Frequency sensitivity

Kaczmarek, L. K. Frequency sensitive biochemical reactions. Biophys. Chem. 1976, 4, 249-252. 

The electrolyte solution is stimulated by an electromagnetic field applied over the microwave region, and the dielectric response of the sample is then measured. The complex dielectric response is frequency sensitive and dependent on the square of the dipole moment of each species in solution. Both solvent molecules and dipolar ion-pairs contribute to the signal. Additional contributions arise from the polarizability... 

Measurements are generally made in terms of W/m or mW/cm. A radiometer spectral characteristics are determined by the detector head chosen and any filters used. These instruments may be frequency sensitive. 

Fatigues tests have been run on a series of ABS samples under reversed tension-compression at a stress amplitude of 27.6 MPa, at four different frequencies, viz. 0.02, 0.2, 2, and 21 Hz. The average fatigue lifetime as a function of frequency is shown in Fig. 46 and, for comparison purposes, the data for HIPS obtained at 17.2 MPa is also shown. The average fatigue life-time of ABS increases in a linear manner with frequency on this log-log plot. The rate of increase, however, is reduced compared to that of HIPS, or of PS (Fig. 15). The reduced frequency sensitivity is perhaps a result of a reduced magnitude of the p-transition in the SAN copolymer compared to that in PS. A reduced frequency sensitivity of FCP rate in ABS vs. a HIPS-modified PPO has also been noted... 

Fatigue lifetime increases with increase of test frequency, v, according to a power law relationship, for both PS and HIPS and the slope of the lop N-log v plot appears independent of stress ampHtude over the stress range investigated. Fatigue endurance also increases with frequency for ABS but its frequency sensitivity is less than that of HIPS. 

Figures 29 and 30 show typical growth rates for two high molecular cast sheets PMMA, one of them being frequency sensitive and the other one not frequency sensitive.

Fig. 29. Growth rates da/dn versus 8K, at 23 °C for a high molecular cast sheet PMMA showing frequency sensitivity (0.1, 1,11 and 100 Hz test). (PMMA Plexiglas G from Rohm and Haas company, USA). From Refs. and courtesy of Society of Plastics Engineers Edn.

Fig. 30. Growth rates da/dn versus 8Ki at 23 °C for another high molecular cast sheet PMMA that does not show frequency sensitivity (0.4, 2, 10 and 50 Hz test). (PMMA 233 from Rohm Company (Germany) From Ref. courtesy Dr. Dietrich Steinkopff Verlag...

EPR Research Center). Zero-field splittings in metal based systems can be overcome at these high microwave frequencies ( sensitivity for 10 spins). 

Obviously the factor relating Im(ZL) to A/s is proportional to 1/dq and, at the first glance, independent of the crystal cut. A/s is independent of k and hence of the electrode diameter as well. As consequence of Vq = 2dq/o the frequency shift remains dependent on Vq. The effect of wave velocity on the sensor s frequency sensitivity is dependent upon whether a certain resonance frequency or a certain crystal thickness is the (experimentally) given value. It can be easily demonstrated in the simplest case of pure mass sensitivity (Zl =ja>pcdc holds). Following Sauerbrey, the frequency sensitivity can be rewritten as ... 

In parallel with these experimental studies of PL for SQD suspensions, the role of the observed linewidth broadening has been examined. In particular, the linewidth broadening due to acoustic-phonon-assisted transitions is expected [1] to contribute to satellite lines in PL spectra that are downshifted by the acoustic phonon energies. Within the elastic continuum approach [6], the phonon mode frequencies sensitive to the boundary conditions at the SQD surface were calculated. The lowest-order spherical acoustic mode frequency for CdS for different matrix materials differ by as much as a factor of three for a given SQD radius. 

Note that differences between the positions of the peaks in the peak number plots are plotted as dots, and the number of dots appearing in each 3-cm interval are counted and plotted. The striking periodicity thereby revealed is interpreted as showing that the frequency sensitivities of the various biological receptors are evenly spaced. 

Transform die representation into a space that has more desirable properties log magnitude spectra follow the ear s dynamic range mel-scaled cepstra scale according to the frequency sensitivity to the ear log area ratios are amenable to simple interpolation and line-spectral frequencies show the formant patterns robustly. 

As indicated in connection with Eq. (11), the energy supply Sj may occur at any, or all, frequencies of the polar modes. The subsequent excitation of a particular mode, e.g., coi, then requires some time even when the total rate of supply exceeds o- The system thus possesses storing ability. One would expect, however, that this time is particularly short if the energy is supplied at the frequency of the mode that will be excited coherently. Furthermore, arising from the considerations of mode softening, this mode, when excited, may be detached from the band and hence provide a very frequency-sensitive target for further energy supply. Detailed calculations on this question have not been carried out yet. 

Frequency Compensation Frequency compensation is a very important property of the TPS that is not shared by the tapered R-Card. Since the TPS is a periodic surface, it is frequency sensitive, a property that may be exploited on a variety of broad band antenna applications. 

Since there is a time-temperature superposition for polymers, the frequency and temperature dependences of the acoustic properties are inversely related, so that decrease in temperature correspond to the effect of increases in frequency. This behavior is illustrated by comparing Fig. 60.5(a) and (b) which display the temperature and frequency sensitivity for two polymers [1]. Since measurements over a wide temperature range are more readily made than those over a corresponding frequency range, the combination of the data from measurements over a wide temperature range and a modest frequency range usually serve to define the entire spectrum. The frequency sensitivity of ultrasound... 

The resonant frequency of the quartz cavity has been observed to be highly dependent on several environmental factors, including temperature and external or internal stresses apphed to the quartz material. These factors can result in frequency sensitivities on the order of 100 ppm in some cases. This type of sensitivity would make precision frequency control apphcations extremely difficult without the use of fairly sophisticated control networks that would stabilize temperature and isolate the quartz oscillator from external vibration noise. Fortunately, however, a variety of crystal cuts have been discovered that result in a much lower sensitivity to temperature and stress effects. The stress compensated SC-cut (EerNisse, 1975) is described in Sec. 3.1.7. 

One of the early challenges of antenna design was to achieve the proper input impedance over the bandwidth of a single channel because antenna components are frequency sensitive. Since that time, modern antenna design has made it possible to achieve good response over multiple channels. 

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