Propagation factors influencing

Intermetallic compound formation may be observed as the result from the diffusion across an interface between the two solids. The transient formation of a liquid phase may aid the synthesis and densification processes. A further aid to the reaction speed and completeness may come from the non-negligible volatility of the component(s). An important factor influencing the feasibility of the reactions between mixed powders is represented by the heat of formation of the desired alloy the reaction will be easier if it is more exothermic. Heat must generally be supplied to start the reaction but then an exothermic reaction can become self-sustaining. Such reactions are also known as combustion synthesis, reactive synthesis, self-propagating high-temperature synthesis. 

Friedmann, F. Jensen, J.A. Some Factors Influencing the Formation and Propagation of Foams in Porous Media in Proc. 56th. SPE Calif. Regional Meeting, Society of Petroleum Engineers Richardson, TX, 1986, paper SPE 15087. 

Copolymerizations analogous to free-radical reactions occur between mixtures of monomers which have more or less the same e values [Table 9-1). The copolymerizations of styrene and dienes have been particularly studied in this connection. The simple copolymer equation (Eq. 7-13) applies to most of these systems, but the reactivity ratios will vary with the choice of solvent and positive counterion because these factors influence the nature of the propagating ion pair. 

In the following section we shall discuss the structure of steady, plane, one-dimensional, gaseous detonations. Factors influencing detonation propagation velocities are considered in Section 6.2. Important unsteady and nonplanar aspects of detonation phenomena are treated in Section 6.3. Detonations in media that are not purely gaseous will be discussed in Section 6.4. Since the material on detonations is too extensive to be developed fully here, the reader is directed to the literature cited above for further details. 

Factors Influencing Propagation Pathways (abstraction vs. scission reactions vs. rearrangement) of LOO and LO ... 

Another factor influencing band intensities in photoelectron spectroscopy is the angular distribution of photoelectrons. This means that band areas in the photoelectron spectrum depend on the angle (a) between the directions of photon and electron propagation. These photoelectron distributions depend on the energy of the electrons and on the nature of the orbital from which they are ejected. The number of electrons Nj ejected per unit solid angle in a specific direction by unpolarized radiation is given by... 

Termination. Just as peroxy radicals are key to the propagation sequence, so the bimolecular recombination of these radicals is the major termination process in the unstabilized polymer. The existence of an intermediate tetroxide has been established in solution (25). Several factors influence the competitive pathways of subsequent decomposition to form alcohols, ketone and singlet oxygen or to form alkoxy radicals which can couple before separation from the reaction center to form a peroxide. This latter process is a route to crosslinking in the case of polymeric peroxy radicals. The effect of steric control, viscosity and temperature have been studied in solution. However, in the solid phase the rates of bimolecular processes which require the mutual diffusion of the reactant groups will be limited by the diffusion process. As a standard, we have assumed a value close to that determined from oxygen absorption (26) and by ESR spectra (27) for oxidized polypropylene films. 

Another important factor affecting molecular weight distribution arises from reversibility of propagation. Its influence was discussed earlier in the section dealing with the thermodynamics of propagation, see p. 25 and Ref. 205. 

Flaws, their shape, and their propagation are the central themes of this chapter. The various aspects of brittle failure are discussed from several viewpoints. The concepts of fracture toughness and flaw sensitivity are discussed first. The factors influencing the strengths of ceramics are dealt with in Sec. 11.3. Toughening mechanisms are dealt with in Sec. 11.4. Section 11.5 introduces the statistics of brittle failure and a methodology for design. 

There is a theoretical optimum for spiking samples to achieve the best precision for the ratio measurements. The error propagated by this measurement factor alters as one moves away from the theoretical optimum. This error propagation factor can be calculated from the isotope system being measured and is dependent on the isotopic abundances in the natural sample and the isotopically enriched (spike) material. The error propagation factor is therefore the theoretical factor influencing the precision of the ratio measurements, as a function of the closeness to the calculated optimum spike. 

This important result shows that adsorption in fixed beds is a phenomenon of propagation of concentration waves and that the nature of the equihbrium isotherm is the main factor influencing the shape of the breakthrough curve (Fig. 

There are several variants of the DCR theory differing from one another by the way in which account is taken of the physical factors influenced by the diffusion control on the description of elementary reactions rate. As a rule, the main factor influenced is the bimolecular chain termination process. The constant rate of chain termination is considered as a fnnction of the macroradical s mobility, their length [9-14], free volume [12,15-17] or characteristic viscosity of monomer-polymeric system. However, with the aim of explaining the auto deacceleration stage, the efficiency of initiation and constants of rate chain propagation are also considered to be functions of the macroradical s mobility [12,15,18]. 

We can now simunarize a few important points dealt with so far. Three factors influence stereoregularity during chain propagation ... 

From a great number of experimental results, Magee and McAlevy revealed the abundance of factors influencing the rate of surface flame propagation. 

Molecular orientation is another important factor influencing mechanical properties of coextruded films (11). Biaxial orientation can greatly improve film strength. However, uniaxial or highly unbalanced orientation causes poor transverse properties, which result in easy splitting of coextruded films in the machine direction. This tendency may occur even when a relatively thin layer responds to unidirectional orientation and propagates failure to thicker adjacent layers. 

In the terminal model it is assumed that the terminal unit of a propagating polymer radical is the only factor influencing its reactivity, and that side reactions are not significant. As a result, there are only four types of propagation reaction in the free-radical copolymerization of any two given monomers (Mi and M2) ... 

For risk assessment, the prediction of the pressure wave load upon buildings and industrial structures is very important. This requires the detailed knowledge of the factors influencing the flame propagation process. However, detailed and systematic investigations cannot be performed in real industrial structures. For this reason it is desirable to perform experiments in a model system with the possibility of varying many parameters systematically. The scale-up of the results to real structures must be undertaken on the basis of similarity laws. 

As noted above, the key factor influencing polymer length in these chain reactions is the competition between propagation and termination. One can expect that it will be crucial to exclude any impurities that can react with the growing radical chain and terminate the polymerization, if you want high MW polymer. On the other hand, if smaller molecular weights are desired, judicious addition of inhibitors and chain transfer agents could be useful. 

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