Shape index test

The test is conducted on each aggregate fraction d/Dj, where D (maximum particle size) 2d (minimum particle size). 

More information about conducting the test and the minimum quantities of aggregate required for the test is given in CEN EN 933-4 (2008). 

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This test proposed by the American standard ASTM D 4791 (2010) is equivalent to the Flakiness and Shape Index test methods proposed by the European standards. It determines the percentage of flat particles, elongated particles or flat and elongated particles in coarse aggregates (retained on 9.5 mm or 4.75 mm sieve depending on the requirements). 

Part 2 Determination of particle size — Test sieves, nominal size of apertures Part 3 Determination of particle shape of aggregates — Flakiness index Part 4 Determination of particle shape of aggregates — Shape index... 

CEN EN 933-4. 2008. Tests for geometrical properties of aggregates - Part 4 Determination of particle shape-Shape index. Brussels CEN. 

A simple preliminary test of the JMAYK applicability to each studied case is worth of mentioning. The simple multiple of temperature, T, and the maximum reaction rate, da/dt, which should be confined to the value of 0.63 0.02, can be used to check its appropriateness. Another handy test is the value of shape index, i.e., the ratio of intersections, b and bz, of the in inflection slopes of the observed peak with the linearly interpolated peak baseline, which should show a linear relationship of the kind = 0.52 + 0.916 Tu/Ts - , where Ti s are the respective inflection-point temperatures [397,530]. 

There are a number of index tests in which the flow is driven by drag. Most are based on rotating a disk or other complex shape in a large quantity of the sample. These geometries are used because they are easy to load or because they help sample mixing. 

Objects other than balls or cones are used as index tests for GTXs. The pyramid drop test is similar to the cone drop test but with a different shape. The pyramid should represent the angularity of a stone but the test is not used in this industry. 

When other fillers such as barium sulfate, calcium carbonate and glass fiber were incorporated into flame-retardant PP systems, similar results were obtained, i.e. addition of fillers led to poor flame-retardancy in UL94 and oxygen index tests. The degree of decrease in flame-retardanry was dependent on the types of fillers incorporated, which might be due to filler size, shape, and chemical properties of the fillers. 

R.M. (1981) Introduction of constraint index as a diagnostic test for shape selectivity using cracking rate constants for n-hexane and 3-methylpentane. 

It has been shown that the retention behaviour of benzene, butanol, pentan-2-one, nitropropane, and pyridine can be used to classify stationary phases in terms of their polarity (W.O.McReynolds, J. chromatogr. Set., 1970,5,685-691). The retention indices of each of these five reference compounds are measured, first on the stationary phase being tested and then on a standard phase (squalane). The differences in retention index between the two phases (AI) for the five reference compounds are added together to give a constant which is a measure of the polarity of the stationary phase. This constant is known as iheMcReynolds Constant and can be used to compare the ability of stationary phases to separate different classes of compounds (see below). However, this constant gives no information about peak shape, temperature limits, or the suitability for use in capillary colimms. 

The main requirement for exact and reproducible results is that the sample undergoes laminar flow during testing. Laminar flow appears as streamlined with a velocity profile of parabolic shape when monitored in a tube viscometer. For a Newtonian sample, shear stress and shear strain rate are at a maximum in close proximity to the walls of the test tube, and zero in the center. Shear thinning samples show truncated flow patterns, and the tendency to plug flow increases with a decrease in the power law index. In rotational viscometers laminar flow is the movement of the sample in concentric circles around the axis of rotation of the instrument. 

It is not easy to compare the activity of the V-W-Ti catalysts here tested with the lot of chromia, Pt and Pd based catalysts previously used because they have different shapes (monoliths and spheres) and because very different particle sizes arc involved (having thus very different effectiveness factors). For conqiarison purposes, all X-T curves were adjusted to a simple fust order kinetic model (with rate based on overall volume of catalyst, both for monoliths and for fixed beds). From the kinetic constants so obtained (see details of the method in ref 7), the preexponential factors (ko) of the Arrhenius law and the apparent energies of activation (E, p) were calculated for all catalysts. One example is shown in Figure 17. By the well Imown compensation effect between ko and E,pp, the kg values so obtained were recalculated for a given E.pp value of 44 kJ/mol. Such new ko value was used [7] as an activity index of the catalyst. 

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