Development outward

KADLECEK With respect to conifers, when the leaf starts to fold back from an emerging fascicle or at least a pack of needles, it seems to me you ve got the pocket you need to hold the water. Since that s also the growing tissue, would that not seem to be a fairly sensitive area and explain the sometimes- seen necrotic bands that seem to develop outwardly with time ... 

In the case of alloys having one constituent considerably more reactive to oxygen than the others, conditions of temperature, pressure and atmosphere may be selected in which the reactive element is preferentially oxidised. Price and Thomas used this technique to develop films of the oxides of beryllium, aluminium, etc. on silver-base alloys, and thereby to confer improved tarnish resistance on these alloys. If conditions are so selected that the inward diffusion of oxygen is faster than outward diffusion of the reactive element, the oxide will be formed as small dispersed particles beneath the surface of the alloy. The phenomenon is known as internal oxidation and is of quite common occurrence, usually in association with a continuous surface layer of oxides of the major constituents of the alloy. 

Figure 8.22-d, on the other hand, gives an example in which the link dynamics lags behind the value development. In this example, the boundary proceeds outward... 

Fluids whose behaviour can be approximated by the power-law or Bingham-plastic equation are essentially special cases, and frequently the rheology may be very much more complex so that it may not be possible to fit simple algebraic equations to the flow curves. It is therefore desirable to adopt a more general approach for time-independent fluids in fully-developed flow which is now introduced. For a more detailed treatment and for examples of its application, reference should be made to more specialist sources/14-17) If the shear stress is a function of the shear rate, it is possible to invert the relation to give the shear rate, y = —dux/ds, as a function of the shear stress, where the negative sign is included here because velocity decreases from the pipe centre outwards. 

Fr is the radial die wall force that develops because the powder is in a confined environment (i.e., not able to spread outward as pressure is applied down upon it because it is residing within the die). The coefficient of friction at the die wall, iw, is due to the shearing adhesion that occurs along the die a as the powder is made more dense and compressed. The following relationship between and FD, iw, and Fr is found to exist ... 

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