Primary elements

Pig. 6. A 0.3-mm-diameter cosmic spherule coUected from the ocean floor. The particle is composed of oUvine, glass, and magnetite and has a primary element composition similar to chondritic meteorites for nonvolatile elements. The shape is the result of melting and rapid recrystaUi2ation during... 

The composition of an optoelectronic memory card (eg. Laser Card of Drexler Technology Corp.) (162) is outlined in Figure 21 (163). Primary elements are polycarbonate foils with thicknesses of 250 to 400 )Tm, respectively, that are employed because of their high operating temperature and their good mechanical, optical, and dielectric characteristics. The OMC can be used as a ROM or a WORM media. Both possibiUties of information deposition can be used separately or in combination. 

For the purpose of this chapter, instrumentation will be considered everything from the primary element monitoring the controlled variable through the control valve performing the throttling action. The process equipment interacts with the instrumentation to provide the process... 

LThe compensated flow transmitter determines the process flow it converts this quantity to a signal that is proportional to the process flow and sends it to the flow controller. The transmitter could be a pneumatic device using a venturi primary element, with compensation for pressure by a pressure element and compensation for tern perature by a thermocouple. The output would be a pneumatic sic nal that is proportional to weight flow. 

Transducer (Converter)—A device that receives a signal from one power source and outputs a proportional signal in another power system. A transducer can act as a primary element, transmitter or other device. 

Primary Element—A device that measures a process variable. 

Transmitter-A device that senses a process variable through a primary element and puts out a signal proportional to that variable to a remotely located instrument. 

Process Variable or Actuation Controlling Devices Measuring Alarm Devices Devices Primary Elements Wells Glass Devices for Visual Observation... 

The source of Au was most likely the gold crucible generally used for crystal growing. A comparative analysis of the crystal energy dispersive spectrometry using a SEM (q.v.) identified the primary elements, plus a very weak peak for Au and no indication of Cr and Fe traces. This demonstrates the advantage of PIXE over SEM in terms of sensitivity for trace element detection. 

The contributions of different stars to nucleosynthesis depend on their initial mass and chemical composition, their mass loss history in the course of evolution and effects of close binaries (especially SN la). When mass loss is small, as is believed to be the case for low metallicities, the distribution of primary elements (those synthesized directly from hydrogen and helium) in ejecta from massive stars is mainly the result of hydrostatic evolution with some modifications to deeper layers resulting from explosive nucleosynthesis in the final SN outburst, classically... 

Table 7.3. Primary element production from massive stars with modest mass loss...

Unlike the age-abundance relation, the distribution function of stellar abundances of primary elements is independent of past rates of star formation as long as instantaneous recycling holds, and this makes it a potentially powerful clue to the evolutionary histories of stellar populations. 

The predictions of ratios of primary elements formed by massive stars are not specific to the Simple model that model just provides a convenient framework in which to discuss them. The case for other element ratios may be more complicated there is an illuminating discussion by Wheeler, Sneden and Truran (1989) who comprehensively review the older literature, and there is a more recent review by Me William (1997). Regarding the data in Figs. 8.1 and 8.2, all stellar nucleosynthesis models lead one to expect a nearly constant O/Ne ratio, but the O/S ratio could conceivably vary because sulphur is more affected by explosive (as opposed to hydrostatic) nucleosynthesis with a yield per star that is estimated not to increase greatly with the star s initial mass (Table 7.2 and references therein). Figure 8.2 provides little evidence for any variation in practice. 

Show that, in the simple inflow model described by Eqs. (8.46) to (8.52), the ratio of a secondary to a primary element is 4/3 times what it is in the Simple model at the same (primary) metallicity. 

Production of 6Li by a — a fusion in the ISM is a primary process, so that its interstellar abundance at low metallicities would be expected to track primary elements... 

The flow of fluids is most commonly measured using head flowmeters. The operation of these flowmeters is based on the Bernoulli equation. A constriction in the flow path is used to increase the flow velocity. This is accompanied by a decrease in pressure head and since the resultant pressure drop is a function of the flow rate of fluid, the latter can be evaluated. The flowmeters for closed conduits can be used for both gases and liquids. The flowmeters for open conduits can only be used for liquids. Head flowmeters include orifice and venturi meters, flow nozzles, Pitot tubes and weirs. They consist of a primary element which causes the pressure or head loss and a secondary element which measures it. The primary element does not contain any moving parts. The most common secondary elements for closed conduit flowmeters are U-tube manometers and differential pressure transducers. 

Other flowmeters are in common use which operate on principles differing from head flowmeters. Mechanical flowmeters have primary elements which contain moving parts. These flowmeters include rotameters, positive displacement meters and velocity meters. Electromagne-... 

The primary element of an orifice meter is simply a flat plate containing a drilled hole located in a pipe perpendicular to the direction of fluid flow as shown in Figure 8.2. 

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