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Vibrational temperature

The proteetive system is independent of the eontrol system and provides proteetion from over-speed, over-temperature, vibration, loss of flame, and loss of lubrieation. The over-speed proteetion system generally has a trans-dueer mounted on the aeeessory gear or shaft, and trips the gas turbine at approximately 10% of maximum design speed. The over-temperature system has thermoeouples similar to the normal temperature eontrols with a similar redundant system. The flame deteetion system eonsists of at least two ultraviolet flame deteetors to sense a flame in the eombustion eans. [Pg.639]

The control and subproducts for the instrumentation are governed by the general technical requirements for the other subproducts in the system. In addition, to fulfill all the general technical requirements, the encapsulation and protection of the environments in which the subproducts are used have to be considered, including danger of explosion, pollution, moisture, temperature, vibration, influence on heating and cooling, etc. See (Table 9.7). [Pg.774]

The design of support structures (not covered by this Code) and of supporting elements (see definitions of piping and pipe-supporting elements in para. GR-1.5) shall be based on all concurrently acting loads transmitted into such supports. These loads, defined in para. IP-2.1, include weight effects, loads introduced by service pressures and temperatures, vibration, wind, earthquake, shock, and displacement strain [see para. IP-6.1.3(a)]. [Pg.113]

The magnetic moments of Fe, Co, and Ni clusters with sizes up to 700 atoms have been measured by Billas et al.1,2 Those measurements were made under conditions where the clusters exhibit super-paramagnetic behavior for low cluster temperatures (vibrational temperature Tv b = 78 K for Ni and Co clusters and 120 K for Fe clusters). Their results are shown in Figure 1. As... [Pg.195]

Both these results favorably compare with experimental measurements of these thermochemical properties. It is important to note that vibrational contributions to both S and Cp are negligible in this example. However, for molecules containing heavy atoms, i.e., with low vibrational frequencies, and those with a large number of atoms, i.e., with many degrees of vibrational freedom, as well as at high temperatures, vibrations would be expected to contribute significantly to both S and Cp. [Pg.119]

Check the site for fulfillment of the manufacturer s recommendations (utilities such as electricity, water, and gases, and environmental conditions such as humidity, temperature, vibration level, and dust). [Pg.260]

At high temperatures, vibrational states must also be included in the partition sum above. The nuclear weights are gj for hydrogen we have, for example, gj = 1 for even j, and gj = 3 for odd j. However, we mention that in low-temperature laboratory measurements as well as in astrophysical applications, para-H2 and ortho-H2 abundances may actually differ from the proportions characteristic of thermal equilibrium (Eq. 6.53). In such a case, at any fixed temperature T, one may account for non-equilibrium proportions by assuming gj values so that the ratio go/gi reflects the actual para to ortho abundance ratio. Positive frequencies correspond to absorption, but the spectral function g(co T) is also defined for negative frequencies which correspond to emission. We note that the product V g a> T) actually does not depend on V because of the reciprocal F-dependence of Pt, Eq. 6.52. [Pg.309]

The thermal internal energy function calculated at 298.15 K [E — 0] is also listed in Table 8.1. The translational and rotational contributions are found using Eqs. 8.80 and 8.82, respectively. The vibrational contributions (Eq. 8.84) are much less, as expected. Mode 2 makes a significant contribution to the total internal energy at this temperature. Vibrational modes 5 and 6 also make smaller, but nonnegligible, contributions. The electronic contribution was calculated directly from Eq. 8.76. Through application of Eq. 8.118, the total enthalpy is [H — Ho] - 11146.71 J/mole. [Pg.364]

Measurements also commonly involve random errors. These are errors whose size and direction differ from measurement to measurement that is, they are unpredictable and unreproducible. They are commonly associated with the limited sensitivity of instruments, the quality of the scales being read, the degree of control over the environment (temperature, vibration, humidity, and so on), or human frailties (limitations of eyesight, hearing, judgment, and so on). We shall say much more about random error later in this chapter. [Pg.44]

At low enough temperatures vibrational fine structure of aromatic chromophores may be well resolved, especially if they are embedded in a suitable matrix such as argon or N2, which is deposited on a transparent surface at 15 K. This matrix isolation spectroscopy77166 may reveal differences in spectra of conformers or, as in Fig. 23-16, of tautomers. In the latter example the IR spectra of the well-known amino-oxo and amino-hydroxy tautomers of cytosine can both be seen in the matrix isolation IR spectrum. Figure 23-16 is an IR spectrum, but at low temperatures electronic absorption spectra may display sharp vibrational structure. For example, aromatic hydrocarbons dissolved in n-heptane or n-octane and frozen often have absorption spectra, and therefore fluorescence excitation spectra, which often consist of very narrow lines. A laser can be tuned to excite only one line in the absorption spectrum. For example, in the spectrum of the carcinogen ll-methylbenz(a)anthrene in frozen octane three major transitions arise because there are three different environments for the molecule. Excitation of these lines separately yields distinctly different emission spectra.77 Likewise, in complex mixtures of different hydrocarbons emission can be excited from each one at will and can be used for estimation of amounts. Other related methods of energy-... [Pg.1293]

At higher temperatures vibrational levels with n >0 are also occupied, so that the temperature dependence of the vibronic intensity in emission is given by 1 + , where is the average value of ri given by... [Pg.5]

Figure 7.X2. (a) Lattice low-temperature vibration spectrum of solid rt-hex-ane. Vertical lines indicate Raman active frequencies, (b) Calculated dispersion curves of low-frequency vibrations. (From Takeuchi et al. [1980].)... Figure 7.X2. (a) Lattice low-temperature vibration spectrum of solid rt-hex-ane. Vertical lines indicate Raman active frequencies, (b) Calculated dispersion curves of low-frequency vibrations. (From Takeuchi et al. [1980].)...
In Section 2.1, we remarked that classical thermodynamics does not offer us a means of determining absolute values of thermodynamic state functions. Fortunately, first-principles (FP), or ab initio, methods based on the density-functional theory (DFT) provide a way of calculating thermodynamic properties at 0 K, where one can normally neglect zero-point vibrations. At finite temperatures, vibrational contributions must be added to the zero-kelvin DFT results. To understand how ab initio thermodynamics (not to be confused with the term computational thermochemistry used in Section 2.1) is possible, we first need to discuss the statistical mechanical interpretation of absolute internal energy, so that we can relate it to concepts from ab initio methods. [Pg.66]

In order to advance the usefulness of theoretical calculations in broader applications, the computations should be carried out for a system that describes experimental conditions as accurately as possible. To do this, consider the following topics for a description of a system beyond using a single static structure at 0 K conformational averaging of static gas phase structures (this has been partially addressed already in Sect. 3), solvent effects on static structures, zero-point and finite temperature vibrational averaging, and molecular dynamics (MD) or Monte-Carlo (MC) sampling without and with solvation. [Pg.35]

Zero-Point and Finite Temperature Vibrational Averaging... [Pg.41]

Petrovic AG, Polavarapu PL (2005) Structural transitions in polyriboadenylic acid induced by the changes in pH and temperature vibrational circular dichroism study in solution and film states. J Phys Chem B 109 23698-23705... [Pg.230]

Ionic formulation of both the compounds has been supported from their low-temperature vibrational spectra. [Pg.152]

Low temperature vibrational transfer data were analyzed by fitting the time-dependent relative vibrational populations to a kinetic model defined by the rate equations... [Pg.155]

The mechanical durability of an EX-22,350/S.5 ceramic preconverter was assessed in the high-temperature vibration test, using an exhaust gas generator and an electromagnetic vibration table, under the following conditions ... [Pg.53]

In the simplest adiabatic case with an orbital singlet term, potential energy of the crystal lattice is parabolic with one minimum point. At low temperatures, vibrations of the lattice are localized at the bottom of this well, and as a rule, the so-called harmonic approximation applies. This corresponds to the so-called polaron effect and brings us to the concept of electrons coated with phonons. [Pg.714]


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