Measurement misleading

These conclusions can provide very valuable experimental clues as to which tests are most useful. For example, it might be impracticable to perform large numbers of tests, so can we omit some compounds Should we measure all these parameters, or are some of them useful and some not Are some measurements misleading, and not typical of the overall pattern ... 

A problem obviously exists in trying to characterise anomalies in concrete due to the limitations of the individual techniques. Even a simple problem such as measurement of concrete thickness can result in misleading data if complementary measurements are not made In Fig. 7 and 8 the results of Impact Echo and SASW on concrete slabs are shown. The lE-result indicates a reflecting boundary at a depth corresponding to a frequency of transient stress wave reflection of 5.2 KHz. This is equivalent to a depth of 530 mm for a compression wave speed (Cp) of 3000 m/s, or 706 mm if Cp = 4000 m/s. Does the reflection come from a crack, void or back-side of a wall, and what is the true Cp ... 

We should mention here that using just similarity or dissimilarity in a similarity measure might be misleading. Therefore, some composite measures using both similarity and dissimilarity have been developed. These are the Hamann and the Yule measures (Table 6-2). A simple product of (1 - Tanimoto) and squared Eucli-... 

Analytical chemistry is often described as the area of chemistry responsible for characterizing the composition of matter, both qualitatively (what is present) and quantitatively (how much is present). This description is misleading. After all, almost all chemists routinely make qualitative or quantitative measurements. The argument has been made that analytical chemistry is not a separate branch of chemistry, but simply the application of chemical knowledge. In fact, you probably have performed quantitative and qualitative analyses in other chemistry courses. For example, many introductory courses in chemistry include qualitative schemes for identifying inorganic ions and quantitative analyses involving titrations. 

To solve a flow problem or characterize a given fluid, an instmment must be carefully selected. Many commercial viscometers are available with a variety of geometries for wide viscosity ranges and shear rates (10,21,49). Rarely is it necessary to constmct an instmment. However, in choosing a commercial viscometer a number of criteria must be considered. Of great importance is the nature of the material to be tested, its viscosity, its elasticity, the temperature dependence of its viscosity, and other variables. The degree of accuracy and precision required, and whether the measurements are for quaUty control or research, must be considered. The viscometer must be matched to the materials and processes of interest otherwise, the results may be misleading. 

Analysts must recognize that the end use as well as the uncertainty determines the value of measurements. While the operators may pay the most attention to one set of measurements in making their decisions, another set may be the proper focus for model development and parameter estimation. The predilec tion is to focus on those measurements that the operators Believe in or that the designers/con-trollers originally believed in. While these may not be misleading, they are usually not optimal, and analysts must consciously expand their vision to include others. 

The difficulty in accurately estimating the degree of local concentration remains one of the principal reasons susceptibility to SCC in a specific environment or circumstance is difficult to predict. Measurement of nominal stresses or levels of corrodent in the bulk environment can be quite misleading as predictors of SCC susceptibility. 

Exhibits 2-5 and 2-6 are modified sample lists of programs and elements for an actual company (here called Xmple, Inc.) drawn from the files of Arthur D. Little. These are in addition to the PSM requirements shown in Exhibit 2-4. You should develop similar lists for your company. These can usually be obtained from PSM and ESH manuals or the specialist staff who support the programs and elements. Be careful to make sure you understand the scope of each program, as the titles can sometimes be a little misleading. For example, spill response may cover only measures to be taken to stop further spillage, while containment and clean-up are covered under emergency response. 

The reader may now recall the discussion in Section 5.3, Position and Height of the Energy Barrier, on correlations of rates and equilibria of the same reactions and the interpretation of the slope a from such LEER as a measure of the position of the transition state along the reaction coordinate. It will now be apparent why the term Breasted coefficient is applied both to this quantity and also to the slope of LEER according to Eqs. (7-58) and (7-59). The interpretation of a and P from Eqs. (7-58) and (7-59) as measures of fractional progress along a reaction coordinate may be misleading when the reaction is complex, and caution is appropriate. - pp- 38-41... 

Although government officials attempted to educate the public and military personnel about atomic civil defense, in retrospect these efforts seem hopelessly naive if not intentionally misleading. Army training films advised soldiers to keep their mouths closed while obser"ving atomic test blasts in order to not inhale radioactive flying dirt. Civil defense films used a friendly animated turtle to teach schoolchildren to duck and cover during a nuclear attack—that is, duck under their desks and cover their heads. Such measures, of course, would have offered pitiful protection to those in the blast zone. 

For the application of solid electrolytes in batteries it is essential to characterize the materials carefully. These measurements may be easily misleading and are often incorrectly interpreted. It is therefore vital that the correct arrangements and procedures are applied. 

One facet of kinetic studies which must be considered is the fact that the observed reaction rate coefficients in first- and higher-order reactions are assumed to be related to the electronic structure of the molecule. However, recent work has shown that this assumption can be highly misleading if, in fact, the observed reaction rate is close to the encounter rate, i.e. reaction occurs at almost every collision and is limited only by the speed with which the reacting entities can diffuse through the medium the reaction is then said to be subject to diffusion control (see Volume 2, Chapter 4). It is apparent that substituent effects derived from reaction rates measured under these conditions may or will be meaningless since the rate of substitution is already at or near the maximum possible. 

Solution viscosity measurements have sometimes been utilized as qioality control tests for this polymer. Chromatographs of three samples that showed Identical intrinsic viscosities (0.8 g/dl) in toluene are shown in Figure 9. These chromatographs indicate that the identical viscosities are the result of different combinations of high and low MW components. These three polymer samples probably have significantly different physical properties and if viscosity measurments alone are utilized for quality control purposes, they may be quite misleading. 

It is usual to have the coefficient of determination, r, and the standard deviation or RMSE, reported for such QSPR models, where the latter two are essentially identical. The value indicates how well the model fits the data. Given an r value close to 1, most of the variahon in the original data is accounted for. However, even an of 1 provides no indication of the predictive properties of the model. Therefore, leave-one-out tests of the predictivity are often reported with a QSAR, where sequentially all but one descriptor are used to generate a model and the remaining one is predicted. The analogous statistical measures resulting from such leave-one-out cross-validation often are denoted as and SpR ss- Nevertheless, care must be taken even with respect to such predictivity measures, because they can be considerably misleading if clusters of similar compounds are in the dataset. 

Another problem can arise if the probes and monitors are working properly but the probe is placed improperly (this is very common in natural gas transmission pipelines). Then the probe does not measure the needed conditions and environment. The data obtained by the probe will not tell the whole story and can in fact give very misleading results. 

Suppose we wish to measure the position of a particle whose wave function is W(jc, i). The Bom interpretation of F(x, as the probability density for finding the associated particle at position x at time t implies that such a measurement will not yield a unique result. If we have a large number of particles, each of which is in state /) and we measure the position of each of these particles in separate experiments all at some time t, then we will obtain a multitude of different results. We may then calculate the average or mean value x) of these measurements. In quantum mechanics, average values of dynamical quantities are called expectation values. This name is somewhat misleading, because in an experimental measurement one does not expect to obtain the expectation value. 

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