Thermal equilibrium condition

The rectifier, or diode, is an electronic device that allows current to flow in only one direction. There is low resistance to current flow in one direction, called the forward bias, and a high resistance to current flow in the opposite direction, known as the reverse bias. The operation of a pn rectifying junction is shown in Figure 6.17. If initially there is no electric field across the junction, no net current flows across the junction under thermal equilibrium conditions (Figure 6.17a). Holes are the dominant carriers on the / -side, and electrons predominate on the n-side. This is a dynamic equilibrium Holes and conduction electrons are being formed due to thermal agitation. When a hole and an electron meet at the interface, they recombine with the simultaneous emission of radiation photons. This causes a small flow of holes from the jp-region... 

The term desorption is used in contrast to evaporation in cases in which a transition of a molecular or ion from the condensed into the gas phase is assumed to take place under non thermal equilibrium condition. The underlying idea is that at thermal equilibrium, temperatures for an evaporation would lead to a correspondingly high excitation of internal vibrational modes of excitation leading to fraigmentation of the molecule. As mentioned above, several characteristics of the ion spectra (2., 6.) cannot reasonably be fitted to an equilibrium temperature model. These properties seem to be the more pronounced, the higher the laser irradiance (i.e. usually the shorter the pulse) and are best documented for the LAMMA technique. Though metastable decay of ions is observed and will be discussed below, the decay rate for most of the ions is very small and decay... 

When Bi zero dimensional or lumped model [2, 11], On the other hand, if Bi 1, the fluid can be considered isothermal and Ts = Too, which changes the convection boundary condition to a thermal equilibrium condition. 

In a static magnetic field, each unpaired electron-spin of a free radical precesses about the axis parallel or antiparallel to the magnetic field (z-direction). The quantum state of the electron spin is expressed by a or p corresponding to these precessions. The population of the P spin state is larger than that of the a state by a Boltzman factor under the thermal equilibrium condition. so that the spin system has a total magnetization along the z-axis. The x-and y-components of the magnetic moments of electron spins are cancelled out under the thermal equilibrium condition because of the incoherence of the precession motion. 

In a-Si H, it is difficult to operate CCDs in the same mode as conventional SCCDs. This is because the ideal inversion at the p-type a-Si interface has not been observed as yet (Sugiura and Matsumura, 1982), and as for H-type a-Si H, whose interface can be inverted, the drift mobility of the signal charge (i.e., hole) is very low. However, the band gap of a-Si H is about 1.7 eV, which is much wider than that of a single-crystal silicon. This indicates that the carrier concentration in undoped a-Si H under thermal equilibrium condition is so low that the accumulation mode can store transient signals sufficiently long for CCD operation, as described later. 

Before the transfer starts, the energy distribution of electrons takes the form of a Fermi-Dirac distribution function. While the number of electrons is decreasing steadily with time, the distribution of electrons keep the form of a Fermi-Dirac distribution function. This constancy of the distribution is due to the fact that the capture rate of free electrons by the localized states is much faster than the loss of free electrons caused by the transfer when the occupation probability of localized states is not approximately one. Therefore, electrons are considered to be in their quasi-thermal equilibrium condition i.e., the energy distribution of electrons is described by quasi-Fermi energy EF. Then the total density t of electrons captured by the localized states per unit volume can be written as... 

When the populations of the two levels involved in a transition are determined by thermal equilibrium conditions, the Van Vleck Weisskopf line shape function may be... 

Whatever the detailed interpretation of these results may be in this particular case, the point to make here is that the ion mobility setup provides the opportunity to obtain true thermo chemical data, as experiments are carried out under thermal equilibrium conditions. 

Figure 7.1 Variations of temperature with depth for measured temperatures and for temperatures calculated for two assumed conductive thermal equilibrium conditions.

Between 349-452 C, at an initial total pressure of about one atmosphere, the rate of formation of phosgene from CO and Cl, under thermal, equilibrium, conditions is given (using the useful notation developed in Gmelin [781]) by the expression [218] ... 

Figure 7-34 shows the adiabatic flame temperature and the heat of explosion of HMX-CMDB propellants as a function of i (N02) under thermal equilibrium conditions. The adiabatic flame temperature, Tg, and the heat of explosion increases as (N02) increases, i.e., c(N02) increases with increasing i (HMX). The base matrix is composed of the mass fractions of NC 0.25, NG 0.65, and DEP 0.10. The nitrogen concentration of the nitrocellulose used is 12.2%, the mass fraction of N02 contained within the base matrix is (N02 0.496), and the heat of explosion is 4.76 MJ/kg. 

If the combustion products of propellants reach their thermal equilibrium conditions, the combustion temperature is determined theoretically as described in Chapter 2. However, combustion in a rocket motor includes incomplete combustion and the flame temperature falls below the adiabatic flame temperature. If one assumes that the flame temperature T varies with pressurepc in a rocket motor, T is expressed by... 

The effective media properties D , Df, D , and Ds, which include both the molecular (i.e., conductive) and the hydrodynamic dispersion components, are also modeled. Due to the lack of any predictive correlations for the nonequilibrium transport, local thermal equilibrium conditions are used. For the interfacial convective transport, the local Nusselt and Sherwood numbers are prescribed. The effect of the solid particles geometry must also be addressed [160],... 

Very little is known about the nature of rotational energy transfer in a collision between an electronically excited molecule and a ground-state atom or molecule. In the few reported studies the experimental method is fundamentally the same as that described at the beginning of Section III.A. An initial rotational distribution is established by narrow-band excitation. The fluorescence emission contour is recorded twice, under collision-free and thermal equilibrium conditions, and then again under conditions such that there is one collision during the lifetime of the excited state. The differences in the rotational contours of the three emission spectra are then used to infer the pathway of rotational energy transfer, and the rate of that transfer. Some examples of the emission spectra recorded under these conditions are shown in Fig. 22. Because of the small spacings between the rotational levels of polyatomic molecules most excitation sources prepare nonthermal superpositions of rotational states rather than pure rotational states, and this complicates interpretation of the observations. 

In the present study a normal shock wave was injected into the flow field of a single-component two-phase medium in its thermal equilibrium condition, and detailed measurements of the flow field behind a shock wave were conducted to measure vapor condensation and heat transfer characteristics associated with phase change of the medium. 

Nitrogen gas was used as a driver in the pressure range from 0.5 MPa to 5 MPa. To realize a single component two-phase thermal equilibrium condition in the low pressure chamber, a certain amount of pure liquid was filled after evacuating the chamber. Such common liquids as distilled water, ethanol, benzene, acetone and refrigerant-11(R-11), were examined, but in the this paper discussions are focused mostly on the results of R-11 and benzene because their shock wave structures are more distinctive due to their relatively high saturated vapor pressure at room temperature. It should be noted that these are both "regular" fluids... 

Fig. 4.8. Electrical resistivity of p-Cc. The solid points were measured under thermal equilibrium conditions and the open circles were taken on warming rapidly before /3-Ce transformed to a-Ce. The solid squares were measured on slow warming of a sample which had been rapidly cooled to 4 K (within 5 to 10 min). The solid circles were taken on slow cooling from 300 K. The insert shows p-Ce transforming to a-Ce on cooling (point A) and on warming (point B).

Gas phase interferences due to compound formation of the analyte element with a concomitant should not be very significant in ETAAS because a much longer time is available for dissociation compared to FAAS. It was shown by high-temperature equilibrium calculations that gas phase interferences at the temperatures used in ETAAS should actually be rather insignificant [18], The reason why the literature is nevertheless full of reports on such interferences is largely due to an improper use of this technique. Slavin et al. [19], based on the systematic work of L vov [20], introduced a concept which they called stabilized temperature platform furnace (STPF). It is in essence a package of measures which eliminates most nonspectral interferences in ETAAS by atomization under local thermal equilibrium conditions. 

By scanning the probe laser over one or more rotational branches of the product, the relative intensities of the lines in this excitation spectrum may be used to determine product rotational (and/or vibrational) state distributions. In order to arrive at fully quantitative answers, corrections have to be made for relative transition probabilities, fluorescence lifetimes of the excited state, and any wavelength-dependent detection functions (such as the detection system spectral response). But once this has been done, one can deduce the ground state distribution function(s) by examining the so-called excitation spectrum of a molecular species. For thermal equilibrium conditions, the level population /V, can be described using a Boltzmann distribution function with temperature as the most important parameter in its most general form this is... 

When the incident laser power changes, a new thermal equilibrium condition evolves. This is a relatively slow process, and the response time of a typical thermopile is of the order of 1 s before the meter reading has stabilized. Clearly, this constimtes a disadvantage when rapid changes in laser beam power are important to monitor. On the other hand, thermal sensors are very versatile and robust. They work over an extremely broad spectral range, offer very uniform spatial response, and respond linearly to a wide range of input powers. 

A further important aspect of optical pumping with a polarized laser is the selective population or depletion of degenerate M sublevels 17, M) of a level with angular momentum J. These sublevels differ by the projection Mtl of J onto the quantization axis. Atoms or molecules with a nonuniform population density N(J, M) of these sublevels are oriented because their angular momentum J has a preferred spatial distribution while under thermal equilibrium conditions J points into all directions with equal probability, that is, the orientational distribution is uniform. The highest degree of orientation is reached if only one of the (27+ 1) possible M sublevels is selectively populated. 

Contact potential The internal voltage that exists across a PN junction under thermal equilibrium conditions, when no external bias voltage is applied. 

The material will be taken electrically neutral (p = 0) in its unperturbed bulk region under thermal equilibrium conditions. 

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