Error due to surface

Electrodeless conductivity is a technicjue for measuring the conductance of a solution using the electrical inductance principle at low frequencies. This method does not use contacting electrodes thereby eliminating maintenance and other errors due to surface effects created by coatings and fouling. The measurement enjoys widespread acceptance in the chemical process industries. Its history and a review of the literature have been presented here. 

The surface energy of a material is of fundamental interest, for example in the prediction of crystal morphologies and in understanding fracture. Accurate experimental measurements of the surface energy are difficult to perform. In fact, such measurements are mostly constrained to the determination of surface energies at high temperatures and are subject to numerous errors due to surface-active contaminants. For... 

In fact a sensor measures a flow and proceeds an integration of across a surface, which operates as a spacial lowpass filter. To avoid a critical deconvolution, the error due to this integration must be kept negligible. 

Appreciable errors may also be introduced by post-precipitation. This is the precipitation which occurs on the surface of the first precipitate after its formation. It occurs with sparingly soluble substances which form supersaturated solutions they usually have an ion in common with the primary precipitate. Thus in the precipitation of calcium as oxalate in the presence of magnesium, magnesium oxalate separates out gradually upon the calcium oxalate the longer the precipitate is allowed to stand in contact with the solution, the greater is the error due to this cause. A similar effect is observed in the precipitation of copper or mercury(II) sulphide in 0.3M hydrochloric acid in the presence of zinc ions zinc sulphide is slowly post-precipitated. 

Safety in use of x-ray equipment, 332 Sample, errors due to heterogeneity of surface, 172, 175... 

The error due to the simplification becomes significant when the thermal resistance in the solid PCM-layer (Figure 129) leads to a significant reduction below Tph at the heat exchanger surface. If the thermal resistance of the heat exchanger itself is neglected, then the driving temperature difference for the heat transfer is reduced by the ratio of the thermal resistances... 

The outer layer of samples (gloves, coveralls, socks, face wash, hand wash, and hat) allowed measurement of the complete dose encountered on the outside of the protective clothing without any subsampling. This eliminated any uncertainty or error due to the highly variable deposition of residues across the body surface. This is the upper limit of the potential dose that could be encountered by the operator, and it is used to assess the effectiveness of the protective clothing and other preventive measures. 

Parallax error is one of the main sources of error in liquid measurements. Figure 4.2 illustrates that the liquid surface in a container is not even, and a meniscus is formed. For most liquids the surface is concave. The uneven surface is due to surface tension, and if not read properly, may result in an error commonly known as parallax error. When a container with graduations for volumes has a liquid in it, the reading must always be made at the bottom of the meniscus. The parallax error is shown in Figure 4.2. 

One must be aware of the limits of this technique. Since the assessment of Z depends on frequency shifts of two modes, any minimal shift leads to errors due to substantial mechanical or thermal stresses. It is not necessary to mention that under such circumstances the Z match technique, too, leads to similar errors. Nevertheless, the automatic Z value determination of the Z match technique is somewhat more reliable regarding occurrence of errors because the amplitude distribution of the (102) mode is asymmetric over the active crystal surface and that of the (100) mode is symmetric. 

The U-tube must be uniform in diameter and scrupulously clean to avoid errors due to variations in surface tension. The best final stage for the cleaning process is to heat the evacuated tube to between 280 and 300 °C. A small constriction at the base of the U does not affect the measurements and prevents sudden surges of fluid, which can be destructive. 

For microwave radiation incident upon a slab from a direction perpendicular to its surface, a fraction of the energy will be reflected from the surface, Pr, depending upon its complex dielectric constant e. The main contribution to the magnitude of reflection however, is from the dielectric constant e. Errors due to neglecting e" are less than 5% for virtually all foods as is indicated by the 5% line in Figure 1. Neglecting the loss factor, an approximate equation for the fraction of microwave power reflected from an infinite slab food surface is given by ... 

Methods. All experiments were performed at 25°C. Critical micelle concentrations were determined using the maximum bubble pressure method on a SensaDyne 6000 surface tensiometer. Dry nitrogen was used as the gas source for the process and was bubbled through the solution at a rate of 1 bubble/sec. Cmc s measured using the Wilhemy plate method were in agreement with those obtained from the bubble tensiometer however, the bubble pressure method was used since it is less susceptible to error due to impurities and the nitrogen environment makes pH control easier. 

Ru (001) substrate in Fig. 2.11 [18J. Each trace corresponds to a different initial silver coverage. Systems of low melting metals such as Cu, Ag and Au, adsorbed on high melting metals such as Ru and W, are very suitable for fundamental desorption studies, because, firstly, readsorption on the sample surface does not occur and, secondly, the rate of desorption is measured without any systematic error due to background pressures, as would be the case with gases such as H2, CO and N2. Metallic overlayers have recently attracted attention as models for bimetallic surfaces in reactivity studies [19,20]. We use the data of Fig. 2.11 to show that TDS gives information on ... 

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