Obscuration effectiveness

This emissive power is assumed to be over the whole flame surface area, and is significantly less than the emissive powers that can be calculated from point source measurements. Increasing the pool diameter reduces the emissive power due to the increasing black smoke outside the flame and the resulting obscuration effect on the luminous flame. 

The measurement of screening performance of smokes is important because smoke screens are one of the countermeasures for IR surveillance systems. The performance of smoke formulations is decided in terms of total obscuring power (TOP), yield factor (Y), mass extinction coefficient (a) followed by calculation of obscuration effectiveness (a. Y. p). These parameters are defined in the following manner. 

The analysis of smoke and soot formation from polymers during combustion has been extensively studied 50,51 however, less is understood on how hydrated fillers influence this mechanism. It is likely that smoke reduction results from the deposition of carbon onto the high surface area oxide surface, produced on the decomposition of the filler.38 The volatilization of carbonaceous residue as carbon oxides then occurs, reducing obscuration effects from the smoke. 

This relatively rapid type of activation explains the autocatalytic curves obtained when initial rates of citrulline synthesis are compared with those obtained after several minutes incubation. Table IV demonstrates that by increasing the acetyl glutamate concentration and the length of incubation for the over-all synthesis, the activation was obscured. This is why the activation effect remained undetected until extremely short incubation times and low temperatures were used. Bringing a complicated reaction mixture to incubation temperature, waiting for equilibration, and completing with a last component, as is often done, may obscure effects such as the ones described here. 

Dipole-dipole interactions play an important role in conformational analysis so it might be expected that a direct effect on barriers to inversion could be demonstrated. We shall show below that much is known about the inversion of heterocyclic six-membered rings, but as was discussed in Section II, when one or more heteroatoms replace carbon atoms in the cyclohexane skeleton large changes in other interactions take place, and may obscure effects due to dipole-dipole interactions. There are some comparisons nonetheless which seem to illustrate the effect of such dipole interactions. 

Vapor Density —Regardless of whether the chemical agent is a gas or a smoke, it must ha e a vapor density greater than that of air for other-Mise, as soon as the agent is released from its container, it w ill immediatel v rise from the surface of the ground and thus lose its physiological or obscuring effect. 

The surface emitted power or radiated heat flux may be computed from the Stefan-Boltzmann equation. This is very sensitive to the assvuned flame temperature, as radiation varies with temperature to the fourth power (Perry and Green, 1984). Further, the obscuring effect of smoke substantially reduces the total emitted radiation integrated over the whole flame surface. 

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