Frequency effects

From Equation (14.2), the only frequency-dependent part of Kerr constant is the dielectric anisotropy. For an LC mixture, the frequency dependent dielectric constants c// and Cxcan be described by the Cole-Cole equation [42]  

For a rod-like compound, ex has a much higher relaxation frequency than 8// due to its shorter dipole length in the direction perpendicular to molecular axis [43]. Thus in the low frequency region, the relaxation of e//, as described by the real part of Cole-Cole equation, is noticeable. 

Since the Kerr constant is linearly proportional to As, Li et al. modify Equation (14.2) to describe the frequency-dependent Kerr constant as [44] 

The rate dependencies of the ferroelectric material properties are also reflected in the dynamics after fatigue. Initially, most of the domain system will be switched almost instantaneously [235], and only a small amount of polarization will creep for longer time periods [194]. A highly retarded stretched exponential relaxation was observed after bipolar fatigue treatment [235], and these observations correlated well with the thermally activated domain dynamics. If the overall materials response was represented in a rate-dependent constitutive material law 236], however, then a growing defect cluster size would retard the domain dynamics considerably. Hard and soft material behaviors were also representable as different barrier heights to a thermally activated domain wall motion, as demonstrated by the theoretical studies of Belov and Kreher [236]. 

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Erequencies from 1 kHz to 50 MHz are used for various appHcations (3). Ferromagnetic materials have a skin-effect response to eddy currents which restricts the penetration depth. Nonferromagnetic materials on the other hand can be inspected to greater depth. In 6061-T6 aluminum, for example, a cod having a 1-kHz frequency effectively penetrates the surface to a depth of 3.2 mm (1). The same probe in steel penetrates to a depth of 0.5... 

Amplitude equations and fluctuations during passivation, 279 Analytical formulae for microwave frequency effects, accuracy of, 464 Andersen on the open circuit scrape method for potential of zero charge, 39 Anisotropic surface potential and the potential of zero charge, (Heusler and Lang), 34... 

Light pulsing frequency, effect on photo currents, 474... 

Potential sweep measurements, with microwave frequency effects, 455 Pourbaix diagrams, applied to adlayers on copper, 93... 

Transport equation, for microwave frequency effects of the electrode, 465 Trasatti... 

Except for samples at dump, a significant frequency effect is observed on Q1/Q2 versus strain graphs, in such a manner that the 0.5 Hz data envelop the 1.0 Hz ones. The higher the frequency, the... 

Kono, M., Kumagai, S., and Sakai, T., Ignition of gases by two successive sparks with reference to frequency effect of capacitance sparks. Combust. Flame, 27, 85 1976. 

The frequency effects are studied in the cylindrical geometry (R = 0.08 m, L = 0.027 m) at a constant power of 25 W, which corresponds to a volume power density 46 mW cm . The pressure is 120 mTorr with 45% SiHa and 55% H2. It is found that the RF voltage at this power scales with the frequency as Vrfv p = C, with C a constant. Because the induced displacement current increases with the... 

Various irradiation parameters were investigated, such as the types of organic additives, intensity of the ultrasound, dissolved gas and distance between the reaction vessel and the oscillator. In the case of frequency effects, other irradiation systems were used. The details are described in the section of effects of ultrasound frequency on the rate of reduction. 

The rate of Au(ffl) reduction should have a correlation with the cavitation efficiency at these frequencies. Therefore, the result of Fig. 5.8 suggests that maximum amounts of reductants are sonochemically formed at 213 kHz in the presence of 1-propanol. The existence of an optimum frequency in the sonochemical reduction efficiency would be explained as follows. As the frequency is increased, the number of cavitation bubbles can be expected to increase. This would result in an increase in the amount of primary and secondary radicals generated and an increase in the rate of Au(HI) reduction. On the other hand, at higher frequencies there may not be enough time for the accumulation of 1-propanol at the bubble/solution interface and for the evaporation of water and 1 -propanol molecules to occur during the expansion cycle of the bubble. This would result in a decrease in the amount of active radicals. Furthermore, the size of the bubbles also decreases with increasing frequency. These multiple effects would result in a very complex frequency effect. 

In Chapter 2, ENDOR (electron-nuclear double resonance) was briefly described. To perform an ENDOR experiment it is necessary to apply both a radiofrequency and a microwave frequency, effectively performing simultaneous NMR and ESR, respectively, on the sample. The experiment is performed at a fixed magnetic field, with the ESR saturating frequency centered on a... 

In addition, the effects of pulsatile flow cannot be ignored. One measure of the impact of oscillary flow is the Wcmersley parameter (a) a= h/2tt f/v where r is the tube radius, f the frequency of oscillation and v is the kinematic viscosity of the fluid (Wcmersley, 1955). The degree of departure from parabolic flow increases with and frequency effects may become important in straight tubes when a > 1 (Ultman, 1985). For conditions of these experiments, a exceeds one to beyond the third generation. 

High-Frequency Effects and the Importance of Input Decoupling... 

From the above calculations, the discharge frequency effect on the growth rate of the film can be explained qualitatively. 

Fig. 4) is physically more reasonable. As a practical matter, as k is increased, the calculation becomes increasingly unreliable because of the severely truncated basis set. The important point is that inclusion of a low frequency effective solvent mode can nicely rationalize the observed characteristics of the C T ion. Similar improvements may be anticipated in analyzing intervalence bands in other systems. 

Hung, H.-M. and Hoffmann, M.R. Kinetics and mechanism of the sonolytic degradation of chlorinated hydrocarbons frequency effects, 7 Phys. Chem. A, 103(15) 2734-2739, 1999. 

The water proton NMRD profiles of diferric iron transferrin (55) (Fig. 8) indicate a field dependent electron relaxation time with x of about 1.2 x 10 s. The fit must be done by taking into account a static ZFS, which results in a D parameter of about 0.2 cm and EjD = 1/3. The presence of ZFS is indicated by the additional inflection in the profile at about 10 MHz. In the fit, two sets of electron relaxation times (relative to ZFS axes and to external magnetic field axes) were taken into account to describe the low and the high field experimental data, the SBM theory being inadequate to describe the field dependence of the electron relaxation over the whole range of frequencies. Effective electron relaxation times of the order of 10 ° s have... 

As discussed in the previous section, excited shear layers dispersed at a higher rate than the natural shear layer growth rate. The amount of increase depended on the excitation frequency and amplitude. It was difficult to assess the effect of amplitude due to the passive nature of the excitation technique, but the frequency effect was investigated by comparing the results obtained with various cavities [14]. The results will be discussed in this section along with two other issues. One deals with the compressibility effect such as extending the results to a higher convective Mach number and the other concerned with possible thrust penalty associated with the passive excitation method. 

D. Axelson These spectra were obtained at 57.9 MHz, but that s not the problem. We can measure correlation times regardless of the frequency. The correlation time at the glass temperature is very long. From a measurement of the correlation time we should be able to tell whether it is a true glass. In all these cases the correlation times are six to nine orders of magnitude lower than can possibly exist in a glass. For this reason I think the correlation between the NMR measurement and dielectric relaxation and dynamic mechanical do not relate one to one because of the frequency effects in the other measurements. 

J. Guillet But you would expect a frequency effect in this one as well, if only the frequency of the motion itself. 

These brain-stem regions are interrelated by diverse neuronal projections and are connected to adrenergic structures [Dampney et al. 1977 Marovitch et al. 1982], such as the locus coeruleus, which are postulated to play a role in panic attacks [Gorman et al. 1989]. Further, experimental evidence suggests that CCK interacts with these brain stem mechanisms in modulating respiratory and cardiovascular functions. Microiontophoretic application of CCK-8S to neurons of the nucleus tractus solitarius in cats decreased both neuronal firing and respiratory frequency, effects that were reversed by administration of CCK-4 [Denavit-Saubie et al. 1985]. 

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