Pressure range definitions

TABLE 43 Pressure Range Definitions as Used by the American Vacuum Society (AVS) in Units of Pa (the SI Unit for Pressure) and Torn See Table 4.1 for Conversion Factors. 

Mesophase that is thermodynamically stable over a definite temperature or pressure range. Note The range of thermal stability of an enantiotropic mesophase is limited by the melting point and the clearing point of an LC compound or by any two successive mesophase transitions. 

Tests showed that liquid lubricants do not even provide adequate lubrication in the lower Vacuums of space simulators. Solid lubricants, such as molybdenum disulfide, tungsten disulfide. and the soft metals have given better results. However, the known data about space lubricants are results of simulator measurements made in the pressure range of 10 s to 1C6 torr which does not simulate real space conditions, and therefore, these available data cannot be considered completely valid. It can be expected that definite data on lubricant performance in a vacuum will be obtained by conducting tests in a simulator that reaches the low 10"10 torr range. At this press level, the monolayer formation time is increased to at least several hours which will result in a sufficient time span for observing the metal... 

The data in Fig. 9.4-1 for the nitrogen-butane system show that the mixture compressibility is nearly a linear function of mole fraction at both low and high pressures, so thatEq. 9.4-2 is approximately satisfied at these conditions, but fails in the intermediate pressure range. If we nonetheless accept Eq. 9.4-2 as being a reasonable approximation over the whole pressu e range, we then have, from Eq. 9.4-1 and the definition of the partial molar volume, VfT, P, y) = Vi(7 , P) and, from Eq. 9.2-6,... 

Pressure effects on surfactant systems containing conventional liquid alkanes have not often been studied because of the very low compressibility of liquids. Conflicting results have been reported [38-40]. It is likely that the changes in cohesive energy density (solubility parameter) of the phases over the pressure ranges used were too low to produce definitive trends in phase behavior. The solubility parameter of compressed liquid propane, however, is moderately adjustable with pressure, and therefore a propane-brine-AOT system could be expected to show pressure-driven phase transitions [20,22,41]. 

Although the mathematical definition places the ideal-gas state at a single point (P = o, Z = i), from a practical point of view we will consider a gas to be in the ideal-gas state if the compressibility factor is sufficiently close to i. For calculations that do not require high accuracy we will assume a gas to be in the ideal-gas state if the compressibility factor is within 5% of the theoretical value of 1. The pressure range over which this approximation is valid varies with temperature. 

The definition is Atmospheric conditions exist if the absolute pressure-range is between 0.8 and 1.1 bar and the temperature is in the range from -20 to -1-60 °C. The directives to the explosion protection do not cover... 

Almost by definition macropores cannot be observed in the isotherm, at least until now. This is because the pore filling would occur at pressures too close to the vapor pressure,, to be reliably measured. This, however, may be changing. By using a differential technique and very good temperature control and handling methods Denoyel, Barrande and Beurroies [23] have been able to extend the reliable pressure range to 0.99985 of and measured porosity up to 12 qm The analysis method should be identical to that used for mesopore (lUPAC). 

Also shown in Figure 4.1 are the definitions used to describe the various pressure ranges (vacuum ranges). As these are not universally accepted, those from the American Vacuum Society (AVS) are used. These are defined in Table 4.3. 

Note Other definitions of the respective pressure ranges also exist. 

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