Ratios current

The current efficiency of an electrolytic process ( current) ratio of the amount of material produced to the theoreticaUy expected quantities. 

Current ratio—> FIG. 9-22 Probability of a given current ratio. 

Working-Capital Ratios Financial analysts make extensive use of ratios in assessing the economic health of a company. For evaluating the ability of a company to successfully maintain and develop its immediate business activities, analysts apply a current ratio and a quick (or acid-test) ratio, as given by... 

Althou a high current ratio is desirable, this may be achieved by having unnecessarily high inventories that bring no profit except when commodity prices are rising rapidly. The quick ratio is less misleading in this respect. 

As an example of a standardless bulk analysis by SNMS, a measurement of the complex Ni-based Hasteloy metal (NIST SRM 2402) is presented in Figure 3 and Table 1, in which the composition determined from ion-current ratios (not RSF corrected) is compared to the certified chemical composition. 

As A will be a function of current density, T will be a function of electrode area, and comparisons should therefore be made with cells of standard size. Equation 12.12 shows that high throwing indices will result when polarisation rises steeply with current (AE, AEj) and cathode efficiency falls steeply (cj >> f i)- The primary current ratio, P = affects the result because... 

Throwing indices measured in a Hull cell differ from those in a Haring-Blum cell because of the differences in geometry. In a Hull cell several pairs of points can be found which have the same primary current ratio, but for which M and hence T are found to vary because of polarisation changes. 

FET is ihe on-off current ratio, which indicates its ability to shut down the current, and is particularly relevant in applications such as active matrix displays and logical circuits. Because of the presence of p-n junctions at both the source and drain electrode, the on-off ratio of MOSFETs is in the I0y range [12J, while that of a-Si H TFT is limited to 106 [13], High mobility ensures high on-current and, hence, also contributes to a high on-off ratio. 

For the SECMIT mode the tip current response is governed primarily by K, Kg, y, and the dimensionless tip-substrate distance, L. Here, we briefly examine the effects of these parameters on the chronoamperometric and steady-state SECMIT characteristics. All chronoamperometric data are presented as normalized current ratio versus in order to emphasize the short-time characteristics, for the reasons outlined previously [12,14-16]. Steady-state characteristics, derived from the chronoamperometric data in the long-time limit, are considered over the full range of tip-substrate separations generally encountered in SECM. 

A huge shift is predicted in the ratio of doctor bills to pharmaceutical costs, from the current ratio of about 9 to 1 to a ratio of 1 to 1 in the next 25 years [12],... 

FIGURE 2.4. EC reaction scheme in cyclic voltammetry. Derivation of the rate constant from the anodic-to-cathodic peak current ratio in zone KO. In this example the scan is reversed 200 mV (at 25° C) after the peak. 

FIGURE 2.7. Double potential step chronoamperometry for an EC mechanism with an irreversible follow-up reaction, a Potential program with a cyclic voltammogram showing the location of the starting and inversion potentials to avoid interference of the charge transfer kinetics, b Example of chronoamperometric response, c Variation of the normalized anodic-to-cathodic current ratio, R, with the dimensionless kinetic parameter X. 

FIGURE 2.12. Double potential step chronoamperometry for an ECE (dashed line) and a DISP (solid line) mechanism. Variation of the normalized anodic-to-cathodic current ratio, RDps = [—ia(2tR)/ic(tR)]/(l — l/y/2), with the dimesionless kinetic parameter X — ktR. 

The fact that the normalized current ratio becomes negative at intermediate values of X with the ECE mechanism and not with the DISP mechanism stems from the same phenomenon as the one causing the tracecrossing behavior in cyclic voltammetry (Figure 2.9) (i.e., continuation of the reduction of C during the anodic scan). 

FIGURE 2.13. Radical-radical electrodimerization (Scheme 2.7). a Variations of the peak potential with the kinetic parameter, aj. h Procedure for determining the dimerization rate constant from the anodic-to-cathodic peak current ratio. 

As with the other reaction schemes involving the coupling of electron transfer with a follow-up homogeneous reaction, the kinetics of electron transfer may interfere in the rate control of the overall process, similar to what was described earlier for the EC mechanism. Under these conditions a convenient way of obtaining the rate constant for the follow-up reaction with no interference from the electron transfer kinetics is to use double potential chronoamperometry in place of cyclic voltammetry. The variations of normalized anodic-to-cathodic current ratio with the dimensionless rate parameter are summarized in Figure 2.15 for all four electrodimerization mechanisms. 

FIGURE 2.1 9. Homogeneous catalysis electrochemical reactions with the homogeneous electron transfer as a rate-limiting step. Variation of the current ratio ip/yfp with the kinetic parameter, A, far a series of values of the excess factor, y. From left to right, logy = 0, 0.3, 0.5, 1,1.5, 2. 

Calculation stability implies that At/Ay2 <0.5. The fulfillment of this condition may become a problem when fast reactions, or more precisely, large values of the kinetic parameter, are involved since most of the variation of C then occurs within a reaction layer much thinner than the diffusion layer. Making Ay sufficiently small for having enough points inside this layer thus implies diminishing At, and thus increasing the number of calculation lines, to an extent that may rapidly become prohibitive. This is, however, not much of a difficulty in a number of cases since the pure kinetic conditions are reached before the problem arises. This is, for example, the case with the calculation alluded to in Section 2.2.5, where application of double potential step chronoamperometry to various dimerizations mechanisms was depicted. In this case the current ratio becomes nil when the pure kinetic conditions are reached. 

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