Conduction regime

This indicates that the intensity signal increases linearly with the incident power. In this case, for which the applied voltage is negative, it is said that the photodiode is working in the photo conduction regime. 

As was shown by G. Helmholtz [1], in a purely viscous regime the energy dissipation, and hence the drag as well, are minimal. Similarly, it may be shown that heat transfer is minimal in a purely conductive regime in a fluid at rest. 

But it is easy to see that the same results will be valid for any other means of heat transfer as well, for example, by a cold flow of explosive mixture blowing over the igniting surface. It is only necessary that within a thin boundary layer near the igniting surface—within several units variation of 6 and —the influence of the gas motion not be felt, and a purely conductive regime take place (one corresponding to the plane case so that... 

The occurrence of the two clearly defined conductivity regimes was interpreted by the predominant role of QSE at low temperature (Tenergy barriers in the smallest granules which contact clusters of bigger size. For T> Tt x A, the barriers are smeared out by the temperature, the conductivity is metallic, while at low temperatures, electrons can tunnel through the barrier and the conductivity is temperature independent like the barrier transmittance. 

As expected for a (DT-TTF)+1/2 cation-radical, thermopower measurements indicate a hole transport for (DT-TTF)2[Au(mnt)2], which behaves like a semiconductor with a slight change in the conductivity regime 220 K. Diffuse X-ray scattering studies show that the donors dimerize along the b stacking direction, two DT-TTF molecules sharing one electron. Since Au(mnt)2 is... 

Figure 26 (a) Single-crystal optical reflectance data for organic conductions with decreasing conductivity from top to bottom (from Ref. 95) (b) optical reflectance of (TMTSF)2PF6 at different temperatures in the conducting regime (from Refs. 95 and 98) (c) anisotropy of the optical reflectance (from Ref. 98) (d) optical reflectance of p(ET)2I3 (from Ref. 97). 

Fig. 7.7. Relation between the conductivity prefactor and activation energy for different conduction regimes described in the text.

Nuclear spin-lattice relaxation conducting regime. As for the spin sector in the conducting regime, an approach to the 1-D exponent can be attempted looking at the spin-lattice relaxation rate for which the 2k° contribution should become predominant at low temperature where 0deviation from linearity below 150 K or so (Fig. 11), signaling the onset of 2k fluctuations. These AF fluctuations become even more visible when T, is plotted... 

For the second group of compounds formed at lower temperature, two conductivity regimes can be observed. The first conductivity break appears at a different temperature for each compound, has a smaller magnitude, and also spreads over a 40-50 K temperature range. 

The semiconducting character of molecular junctions, expressed by the low conduction regime at low bias followed by a conduction threshold, and the subsequent conduction spectrum beyond this threshold, are manifestations of the discrete quantum level structure of small molecular systems. However, the small system nature of molecular junctions inevitably expresses itself in the appearance of noise and relatively poor reproducibility. 

Finally, the system (5.26) has a stable homogeneous fixed point which is characterized by negative voltage u and almost zero current density J. This point corresponds to the non-conducting regime of the DBRT, which is beyond the scope of the present study. 

FIGURE 432 Korpela s [162] plot of Rar governing the stability of the conduction regime in a vertical rectangular parallelepiped cavity with W/L a 5 and H/L a 40. For Pr < 12.7, the instability leads to stationary, horizontal axis rolls for Pr > 12.7, it leads to unsteady, vertically traveling waves. 

Cylinders With Vertical Axes. In the case of vertical cylinders, the height H of the cylinders also plays a role, and so do the two flat end faces, which are assumed to be adiabatic surfaces. Several studies have been done on this problem Kumar and Kalam [169] have provided a summary of much of that work. For laminar flow and outside the conduction regime, they recommend the equation... 

Vertical Surfaces. Analyses and measurements related to transient heat transfer on vertical surfaces have been reviewed by Ede [79], For negligible solid heat capacitance, results of analyses are discussed for step changes in wall temperature and in surface heat flux, and for periodic specified temperature or flux, as well as for other prescribed variations. Most recent analyses have confirmed the estimate of Siegel [252] that the local time for departure from the conduction regime at distance position x from the leading of a vertical flat plate after a step change in wall temperature is... 

Horizontal Wires. Attention is restricted to horizontal cylinders (see Fig. 4.39 for nomenclature) that are nearly isothermal on any plane perpendicular to the axis of the cylinder (this will occur if hDlkw < 0.1, where h is the average heat transfer coefficient on the outside surface and kw is the thermal conductivity of the wire). If the wire is suddenly heated by switching on a current, its temperature response in the conduction regime for a given heat capacity ratio (pcp)H,/pCp can be found [30, 218]. The trends are schematically illustrated in Fig. 4.39 for different values of Ra. ... 

The end of the conduction regime at time xD (see Fig. 4.39 for definition of t) is associated with the top-heavy instability (see the section on horizontal rectangular parallelepiped and circular cylinder cavities) that occurs along the separation line on the top of the cylinder [272]. The dimensionless time xD for air, water, and alcohol was adequately correlated by... 

Following the conduction regime there is a transition period, during which convection becomes established, to a quasi-steady regime in which the bulk temperature of the fluid in the enclosure gradually approaches the wall temperature. It is heat transfer in this quasisteady regime that is the subject of this section. 

A density matrix approach makes it possible to examine more general models for systems like this [38,39]. For instance, unlike superexchange theory, this approach admits models that include strong couplings between the closely associated species in the intercalated DNA/donor-acceptor complex. More important, the density matrix description allows a proper treatment of quantum coherences, which is critical in bridging the tunneling and free-conduction regimes of transport. On the one hand,... 

The starting point is the analytical expression for the neutral curve in planar alignment with realistic rigid boundary conditions in the conductive regime... 

The homeotropic geometry also allows for the appearance of structures with a secondary spatial periodicity - chevrons - in the conductive regime at voltages considerably larger than Uc [43]. Such type of chevrons, which are characterized by a periodic arrangement of defect chains, have been observed before exclusively in the dielectric regime. 

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