Fudge-factor

The concept of the fudge factor was introduced by Golay to describe such constants as (X), (y), (co) and (q) used by Van Deemter, Giddings and others in the 

Giddings made a stalwart effort to provide values for the different constants that would apply to diverse stationary phase and support conditions [2]. However, at best, his values are the closest estimates from an assumed set of conditions that may fit, to a greater or lesser extent, the properties of the actual stationary phase or support in use. In some cases, his constants may be used in column design and to help in the choice of those operating conditions that will provide the required 

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In summary, the rate theory provides the following equations for the variance per unit length (H) for four different columns. 

It should be noted that all the equations assume that the mobile phase is incompressible which will not be true for equations (23) and (24). It follows that equations (23) and (24) will require modification in order to be applicable to practical situations. It will also be shown in a later chapter that, from experimental data, (oo) 

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The contiguity factor, Cj is actually a so-called fudge factor used to make sense out of the comparison of experimental dataTwitlirtheore-tical predictions. This correlation factor is useful only when the data fall between the theoretical bounds. The concept of a contiguity factor, i.e.. 

Fudge factors built into internal support group estimates. 

This balance is not quite satisfied by the experimental data, so an adjustment is needed. Define material balance fudge factors by... 

Westfall, Richard S. Newton and the fudge factor. Science 179 (1973) 751-758. 

Both FJPa and Fm are independent of pressure, and z is essentially a fudge factor, which, Knudsen found experimentally, varies only slightly with pressure according to the empirical relationship... 

Note the values 0.1,0.3 and 0.5 are just fudge factors to give better estimates. 

As a working definition, the activity may be said to be the perceived concentration and is therefore somewhat of a fudge factor . More formally, the activity a is defined by... 

Activity coefficients. For nonideal liquids, Raoult s law must be modified to account for the nonideality in the liquid phase. The fudge factors used are... 

S = effectiveness factor, a fudge factor which varies betwen 0 and 1, and which accounts for the resistance to pore diffusion... 

The log transformation is by far the most common transformation, but there are several other transformations that are from time to time used in recovering normality. The square root transformation,., /x, is sometimes used with count data while the logit transformation, log (x/l — x), can be used where the patient provides a measure which is a proportion, such as the proportion of days symptom-free in a 14 day period. One slight problem with the logit transformation is that it is not defined when the value of x is either zero or one. To cope with this in practice, we tend to add 1/2 (or some other chosen value) to x and (1 —x) as a fudge factor before taking the log of the ratio. 

B. A. Boville and P. R. Gent, The NCAR Climate System Model, Version One, J. Climate 11 (1998) 1115-30 R. A. Kerr, Model Gets It Right— Without Fudge Factors, Science276 (1997) 1041. 

A fine flurry of fudge factors (AIChE Institute Lecture, 1997) Chem. Eng. Prog. (Being revised for publication). 

In the constructionist method, aromatic carbons are evaluated from benzene, a solute which has been measured more times than any other. When the phenyl ring is fused to others, as in naphthalene or anthracene, or when it is joined to another, as in biphenyl, there is a change in the effective polarity of the pi electron cloud, and a slight but significant positive correction factor is introduced. Critics may disparagingly refer to these as fudge factors/ but these factors have been very helpful in distinguishing the solvation forces which operate in the two different phases (Taft, 1996). 

Such methods, although not considered as primary methods of analysis because of a remaining fudge factor , may be reasonable substitutes for exploitation in round-robin studies, for the production of usable RMs and for practical analysis. 

Note that here using the natural logarithm requires that K be a pure number, while it usually has the units of some power of concentrations. Note also that, to "keep us honest," activities and not concentrations should enter into Eqs. (6.2.14) or (6.2.19). In the pious but understandable desire to keep equations simple when the reagents interact in nonideal fashion, activity coefficients y can be used as premultipliers to [A], [B], etc. (e.g., yA, yB, etc.) to convert concentrations to activities these empirical "fudge factors" are themselves dependent on temperature, on concentration, and on electrolyte strength and hide within them the departure from ideal behavior. 

Attempts to solve Equation (6) numerically, using the existing "software of high-powered computers, are useless. Solutions can be readily obtained, assuming a variety of initial conditions and disturbance patterns, but they cannot be fitted into the patterns of Tables II and III, without the introduction of "fudge factors." The essence of our development is that it is necessary to introduce such factors, like the parameters n, K1, and K2 of Equation (9), to explain the... 

Figure 4-15, so only a fraction,/, of initially formed radicals start chains. Therefore, the kinetic equation for the rate of initiation has to be modified to include this fudge factor (Equation 4-24). 

To conclude this section we will simply note that the relationship given above in Equation 11-36 does not work well for polymer solutions. A comparison of calculated values of x to those obtained experimentally has led to the suggestion that a fudge factor df about 0.34 be included (Equation 11-39) ... 

This fudge factor is actually an average obtained from various studies, and so is only useful as a rough guide.)... 

However the size of this term gets smaller as the size of the molecules (mA, mB) gets larger. On the other hand, the x term is always positive and unfavorable to mixing in systems where the molecules interact through dispersion and weak polar forces only, as can more readily be seen if we write x in terms of solubility parameters (neglecting any fudge factors)—see Equation 11-37 above. 

Calculate the value of % for solutions of polystyrene in these solvents (use a fudge factor of 0.34). Indicate which solutions are likely to be single phase and which are likely to be phase-separated. Use Table 11-1 to calculate the solubility parameter of polystyrene from group contributions. 

A plot of the photocurrent quantum yield versus excitation wavelength is termed the photoaction or photocurrent action spectrum. These spectra are obtained at short-circuit in a two-electrode arrangement or with an external bias in a three-electrode configuration. The photocurrent quantum yield is defined as the number of electrons measured in the external circuit divided by the number of absorbed photons. It is experimentally difficult to calculate the number of absorbed photons and corrections for scattered or transmitted light often appear to be fudge factors that increase the uncertainty of the absolute photocurrent yield. Therefore, the incident photocurrent yield is often reported which represents a lower limit of the true photocurrent quantum yield. 

The tortuosity factor r is thus a plausible fudge factor and could be imagined to account also for the effect of the constrictions in pore diameter. Values of t ranging from 0.3 to 6 have been reported so that the ratio I/t may vary widely from 0.05 to I or more. However values of t less than I do not make good sense physically and arise from using too simplified a model to account for diffusion in much more complex structures. More complicated models are beyond our scope here, but references are given at the end of the chapter. 

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