Propagation velocity, mechanical

The flux-corrected-transport technique was also used by Phillips (1980), who successfully simulated the process of propagation of a detonation wave by a very simple mechanism. The reactive mixture was modeled to release its complete heat of combustion instantaneously after some prescribed temperature was attained by compression. A spherical detonation wave, simulated in this way, showed a correct propagation velocity and Taylor wave shape. 

To understand the mechanism of flame quenching in narrow channels in detail, one should first examine the data of flames in mixtures of constant composition, but in charmels of different sizes (Figure 6.1.2). The measured propagation velocities in stoichiometric propane/ air mixture are shown in Figure 6.1.2a. For channel widths slightly larger than the quenching distance, the... 

Detailed experimental studies on these gas-solid combustion reactions reveal the dependence of combustion and propagation characteristics, like front propagation velocity, combustion temperature and degree of conversion, on operating parameters like nitrogen pressure, particle size and morphology of the reactant metal and dilution of the gas and solid phases. From these studies the optimum synthesis conditions for a variety of nitrides are determined and information about the mechanisms of several gas-solid combustion reactions is obtained. With the aid of combustion theory, the apparent values of activation energy for several nitridation reactions are calculated from measured combustion characteristics. 

We may imagine that a flat piston is located at the coordinate origin. At the initial time it begins to move into the gas so that ir(l) is the gas pressure at the piston s surface. Then, after a time of order r, the piston is removed or begins to move left from the gas with a velocity exceeding the propagation velocity of the gas compressed by it. Another possible mechanism for generating this motion is the explosion of a thin, flat layer of explosive which lies on the surface of the cold gas. 

The mechanism of the reaction of hydrogen with bromide is known today in complete detail all the individual stages of the reaction, their probabilities, and activation heats are known. Because of this, it was possible to calculate the flame propagation velocity from kinetic data after the combustion temperature had been found by thermochemical computations, and with... 

We shall show that both mechanisms identically lead to relative thermal losses which are inversely proportional to the square of the propagation velocity. 

In mechanism b, under given conditions of heat transfer, each elementary quantity of combustion products is cooled at a certain rale. For a given time derivative of the temperature, the derivative with respect to the coordinate is inversely proportional to the propagation velocity, and the same is true of the heat flux in the direction of the flame which carries heat out of the... 

An important qualitative conclusion is that by increasing the diameter the heat transfer by conduction may be made arbitrarily small. In the absence of another mechanism of heat transfer, by increasing the diameter we may arbitrarily decrease the flame propagation velocity at the limit. 

The first three mechanisms of surfactant adsorption have been criticized mainly because crack propagation velocities in comminution devices are often much more than the rate of adsorption of the surfactants normally used as grinding aids (20). There is considerable evidence and concurrence of opinion on the prevention of agglomeration as the mechanism of grinding aid action (21). 

Using the experimental values for the width of the traveling wave front (portion be, Fig. 8), let us estimate the propagation velocity for the case of a thermal mechanism based on the Arrhenius law of heat evolution from the known relationship U = a/d, where a 10"2 cm2/s is the thermal conductivity determined by the conventional technique. We obtain 5 x 10"2 and 3 x 10-2cm/s for 77 and 4.2 K, respectively, which are below the experimental values by about 1.5-2 orders of magnitude. This result is further definite evidence for the nonthermal nature of the propagation mechanism of a low-temperature reaction initiated by brittle fracture of the irradiated reactant sample. 

The autowave chemical conversion in a film was initiated by a local mechanical disturbance in the form of a puncture or scratch. Figure 14 presents the results of measuring the averaged value of the wave-front propagation velocity as a function of the irradiation dose. It is seen that for... 

Changes in SAW propagation velocity and attenuation are determined by the mechanical impedances at the substrate/film interface resulting from film translational and strain modes. The impedance associated with each film translation is jtaph, and with each strain mode is where Ef i are taken from Table... 

The ability to use SAW devices for real-time monitoring of corrosion of thin metal films in gaseous environments has been demonstrated. Metal films, ranging in thickness from a few Angstroms to a micron, were deposited on the prop-agatimi path between transducers. Since the acoustic-wave propagation velocity depends upon the mass and mechanical properties of the film, any change in these properties due to corrosion alters the velocity. 

It should be mentioned, that elastic energy is only radiated by events whose propagation velocity is in the order of the shear velocity (which is scale-independent). Slow processes like creep events do not emit energy to an extent which is worth mentioning. Such events are aseismic. It should be further noted, that in acoustic emission other than double-couple mechanisms like tensile mechanisms play a more prominent role than in earthquake theory. 

Principle of circularity. The principle of circularity, applied to the loop of paths in this Formal Graph, immediately provides a general wave equation, which has therefore the same shape whatever the energy variety. (The classical wave equation is found at the condition of being within the restricted framework of the linearity of system properties.) The link between the property of space time and the system properties stems from this circularity. In this systan, this link is created by the relationship between the propagation velocity (velocity of phase) and the ratio of the mechanical tension on the lineic mass. 

Two different velocities. The space-time velocity o is a vector that should not be confused with the velocity v of an object in translational mechanics, which is a state variable contrary to the phase or propagation velocity u. The latter is a purely space-time property having no energetic content. 

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