Dilated particulate

A particulate mass may offer a significant resistance to both shear and tensile forces, and this is specially marked when there is a significant amount of agglomeration. Even in non-agglomerating powders there is some resistance to relative movement between the particles and it is always necessary for the bed to dilate, that is for the particles to move apart, to some extent before internal movement can take place. The greater the density of packing, the higher will be this resistance to shear and tension. 

Physical Effects of Filler. Dispersion of any hard particulate matter in a soft matrix will yield a composite with quite different properties. The two main causes for these effects are load sharing of the filler particles and strain dilatation of filled elastomers. 

The bulk density of particulate solids increases by compaction. Dilation, mentioned earlier, occurs only in the presence of a free surface, which allows for a loosening of the packing arrangements of the particles. The increase in density, or decrease in porosity, seems to follow an exponential relationship with the applied pressure (38,39)... 

An impact modifier is a rubber phase dispersed in particulate form throughout the matrix of a polymer solid. Unlike plasticizers, the rubber particles retain their intrinsic properties as a separate phase. The glass transition temperature of the parent matrix is not lowered by the addition of an impact modifier. The rubber particles do two things to the parent matrix phase (2,3,4) they act as stress concentrators (i.e., a large strain will start in the matrix near the interface) and they enhance the multi-axiality in stress. As multiaxial tensile strength near the interface further enhances dilatation, which shortens the mechanical relaxation time, the otherwise brittle polymer solid of the matrix will undergo plastic deformation in the vicinities of the rubber particles. 

Experience has shown structured fluids to be more difficult to manufacture, due to the complexity of their rheological profiles. In addition to elasticity, dilatancy, and rheopexy, certain structured fluid compositions may exhibit solid-like properties in the quiescent state and other flow anomalies under specific flow conditions. For emulsions and solid particulate dispersions, near the maximum packing volume fraction of the dispersed phase, for example, yield stresses may be excessive, severely limiting or prohibiting flow under gravity, demanding special consideration in nearly all unit operations. Such fluids pose problems in... 

Likely, the intact dense sands involved (porosities 25-32%), though cohesionless, cannot liquefy or erode from an intact face because of strong dilation and arching. Sanding is viewed as a liquid-solid coupling process that takes the geological material progressively from an intact dense state to a dilute particulate suspension. 

An irritant can be a gas, liquid, or fine particulate matter. Ammonia is a familiar and common irritant. Irritants injure the body by inflaming the tissues at the point of contact. Heat, redness, swelling, and pain are signs of inflammation. Mild irritants cause the capillaries to dilate and fill with blood, causing the redness and increased heat. The permeability of the capillary walls change, and fluid passes from the blood into the spaces between the tissues and causes swelling and pain. Strong irritants can produce blisters. 

The phosphodiesterase which cleaves cyclic AMP to adenylate is found in both particulate and soluble fractions of tissue homogenates, and it is inhibited by pyrophosphate and ATP, as well as by caffeine, theophylline, and theobromine. These three methylated xanthines cause central nervous system and respiratory stimulation, smooth muscle relaxation, diuresis, coronary dilatation, cardiac stimulation, and skeletal muscle stimulation these effects are believed to be due to increased tissue concentrations of cyclic AMP resulting from inhibition of phosphodiesterase activity. 

Will the flow route include regions of dilation, with freedom for inter-particulate activity ... 

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