Attenuation ratio

Packer and Rees [3] extended the expression derived by Murday and Cotts [7] to include the effects of a droplet size distribution, assuming a log-normal distribution. By curve fitting they were able to determine the principal parameters of such a distribution from the experimental R-values. In the presence of a distribution of sizes, the observed echo attenuation ratio R is expressed in terms of the calculated attenuation of individual droplets, R ... 

Pulsed field gradients undoubtedly represent the ultimate approach to signal suppression (Fig. 6.8d). Attenuation ratios in excess of 1000 1 are readily achieved in a single scan, meaning the suppression of the parent or H-... 

As a general rule, the attenuation decreases in shields of large volume or when there is wide opening and unusual configurations. The attenuation ratio is hence given by the following... 

Voltage Manufacturer Yokogawa Electric, model 701944, attenuation ratio 100 1, probe bandwidth DC 400 MHz, maximum input voltage 1000 Vrms. 6000-V peak... 

Contrast Ratio Cq The contrast ratio is established on the basis of the ratio of the amplitude of the unattenuated radiation to the amplitude after attenuation through a test piece. This test piece is a lead disk which is mounted in the middle of the image converter it masks approximately 10% of the surface of the image converter. 

A corresponding composite probe with the same frequency and crystal size, however, detects the test flaw much better the echo has a 12 dB higher amplitude (see Fig. 4) and in addition, the noise level is much lower, resulting in an improved signal to noise ratio. This effect is especially observed at high sound attenuation. However, in materials with low attenuation or in case of shorter sound paths the standard probe yields a comparable good signal to noise ratio. 

The transducers discussed above were designed to propagate waves in both directions normal to the direction of the fingers. It has been shown [17] that they produce a roughly collimated beam so they can be used to inspect a band of structure whose width is the transducer finger length the maximum distance away from the transducer covered by the beam is dependent on the attenuation of the wave and the signal-noise ratio, but is typically around 1-2 m in a... 

In summary, it seems that for most Diels-Alder reactions secondary orbital interactions afford a satisfactory rationalisation of the endo-exo selectivity. However, since the endo-exo ratio is determined by small differences in transition state energies, the influence of other interactions, most often steric in origin and different for each particular reaction, is likely to be felt. The compact character of the Diels-Alder activated complex (the activation volume of the retro Diels-Alder reaction is negative) will attenuate these eflfects. The ideas of Sustmann" and Mattay ° provide an attractive alternative explanation, but, at the moment, lack the proper experimental foundation. 

The attenuation of electromagnetic radiation as it passes through a sample is described quantitatively by two separate, but related terms transmittance and absorbance. Transmittance is defined as the ratio of the electromagnetic radiation s power exiting the sample, to that incident on the sample from the source, Pq, (Figure 10.20a). 

As the attenuation of the incident beam per unit path through the solution, the turbidity is larger than the Rayleigh ratio by the factor Ibrr/S, since T is obtained by integrating Rg over a spherical surface. Thus, if Eq. (10.54) is written in terms of Rg rather than r, the proportionality constant H must also be decreased by l6n/3, in which case the constant is represented by the symbol K ... 

The inductive reactance, Xl, will tend to offset the ground capacitive reactance X,j and diminish the denominator to a certain value of Xl, say, until it completely offsets the content of X. (Xl= X, ). At higher ratios, when Xl > 3 X. g, the denominator will rise more rapidly than the numerator and will tend to attenuate the Fg a as withand X, but at a slightly higher value of max (Figure 20.7, curve 3). 

A comparison of phenol acidity in DMSO versus the gas phase also shows an attenuation of substituent effects, but not nearly as much as in water. Whereas the effect of ubstituents on AG for deprotonation in aqueous solution is about one-sixth that in the gas phase, the ratio for DMSO is about one-third. This result points to hydrogen bonding of the phenolate anion by water as the major difference in the solvating properties of water and DMSO. ... 

Multiple pathways are a major concern since depostion of PIC would have occurred. Specific soil conditions determine attenuation rates of penta PIC leachate. Once penta reaches the water table, other transport and fate processes become important. Penta exists in two forms ionized and non-ionized. The ionized form is soluble in water, while the non-ionized form is not. The ratio of the two forms in water is dependent on the pH of the aquifer. In alkaline environments penta PIC tend to be more soluble and more susceptible to advective transport and biological decay. Half-lives of penta leachate in groundwater have been estimated ranging from 27 days to 58 years. 

An examination of the attenuation hy an area ratio equation will indicate that for any practical installation, the term... 

Referring to the series filter, the degree of attenuation that can he anticipated from a given area ratio may he evaluated hy the following expression ... 

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