Conductivity high frequencies

The purpose of an input conducted EMI filter is to keep the high-frequency conducted noise inside the case. The main noise source is the switching power supply. Filtering on any of the input/output (I/O) lines is also important to keep noise from any internal circuit, like microprocessors, inside the case. 

Hamada et al. 1992 Saito et al. 1992), this increase of absorption is caused by high-frequency conductivity of the free carriers in metallic nanotubes. Relative intensities of the spectra of Fig. 11.7 we have found as a result of the diffuse reflection measurements of powders at low wavenumbers. The discussed above Drude approximations of the low-energy part of the absorption spectra are shown by dashed curves in Fig. 11.7. Comparison of the spectra 1 and 2 shows that hydrogenation decreases high-frequency conductivity of the SWNTs by one order of magnitude. 

Transitions between the competing phases existing at x = 1 /8 have been tracked by high-frequency conductivity measurements (F. Mayr et al., 2000) and exposure to X-rays has been shown (Casa et al., 2001) to induce conductive transitions with memory at temperatures T < Too-... 

As one can see from Fig. 3 (the spectral dependence of optical conductivity u(e) in the interval of interband transitions) the greatest changes are observed for the high-frequency conductivity, caused by yi > q (/ > /, ) transition [9-10], This... 

Each resonance-enhanced Raman mode has a counterpart in the IR spectrum, due to the pinning of charge oscillations. The amplitude mode model can be used to derive the doping-induced modes if a pinning constant a for the renormalization of the bare phonons is employed instead of the renormalization constant A for rc-electron interaction (Ehrenfreund et al., 1987). This procedure is very similar to the evaluation of Raman modes by Eq. 4.8-10, as indicated in Fig. 4.8-10. The high frequency conductivity cr(iu) is obtained from... 

Fiq. 33. High frequency conductance dispersion of potassium chloride... 

Note A quick diagnostic test for understanding a particular high-frequency conducted EMI problem (measured by a LISN at the inputs of the power supply) is to twist the output cables of the power supply tightly together (along with their respective return wires). This induces field cancellation (also called flux containment), thus reducing the radiation from the output cables (if present). 

ESA is directly proportional to the dynamic mobility, whereas UVP requires knowledge of the high-frequency conductivity of the slurry. For this reason, ESA is frequently used for routine analysis of powder slurries under processing conditions [75]. An example of the application of ESA to powder characterization is given in Fig. 4, where the effect of surface cleaning on a SisN4 powder is evidenced by a shift in pHiep of the aqueous slurry. This shift is caused by a reduction of the surface oxide layer thickness. 

Figure 5.14 shows how the high-frequency conductance varies with the low-frequency conductance at several different frequencies. 

Figure 5.14. High-frequency conductance response versus low-frequency specific conductance response. 

Reaction Rates. A fascinating application of high-frequency conductance is determining rates of reactions. The response must be related directly to the change in the composition of the solution. Thus, for example, the rapid rates of hydrolysis of esters have been determined, as well as the rates of some polymerization reactions. 

From (9.32), which shows that is determined by the least effective conductivity mechanism, it is evident that this static conductivity may be quite critically dependent upon the presence of proton-donor or proton-acceptor impurities and, in this sense, the behaviour of ice is quite analogous to that of electronic semiconductors like germanium or silicon. Mole fractions of impurity which are significant are of the order of io . The high-frequency conductivity and relaxation time t are, from (9.30) and (9.35), rather less sensitive to impurity content than is doping levels. The static dielectric constant depends on purity in a rather complex way, as we shall discuss presently. 

Since cr ctol for pure ice and since w+ increases rather slowly as hf is increased, we may expect from (9.30) that the high-frequency conductivity may be dominated by the effects of changes in (Tdl. Measurements by Jaccard (1959) show that, at -55 °C,... 

We have given perhaps undue attention to the mobile carrier mechanism because at one time it was assumed that the Na and K transport in excitable cell membranes occurred precisely via this mechanism. In 1965, Chandler and Meves undertook an experiment to assess the aforementioned specifics of the high-frequency conductance. A nerve fiber was placed in a solution containing no Na or K ions. This precluded direct current through the membrane. However, if there had been any mobile charged carriers in the membrane, the authors would have detected current on application of a variable field. The authors did not observe a detectable current under these conditions, from which it could be deduced that the transport systems of excitable membrane are structured as ion channels whose conductance is controlled by electric field. 

TABLE 15.3 Comparison of the DC and High-Frequency Conductivity Parameters for Selected PAN-CSA Films... 

There are, however, other measurement methods developed mainly for routine process control in radiation processing, such as high-frequency conductivity (oscillometric) analysis, spectrophotometric evaluation, and conductivity measurement. 

High-frequency conductivity (oscillometric) measurement. Oscillometry (Blaedel and Petitjean 1956), i.e., the high-frequency method of chemical analysis to measure or follow changes in the composition of chemical systems was introduced to measure absorbed dose... 

Cramer C, Funke K, Saatkamp T, Wilmer D, Ingram MD (1995) High frequency conductivity plateau and ionic hopping processes in a ternary lithium borate glass. Z Naturforsch A Phys Sci 50 613-623... 

Analysis of the reflection spectra led to the following high-frequency conductivities kq in 10 Q" -cm"i ... 

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