Variations examples

Normalization attempts to remove technical variation in the data that is not attributed to biological or treatment related variation. Examples of technical variation include differences in dye incorporation, physical differences in fluorescence efficiency of incorporated dyes, print-surface irregularities, and print-... 

To properly understand CMP film thickness control, the CMP engineer should understand the sources of thickness variation and how they impact the total film thickness uniformity. Nonuniformity can be grouped in two categories—random variation and systematic variation. Examples of random variation include wafer-to-wafer (WTW), run-to-run (RTR), and some elements of within-wafer (WIW) variations. Elements of random variation add to the total thickness variation by their root mean square [19]... 

A number of fairly rugged on-line instruments are available to follow the emulsion density variations. Examples include nuclear instruments and instruments based on mechanical oscillator techniques (Kratky et aL, 1973). By utilizing the density difference between the unreacted monomer and the putymer (providing a reasonable difference exists) the reactor conversion can then be calculated via... 

As with buffers, ionizing groups on a protein surface are expected to be affected by cosolvents and temperature variations. Examples of potentiometric titration will be shown and discussed in Section IV. They were obtained with the following techniques adapted to mixed solvents and to subzero temperatures. 

Finally, the computer applies the half-reaction generators quite mechanically and will often produce several variants for one construction which to the chemist appear conceptually equivalent, such as alkylation by a b-halo- or an a,b-unsaturated carbonyl electrophile. Several such kinds of equivalent reactions may be removed from the total which the operator must finally look over. This allows him to see more clearly the different synthetic "ideas produced, without the distraction of excessive minor variations. Examples of these minor variations are clearly apparent in the reactions display of Figure 9, e.g., 4-40 and 4-42, or 4-40 and 4-44. 

Hexane is an easy example. The variations in acentric factors are much more pronounced for heavy polar or polarizable components. It comes as no surprise that the values reported from different sources are not identical. 

Table 5.4 gives the specific energies of selected organic liquid compounds. Compared with the isooctane chosen as the base reference, the variations from one compound to another are relatively small, on the order of 1 to 5%, with the exception of some particular chemical structures such as those of the short chain nitroparaffins (nitromethane, nitroethane, nitropropane) that are found to be energetic . That is why nitromethane, for example, is recommended for very small motors such as model airplanes it was also used in the past for competitive auto racing, for example in the Formula 1 at Le Mans before being forbidden for safety reasons. 

Within the same reservoir, we also observe variations of specific gravity from one well to another for example, 0.848 (38.4° API) and 0.861 (32.8° API) in the Ghawar field. 

Reservoir engineers describe the relationship between the volume of fluids produced, the compressibility of the fluids and the reservoir pressure using material balance techniques. This approach treats the reservoir system like a tank, filled with oil, water, gas, and reservoir rock in the appropriate volumes, but without regard to the distribution of the fluids (i.e. the detailed movement of fluids inside the system). Material balance uses the PVT properties of the fluids described in Section 5.2.6, and accounts for the variations of fluid properties with pressure. The technique is firstly useful in predicting how reservoir pressure will respond to production. Secondly, material balance can be used to reduce uncertainty in volumetries by measuring reservoir pressure and cumulative production during the producing phase of the field life. An example of the simplest material balance equation for an oil reservoir above the bubble point will be shown In the next section. 

In order to test the economic performance of the project to variations in the base case estimates for the input data, sensitivity analysis is performed. This shows how robust the project is to variations in one or more parameters, and also highlights which of the inputs the project economics is more sensitive to. These inputs can then be addressed more specifically. For example if the project economics is highly sensitive to a delay in first production, then the scheduling should be more critically reviewed. 

Projection radiography is widely used for pipe inspection and corrosion monitoring. Film digitisation allows a direct access to the local density variations by computer software. Following to a calibration step an interactive estimation of local wall thickness change based on the obtained density variation is possible. The theoretical model is discussed, the limitations of the application range are shown and examples of the practical use are given. The accuracy of this method is compared to results from wall thickness measurements with ultrasonic devices. 

The experimental investigations are carried out in order to get an idea about the variations of the visibility of the indications during practical inspections. The specimen where a test piece with spare eroded artificial defects (Width 25 pm depth d = 30, 60, 120 pm) and other specimen with natural cracks, a forged steering lever and a weld. As an example, in Fig 4 the steering lever with 2 cracks can be seen and below the dependance on the visibilty of a weak indication and a part of the bright indications on the field strenght H. 

As an example of the application of the method, Neumann and Tanner [54] followed the variation with time of the surface tension of aqueous sodium dode-cyl sulfate solutions. Their results are shown in Fig. 11-15, and it is seen that a slow but considerable change occurred. 

As a final example, similar spectroscopy was carried out for CO2 physisorbed on MgO(lOO) [99]. Temperatures were around 80 K and equilibrium pressures, as low as 10 atm (at higher temperatures, CO2 chemsorbs to give surface carbonate). Here, the variation of the absorbance of the infrared bands with the polarization of the probe beam indicated that the surface CO2 phase was highly oriented. 

Most microporous adsorbents have a range of micropore size, as evidenced, for example, by a variation in or in calorimetric heats of adsorption with amount adsorbed [227]. As may be expected, a considerable amount of effort has been spent in seeing how to extract a size distribution from adsorption data. 

It is not surprising, in view of the material of the preceding section, that the heat of chemisorption often varies from the degree of surface coverage. It is convenient to consider two types of explanation (actual systems involving some combination of the two). First, the surface may be heterogeneous, so that a site energy distribution is involved (Section XVII-14). As an example, the variation of the calorimetric differential heat of adsorption of H2 on ZnO is shown in Fig. 

There are many examples in nature where a system is not in equilibrium and is evolving in time towards a thennodynamic equilibrium state. (There are also instances where non-equilibrium and time variation appear to be a persistent feature. These include chaos, oscillations and strange attractors. Such phenomena are not considered here.)... 

As these examples have demonstrated, in particular for fast reactions, chemical kinetics can only be appropriately described if one takes into account dynamic effects, though in practice it may prove extremely difficult to separate and identify different phenomena. It seems that more experiments under systematically controlled variation of solvent enviromnent parameters are needed, in conjunction with numerical simulations that as closely as possible mimic the experimental conditions to improve our understanding of condensed-phase reaction kmetics. The theoretical tools that are available to do so are covered in more depth in other chapters of this encyclopedia and also in comprehensive reviews [6, 118. 119],... 

---