Constants and Units

Many symbols, units, and constants are defined as they are introduced in the text. Those more commonly used are given here. 

In addition to lubricating the engines, turbine lubricants are also required to lubricate a number of associated systems such as auxiliary power units and constant speed drive units and to act as hydraulic fluids, for instance, in the propeller pitch control units of some turbo-props. 

To perpetuate the name of Curie, the quantity of emanation in equilibrium with one gn.m of radium was termed a curie. This is an inconveniently large amount and the milli-micro curie is frequently used as a practical unit. It is the quantity of emanation in equilibrium with one millionth of a milligram of radium. Since one-fiftieth of this can be detected with a sensitive electroscope, this method of detecting the presence of radio-elements is extraordinarily sensitive — more so even than the spectroscope. The above definition of the curie has now been superseded. In July 1950 the Joint Commission on Standards, Units and Constants of Radioactivity defined the curie as the quantity of any radioactive nuclide in which the number of disintegrations per second is 3-700 X io10. 

Obviously, because of the difference in the reactivity of styrene and DVB, the networks prepared by free radical copolymerization do not relate to such an ideal system with uniform distribution of DVB units and constant chain lengths between the junction points. Also, it was not possible to eliminate this serious defect by an anionic copolymerization of the comonomers. The anionic copolymerization has often been initiated by n- or sec-hutyl lithium [110-112]. Under such conditions, styrene is consumed faster than p-DVB, the monomer reactivity ratios being ri = 1.5S and r2 = 0.32. Therefore, DVB-enriched domains wUl form toward the end of the anionic process. On the other hand, the styrene—m-isomer reactivity ratio (r = 0.65 and r2 = 1.20) points to the local incorporation of m-DVB crosslinks into the initially formed copolymer [113, 114]. In addition, the anionic process is also accompanied by intramolecular cycUzation, similar to radical styrene DVB copolymerization [115,116]. 

National Institute of Standards and Technology A large amount of information about units and constants. 

The origin of the barn unit is thought to lie in the colloquialism as big as a barn, and was recommended in 1950 by the Joint Commission on Standards, Units and Constants of Radioactivity, because of its common usage in the USA (see page 9, The Atomic Nucleus, R. D. Evans, McGraw-Hill, New York, 1955). 

A cautionary word about units equilibriuin constants are usually expressed in nnits, because pressures and concentrations have nnits. Yet the argument of a logaritlnn must be dimensionless, so the activities in eqnation (A2.1.66). defined in tenns of the absolute activities (which are dimensionless) are dimensionless. 

Figure C2.3.3. Molecular packing of SDS monohydrate viewed as projected on the ac plane. This polymoriDh crystallizes in a triclinic cell with unit cell constants a, b and c of 10.423 A, 5.662 A and 28.913 A, respectively, and with a = 86.70°, (3 = 93.44°, y = 89.55°. There are four molecules per unit cell. Adapted from figure 2 of [18].

In a medium where the relative dielectric constant is e, the force between fixed chages at a definite separation is decreased by the dimensionless factor e. This is true regardless of the system of units and is incorporated into Eqs. (10.101) and (10.102) by dividing the right-hand side of each by e. ... 

For sources, units, and remarks, see Table 2-228. v = specific volume, mVkg h = specific enthalpy, kj/kg s = specific entropy, kJ/(kg-K) c = specific beat at constant pressure, kJ/(kg-K) i = viscosity, 10 Pa-s and k = tberni conductivity, VW(m-K). For specific beat ratio, see Table 2-200 for Prandtl number, see Table 2-369. 

The dimensional equations are usually expansions of the dimensionless expressions in which the terms are in more convenient units and in which all numerical factors are grouped together into a single numerical constant. In some instances, the combined physical properties are represented as a linear function of temperature, and the dimension equation resolves into an equation containing only one or two variables. 

Table 5-12 provides material balances for Cartesian, cylindrical, and spherical coordinates. The generic form applies over a unit cross-sectional area and constant volume ... 

Where ij. is defined as the kinematic viscosity (centistokes), and is a constant with a value of 2,213.8 in USCS units and 353.68 in SI units. An empirical relation for the Fanning friction factor is the Colebrook-White equation ... 

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