Zero crossover

The amplitudes of the Fourier transform u) are zero where fmxiu) = 0, i.e. no information at these positions in reciprocal space are transferred to the image. These positions are zero-crossover(s) of the CTF. The defocus value(s) can be estimated from the position(s) u of the CTF crossover, and C and X (Zou etal, 1996). 

Figure 8.16. Separation distance at the zero crossover of the total potential (rE=0) against dll for various nanocrystal-thiol systems. The separation distances in close-packed organizations of nanocrystals obtained from TEM are also shown. (Reproduced with permission from reference [30].)...

This problem can be avoided by using a zero-crossover-fired power controller. This is a time-proportioning system controlled by the temperature controller. Being zero-voltage fired, this controller s circuit is free of RF noise. In other words, the switching occurs when no voltage is on the line. 

Another type of power controller is the solid-state relay power controller. This controller is reliable and inexpensive. It is zero-crossover fired, thus it does not generate RFI. However, to use the controller at its rated current level, it must be provided with a good heat sink. 

Crossover distortion A distortion that results in an amplifier when an irregularity is introduced into the signal as it crosses through a zero reference point. If an amplifier is properly designed and biased, the upper half cycle and lower half cycle of the signal coincide at the zero crossover reference. Crossover frequency The frequency at which output signals pass from one channel to the other in a crossover network. At the crossover frequency itself, the outputs to each side are equal. 

The system of equations for the DMFC anode then differs from Eqs (2.1)-(2.3) only by the stoichiometry factor in Eq. (2.3), where 4F should be replaced by 6F. With this in mind, in the case of zero crossover we can use the relations for voltage loss r/ obtained in Chapter 2 for the anodic voltage loss. The value ct in these relations should be treated as the methanol concentration in the ACL. 

This is illustrated in Figure 4.28. In the case of zero crossover, (4.218) decreases with J and fi (4.219) remains constant (Figure 4.28(a)). In the logarithmic scale, the curves in Figure 4.28(a) are parallel straight lines. 

In the case of non-zero crossover, /it (4.222) tends to zero with J, while (4.221) tends to a constant value jg (Figure 4.28(b)). Furthermore, mean... 

Figure 4.28 The shape of the local current density along the channel for the indicated values of mean current density J in a cell, (a) the case of zero crossover (/ = 0), and (b) non-zero crossover = 0.333). In both cases, A = 1.5. Arrows indicate the evolution of the curve as J —> 0.

This value coincides with those obtained for / = 0 (cf. (4.219)). Physically, the regime of cross-linked feeding is equivalent to the case of an ideal membrane with zero crossover. Using (4.227) in (4.211) and (4.213), we... 

Weyer, L.G, Utilizing Zero Crossover Points in the Near Infrared Reflectance Analysis of Ind. J. Appl. Polym. ScL, 1986.31 2417-2431. 

The quality of Equation 4.248 can be checked by comparing this equation to the exact numerical polarization curve, following from the direct solution of the system (4.232) and (4.233). For the sake of comparison, zero transport loss is assumed in the ABL and zero crossover, therefore in Equation 4.248, Cmt = 1 is set. Figure 4.30 shows that the analytical curve works well up to the limiting current density. Further numerical tests show that Equation 4.248 only fails in a small vicinity of the adsorption-limiting current (Figure 4.30). 

Numerous publications, particularly by Stone [38, 39], describe the induced Cotton effects in dye complexes with acidic polysaccharides such as heparin, chondroitin sulfate, carboxy me thy 1-cellulose, pectic acid and hyaluronic acid [40—42]. Methylene blue is usually used for these investigations, as its metachromasy depends to a high degree on the polysaccharide structure, As an example of a 4-1 linked amino sugar, heparin with methylene blue has a metachromatic absorption maximum of X = 565 nm. It its ORD a trough appears at 587 nm ( 3), and the CD also shows an exciton split with a zero crossover at 578 nm. These observations indicate dipole coupling and a helical arrangement of the bound dye molecules. 

Scanned pulsed eddy current. This technique for application of eddy-current technology uses analysis of the peak amplitude and zero crossover of the response to an input pulse to characterize the loss of material. This technology has been shown to measure material loss on the bottom of a top layer, the top of a bottom layer, and the bottom of a bottom layer in two-layer samples. Material loss is displayed according to a color scheme to an accuracy of about 5 percent. A mechanical bond is not necessary, as it is with ultrasonic testing. The instrument and scanner are rugged and portable, using conventional coils and commercial probes. The technique is sensitive to hidden corrosion and provides a quantitative determination of metal loss. 

From the Nernst equation with unity reactant activity we can show the theoretical equilibrium potential, which is close to accurate for the SOFC but assumes zero crossover and only accounts for equilibrium effects. From experimental observation of a hydrogen PEFC, Parthasarathy and co-workers [30] found that... 

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