Measurements atmospheric pressure

Solution of equation (6) requires two boundary conditions and an initial condition. The upper boundary condition at land surface is specified by the actual atmospheric pressure measurements at the field site. For the analytical solution presented in the following section, a sinusoidal pressure cycle at land surface was used as the upper boundary condition ... 

Pressure In most CVD processes, the pressures are described relative to standard atmospheric pressure measured at the earth s surface ( 14.7 lbs/in2 absolute or PSIA), equivalent to 760 Torr, 1000 mbar, or 100 kPa. 

Finally, repeat the complete procedure with Ar as the second gas. In addition to determining the diffusion coefficients at atmospheric pressure, measure one of them at half an atmosphere. 

The most recent determination, made using relative rate methods [101], gives a value approximately a factor of two higher than either the extrapolation of the low pressure data of Plumb and Ryan [102] or the atmospheric pressure measurement of Munk et al. [98]. However, it is close to the extrapolation of the low pressure data of Wagner et al. [108] made using variational RRKM methods. 

Fig. 2. Powder profile of solid C q at atmospheric pressure, measured on a diffractometer equipped with a position-sensitive detector (8) and a 1.5-kW sealed Cu source monochromatized by the (002) reflection of graphite (k = 1.54 A). The powder sample was containol in a Lindemann capillary tube (0.7 mm in diameter). Dots are the measured points (2 hours accumulation), and the solid curve is a least-squares fit to an fee lattice of uniform spherical shells. The best-fit parameters are a = 14.11 A and shell radius Rq = 3.5 A. This sample exhibits much less intensity in the low-angle shoulder of the (111) reflection.

Figure 12-3 A representation of Boyle s experiment. A sample of air is trapped in a tube in such a way that the pressure on the air can be changed and the volume of the air measured, is the atmospheric pressure, measured with a barometer. P = + P, Pj 2 atm-...

A Novocontrol Alpha-Analyzer (v=10 -10 Hz) was used for dielectric measurements, both at atmospheric and at high pressure. For atmospheric pressure measurements, a parallel plate capacitor separated by a quartz spacer (empty capacitance 90 pF) and filled by the sample was placed in the nitrogen flow Quattro cryostat (T= 100-3 60 K). For high pressure measurements, a sample-holder multi-layer capacitor (empty capacitance 30pF) was separated from the pressurizing fluid (silicon oil) by a Teflon membrane. The high pressure chamber (Cu-Be alloy), provided by UNIPRESS, was connected to a hydraulic pump able to reach 700 MPa, and controlled in the interval 195-360 K within 0.1 K by means of a thermally conditioned liquid flow. 

A much larger unit is the standard atmosphere (atm), the average atmospheric pressure measured at sea level and 0°C. It is defined in terms of the pascal ... 

A variety of manometers and other devices is available to measure the pressure of a fluid, each type useful in a particular pressure range. Some devices measure the pressure of the fluid directly. Others measure the differential pressure between the fluid and the atmosphere the fluid pressure is obtained by combining this measurement with the atmospheric pressure measured with a barometer. 

It is the aim of the present review to emphasize the pressure dependence of the activation quantities (A V and dA H/dp), which is not obtainable in atmospheric pressure measurements. 

The facilitated permeability of a feed mixture of 50 mole% ethylene and 50 mole% ethane at atmospheric pressure measured by Eriksen et al. (76) was 1000 Barrer compared with a value 2100 Barrer observed in the present work. However, the separation factor observed by Eriksen et al. of 470 was higher than that reported in the present work. Much higher ethylene permeabilities and separation factors were reported by Teramoto et al. (8). In that study, an ethylene permeability of 3 x 10 Barrer with a C2H4/C2H6 separation ctor of 1000 was obtained from a supported liquid membrane containing aqueous 4 M Ag Oa. The higher permeabilities observed by Teramoto are probably a result of higher ionic mobility in the supported liquid membrane. 

---