The assumption that k values are constant over the entire duration of the reaction breaks down for termination reactions in bulk polymerizations. Here, as in Sec. 5.2, we can consider the termination process—whether by combination or disproportionation to depend on the rates at which polymer molecules can diffuse into (characterized by kj) or out of (characterized by k ) the same solvent cage and the rate at which chemical reaction between them (characterized by kj.) occurs in that cage. In Chap. 5 we saw that two limiting cases of Eq. (5.8) could be readily identified [Pg.361]

Process variables do not change G and, therefore, Mj- is constant over modest ranges of operating conditions. [Pg.350]

If the latent heat of vaporization is then assumed to be constant over the temperature range of interest, equation 6 can be integrated to give the Clausius-Clapeyron expression [Pg.233]

If the oxidizing gas is pure oxygen, and iNi2+ remains approximately constant over the oxide thickness [Pg.262]

In the region where > 1 then if the interparticle force is assumed to be constant over thi integration time step the following result is obtained [van Gunsteren et al. 1981] [Pg.405]

Electrical properties of acetal resin are collected in Table 3. The dielectric constant is constant over the temperature range of most interest (—40 to 50°C). Table 3. Electrical Properties of Acetal Resins [Pg.57]

Oxygen occurs free in the atmosphere (21% by volume. 23 by weight). The proportion is constant over the earth s surtace it is also constant for many miles upwards, because the turbulence of the atmosphere prevents the tendency for the lighter gases, for example helium, to increase in amount at higher altitudes. [Pg.260]

The effect of increasing gas rate is to increase /cg and decrease 0g, with the result that tends to be constant over a range of gas rates. [Pg.1382]

Rotameters require no straight runs of pipe before or after the point of installation. Pressure losses are substantially constant over the whole flow range. In experimental work, for greatest precision, a rotameter should be cahbrated with the flmd which is to be metered. However, most modern rotameters are precision-made so that their performance closely corresponds to a master cahbration plot for the type in question. Such a plot is supphed with the meter upon purchase. [Pg.897]

The fin efficiency is found from mathematically derived relations, in which the film heat-transfer coefficient is assumed to be constant over the entire fin and temperature gradients across the thickness of the fin have been neglected (see Kraus, Extended Suiface.s, Spartan Books, Baltimore, 1963). The efficiency cui ves for some common fin configurations are given in Figs. Il-3(k7 and 11-30 , [Pg.1052]

Economic Aspects. The Dow Chemical Company and Aqualon Co. are the only hsted principal producers of EC and HEEC products woddwide. Consumption has remained constant over the past several years, and the products ate not expected to grow in the future. Production is estimated at 5000 t/yr, roughly equally divided between The Dow Chemical Company and Aqualon Co. As with other cellulose ethers, the price for EC and HEEC varies by grade. [Pg.278]

Hibemia-Chemie has described a vapor-phase process that passes fresh and recycled 85 wt % phosphoric acid over a catalyst of hydrochloric acid-leached bentonite impregnated with phosphoric acid. Catalyst activity was claimed to remain constant over a period of one year at the following conditions (126) [Pg.406]

Capacitors. The outstandingly low dielectric loss of parylenes make them superior candidates for dielectrics in high quality capacitors. Furthermore, their dielectric constant and loss remain constant over a wide temperature range. In addition, they can be easily formed as thin, pinhole-free films. Kemet Flatkaps are fabricated by coating thin aluminum foil with Parylene N on both sides and winding the coated foils in pairs (62). [Pg.442]

Equation (12-46) may be solved by trial and error or graphically to estimate the true values of H, and t and, hence, the ac tual drying rate. The values of X and depend on the value of but can generally be considered constant over the range of temperatures usu ly encountered in air diying. [Pg.1191]

Electrical Properties. AH polyolefins have low dielectric constants and can be used as insulators in particular, PMP has the lowest dielectric constant among all synthetic resins. As a result, PMP has excellent dielectric properties and alow dielectric loss factor, surpassing those of other polyolefin resins and polytetrafluoroethylene (Teflon). These properties remain nearly constant over a wide temperature range. The dielectric characteristics of poly(vinylcyclohexane) are especially attractive its dielectric loss remains constant between —180 and 160°C, which makes it a prospective high frequency dielectric material of high thermal stabiUty. [Pg.429]

Breakeven charts present a snapshot of the present situation by means of graphs which are generally drawn in the manner shown in Figs. 9-2, 9-3, and 9-4. Since the lines are straight, this implies that Cs, Cy , and Aee will remain constant over the range of variation of R, which is of interest. The values would be based on the production rate currently achieved (or scheduled), since all the data are available from [Pg.860]

The prefactor M(T), also called a frequency factor, has units of inverse seconds. It may have a weak dependence on temperature. Some theoretical models predict a variation with, but such variation is frequently ignored and M is taken as constant over limited temperature ranges. The prefactor M is often [Pg.513]

Data for determining the size of natural-draft towers have been presented by Chilton [Proc. Inst. Elec. Eng., 99,440 (1952)] and Rish and Steel (ASCE Swuposium on Thermal Power Plants, October 19.58). Chilton showed that the duty coefficient Df of a tower is approximately constant over its normal range of operation and is related to tower size by an efficiency factor or performance coefficient as follows [Pg.1169]

Properties. Xanthan gum is a cream-colored powder that dissolves in either hot or cold water to produce solutions with high viscosity at low concentration. These solutions exhibit pseudoplasticity, ie, the viscosity decreases as the shear rate increases. This decrease is instantaneous and reversible. Solutions, particularly in the presence of small amounts of electrolyte, have exceUent thermal stabiHty, and their viscosity is essentially constant over the range 0 to 80°C. They are not affected by changes in pH ranging from 2 to 10. [Pg.436]

For flow past a cyhnder, the vortex street forms at Reynolds numbers above about 40. The vortices initially form in the wake, the point of formation moving closer to the cylinder as Re is increased. At a Reynolds number of 60 to 100, the vortices are formed from eddies attached to the cylinder surface. The vortices move at a velocity slightly less than V. The frequency of vortex shedding/is given in terms of the Strouhal number, which is approximately constant over a wide range of Reynolds numbers. [Pg.667]

A number of simulation methods based on Equation (7.115) have been described. Thess differ in the assumptions that are made about the nature of frictional and random forces A common simplifying assumption is that the collision frequency 7 is independent o time and position. The random force R(f) is often assumed to be uncorrelated with th particle velocities, positions and the forces acting on them, and to obey a Gaussiar distribution with zero mean. The force F, is assumed to be constant over the time step o the integration. [Pg.405]

See also in sourсe #XX -- [ Pg.148 , Pg.149 ]

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