO, H2, 02> and Ar with small amounts of CH4 or natural gas added to simulate intermediate Btu gas mixtures. Gas compositions used in the probings are presented in Table 1. Flames A and B contained excess air, air/fuel equivalence ratio = 1.13 Flames C and D were slightly fuel rich, air/fuel equivalence ratio = 0.93. Each of the mixtures had a CO/H2/X (X = methane or natural gas) mole ratio of 1/1/0.22. 

The simplest kind of a fixed catalyst bed is a random packing of catalyst particles in a tube. Different particle shapes are in use like spheres, cylinders, rings, flat disc pellets or crushed material of a certain sieve fraction. Mean particle diameters range from 2 to 10 mm, the minimum diameter is limited primarily by pressure drop considerations, the maximum diameter by the specific outer surface area for mass and heat transfer. 

Adsorption Studies. Sacks. GB or PVPyr surfaces were made into flat sacks, sealed on three sides by a heat sealing polyester film coated with a polyolefinic adhesive (Seal-Lamin, Seal Inc., Shelton, Conn.). The fourth side was similarly sealed after introducing the solution containing heparin leaving an air bubble enclosed. Such flat sacks, with two coated faces each 12 X 12 cm. (288 cm.2 for adsorption) and over all dimensions of 14 X 14 cm. were held between flat discs at a spacing such that the... 

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