Coefficients emittance

Coefficients i (, cp, and (3 vary within a range from 0 to 1. The coefficient value depends on the heated surface temperature and emittance, and can be estimated from Table 7.2. 

The absorption coefficient k depends in general on wavelength (A). For large nl, e approaches 1 - a perfect emitter. This limit generally occurs at turbulent flames of about 1 m in thickness. 

CNTs are also valuable as field emitters because they have a small virtual source size [30], a high brightness, and a small positive temperature coefficient of resistance [31]. The latter means that they can run hot under high emission currents, but not go into thermal runaway. Emission from nanotubes can be visualized by electron holography in a TEM [32],... 

Tantalum is used widely, although in small quantities in the electronics industry in electrolytic capacitors, emitters, and getters. The corrosion resistance of tantalum has been compared with that of glass. Additionally, the metal has a high heat-transfer coefficient and is easy to fabricate. Consequently, it finds use in equipment that must resist strong corrosive... 

Rates of decomposition of the molecular ions of aminotriazoline stereoisomers have been determined over the time range tens of picoseconds to microseconds using a blade emitter and a double-focussing mass spectrometer [399]. The predominant process at the shortest times was, in all cases, loss of molecular nitrogen. The stereoisomers decomposed at very different rates, which was interpreted in terms of differing rate coefficients, k(E), arising from different amounts of steric strain. 

One can define four coefficients or hybrid parameters hu, / 12, h2i, and I122 and assume a linear dependence of the emitter voltage vE and the collector current ic on the emitter current iE and the collector voltage vCr as follows ... 

Here, the requirement of high values of the electron-hole recombination coefficient requires double injection from two Ohmic contacts to produce two SCL currents meeting and annihilating each other somewhere in the emitter within a narrow recombination zone (w [Pg.231]

Molecular energy, permittivity, molar absorption coefficient (absorptivity), emittance... 

We will express the IR emitted by a leaf at a temperature 74eaf using the Stefan-Boltzmann law (Eq. 6.18a), which describes the maximum rate of radiation emitted per unit area. For the general emission case we incorporate a coefficient known as the emissivity, or emittance (e)y which takes on its maximum value of 1 for a perfect, or blackbody, radiator. The actual radiant energy flux density equals (Tact )4 (Eq. 6-18b), which is the same as actual temperatures to describe... 

Actually existing emitters are not black bodies. More realistic values may be calculated according to the Planck-Kirchhoff law, Eqs. 3.3-4 to 3.3-8. Table 3.4-4 shows typical molar decadic absorption coefficients for infrared absorption bands of character-... 

The sensitivity of the measurement of diffusion coefficients in solids depends primarily on the method applied. By the radiation-absorption method mentioned above, diffusion coefficients down to about 10 ° cm s can be measured in the case of p emitters and down to about 10" cm s in the case of a emitters. The recoil method makes it possible to measure diffusion coefficients down to the order of 10 cm s . Relatively low sensitivity D > 10 cm s ) is achieved with the method of mechanical slicing, whereas diffusion coefficients down to about 10 cm s are obtained with the method of dissolution in steps. Mechanical slicing and dissolution in steps have the advantage that the actual concentration in the solid is obtained. 

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