Vacuum systems Classifications

Pressure/vacuum, 435, 466 Vacuum systems, 343 Absolute pressure conversions, 363 Air inleakage, 366 Calculations, 366-375 Dissolved gases release, 368 Estimated air inleakage, table, 366 Evacuation time, 371 Maximum air leakage, chart, 367 Specific air inleakage rates, 368 Temperature approach, 375 Classifications, 343 Diagrams, 380 Pressure drop, 353 Pressure levels, 343, 352 Pressure terminology, 348 Pump down example, 381 Pump down time, 380 Thermal efficiency, 384 Valve codes, 26... 

The surface extended X-ray absorption fine structure (SEXAFS) method can use either an electron or an ion detection signal (Koningsberger and Prins, 1988). The classification of analytical techniques may be considered in terms of incident and emitted radiation, resolution, and sensitivity, according to Table 4.7, which lists eight of the many possible techniques (Briggs and Seah, 1990 Buckley, 1981 Watts, 1990). Many of the surface analysis techniques were introduced into many laboratories over the years of 1968 to 1970. This resulted from the maturing of clean vacuum systems which could achieve pressures, down to 10"8 Pa. At these low pressures, it is possible to obtain and maintain atomically clean surfaces. 

Ion mobility spectrometry (IMS) is an instrumental method where sample vapors are ionized and gaseous ions derived from a sample are characterized for speed of movement as a swarm in an electric field [1], The steps for both ion formation and ion characterization occur in most analytical mobility spectrometers at ambient pressure in a purified air atmosphere, and one attraction of this method is the simplicity of instrumentation without vacuum systems as found in mass spectrometers. Another attraction with this method is the chemical information gleaned from an IMS measurement including quantitative information, often with low limits of detection [2 1], and structural information or classification by chemical family [5,6], Much of the value with a mobility spectrometer is the selectivity of response that is associated with gas-phase chemical reactions in air at ambient pressure where substance can be preferentially ionized and detected while matrix interferences can be eliminated or suppressed. In 2004, over 20000 IMS-based analyzers such as those shown in Fig. 1 are placed at airports and other sensitive locations worldwide as commercially available instruments for the determination of explosives at trace concentration [7],... 

For purposes of classification we divide the several materials of the experimental unit into three groups. These are the materials used in the individual parts of the vacuum system, the materials used for connecting its parts, and the specimen and its support. 

For Case 2, each DVP requires 72.66 kWh of electricity, and operating cost savings due to this modification are US 257 801/year. Installed cost of two DVPs, based on vendor quotation, is US 400 000. So, payback period for this retrofit modification is 1.6 years. Thus, replacing the existing SJEs by DVPs is attractive for low capacities and non-hazardous applications such as a steam turbine s surface condenser vacuum system. DVPs are efficient, they require less electricity and so modification required at the substation is minimal. They are very compact and can be installed at ground level or on elevated platforms. Depending on the area classification of their location, explosion-proof motors may be required. 

At the basic level CVD reactors fall into two classifications—open and closed reactor systems. In the closed CVD system the precursors are loaded into the CVD chamber together with the specimens to be treated. The system is then closed and the temperature increased to initiate the chemical process. The process continues for a time sufficient to produce the required effect. The temperature is then reduced to ambient so that the reactor may be opened and the specimens removed. This reactor design is frequently used for the purification of metals and chromizing parts. The dominant type of CVD reactor is the open type. Flowing precursors continuously enter this reactor and the gaseous by-products of the chemical process are continuously removed from the reactor (usually with a vacuum pump) and appropriately treated for discharge into the environment. 

If applied to the reference state normal order enables us immediately to recognize those terms which survive in the computation of the vacuum amplitudes. The same applies for any model function and, hence, for real multidimensional model spaces, if a proper normal-order sequence is defined for all the particle-hole creation and annihilation operators from the four classes of orbitals (i)-(iv) in Subsection 3.4. In addition to the specification of a proper set of indices for the physical operators, such as the effective Hamiltonian or any other one- or two-particle operator, however, the definition and classification of the model-space functions now plays a crucial role. In order to deal properly with the model-spaces of open-shell systems, an unique set of indices is required, in particular, for identifying the operator strings of the model-space functions (a)< and d )p, respectively. Apart from the particle and hole states (with regard to the many-electron vacuum), we therefore need a clear and simple distinction between different classes of creation and annihilation operators. For this reason, it is convenient for the derivation of open-shell expansions to specify a (so-called) extended normal-order sequence. Six different types of orbitals have to be distinguished hereby in order to reflect not only the classification of the core, core-valence,... orbitals, following our discussion in Subsection 3.4, but also the range of summation which is associated with these orbitals. While some of the indices refer a class of orbitals as a whole, others are just used to indicate a particular core-valence or valence orbital, respectively. 

There are several types of interfaces that are of great practical importance and that will be discussed in turn. These general classifications include, solid-vacuum, liquid-vacuum, solid-gas, liquid-gas, solid-liquid, liquid-liquid, and solid-solid. From a practical standpoint, solid- and liquid-vacuum interfaces are of little concern. They are most often encountered in the context of theoretical derivations, since the absence of a second phase simplifies matters greatly, or in studies of high-vacuum processes such as deposition, and sputtering. The true two-phase systems (assuming that a vacuum is not considered to be a true phase ) are the ones which are of most importance in practical applications and that are addressed in most detail here. A list of commonly encountered examples of these interfaces is given in Table 2.1. 

Dense-phase conveying, also termed "nonsuspension" conveying, is normally used to discharge particulate solids or to move materials over short distances. There are several types of equipment such as plug-phase conveyors, fluidized systems, blow tanks, and, more innovative, long-distance systems. Dilute-phase, or dispersed-phase conveyors, are more versatile in use and can be considered the typical pneumatic conveying systems as described in the literature. The most accepted classification of dilute-phase conveyors comprises pressure, vacuum, combined, and closed-loop systems. 

An unaccelerated, halogenated system for the manufacture, principally by hand-lay or spray/projection, of fire retardant mouldings meeting the M2 (French) classification. Can also be employed for cold-press moulding and vacuum bag moulding. 

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