Direct field

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

Three aspects of the inductive effect have to be considered the inductive effect, the inducto-electromeric or rr-inductive effect, and the direct field effect. The first of these is the one most frequently... 

Excluding the phenomenon of hyperconjugation, the only other means by which electronic effects can be transmitted within saturated molecules, or exerted by inductive substituents in aromatic molecules, is by direct electrostatic interaction, the direct field effect. In early discussions of substitution this was usually neglected for qualitative purposes since it would operate in the same direction (though it would be expected to diminish in the order ortho > meta > para) as the cr-inductive effect and assessment of the relative importance of each is difficult however, the field effect was recognised as having quantitative significance. ... 

Earlier in this book ( 7.2.1) the direct field effect was mentioned in rather general terms. The foregoing discussion brings out the fact that there are three aspects of the effect which have to be considered ... 

Ingold introduces the terms substrate field effect and reagent field effect to describe those aspects of the direct field effect numbered (z) and (3) in 9.1.2. His description of the substituent effect of the trimethylammonio group is thus given substantially in terms of the substrate field effect and the TT-inductive effect, i.e. it is an isolated molecule description. The reagent field effect is seen to be significant in nitration and to produce qualitatively the same 226... 

These nitrogen solutions are used both for direct field appHcation and as a nitrogen ingredient in fluid mixed fertilizers. 

No se deduction in Kooms. Sound from a source in an enclosed room can be divided into two parts the direct field, dominated by sound radiated direcdy from a source to a receiver without reflections and the reverberant field, dominated by sound that has been reflected many times by surfaces in the room before it reaches a receiver (5). This relationship is defined by the foUowing equation ... 

Urea—Formaldehyde and Urea-Based. In the 1970s and early 1980s, urea materials were in general use particularly for direct field retrofitting of cavity wall constmction of wood frame and masonry. However, because of formaldehyde odor and excess shrinkage under specific conditions, this ceUular plastic has limited use as an insulation. 

An aqueous electrolyte solution consists of a variety of charged and uncharged species, e.g. cations, anions, water dipoles, organic molecules, trace impurities, etc. which under equilibrium conditions are randomly oriented so that within the solution there is no net preferentially directed field. However, under the influence of a potential difference, the charge will be transported through the solution by cations and anions that migrate to... 

One plots the curve F(x) (Fig. 6-9) and the construction consists in tracing the direction field of lineal elements. We take, for instance x = xx to which corresponds the point on the curve F(x), and transfer... 

Meyers212 collected together several examples of the anomalous behavior of sulfones in which the group was close to the reaction center and interpreted these in terms of the negative direct field effect of the S02 oxygen atoms (cf. Meyers and colleagues141). 

The vector n is directed along the molecular axis and N is, in our approximation, the only vector describing the orientation of the directing field for every order L of the expansion of V. 

Two simplifications were made in (7.92) without significant loss of generality for the correlation functions of the directing field... 

Data Structures. Inspection of the unit simulation equation (Equation 7) indicates the kinds of input data required by aquatic fate codes. These data can be classified as chemical, environmental, and loading data sets. The chemical data set , which are composed of the chemical reactivity and speciation data, can be developed from laboratory investigations. The environmental data, representing the driving forces that constrain the expression of chemical properties in real systems, can be obtained from site-specific limnological field investigations or as summary data sets developed from literature surveys. Allochthonous chemical loadings can be developed as worst-case estimates, via the outputs of terrestrial models, or, when appropriate, via direct field measurement. 

Various approaches and techniques have been used for the determination of the actual thickness of LNAPL in the subsurface. These approaches essentially fall into two groups indirect empirical and direct field approaches. Both of these are further discussed in the following subsections. 

Direct Field Methods for Measuring Actual LNAPL Thickness... 

When a material is subjected to an electric field intensity greater than 107 V/cm (1000 V/micron), electrons may be emitted. At intensities greater than 108 V/cm (104 V/micron), ions may be emitted as the result of electron bombardment while at 5 x 108 V/cm direct field desorption may occur. 

It is possible in principle for effect 1 to exert an opposing effect by tending to decrease PT through destructive interference between the reflected and direct fields. However, for most materials likely to be encountered, either dielectrics or metals, the net result will be a lifetime decrease, not an increase, for small z. 

DENMEAD, O.T., SIMPSON, J.R. and FRENEY, J.R. (1977). Direct field measurement of ammonia emission after injection of anhydrous ammonia. Soil Science Society of America Journal 41, 1001-1004. 

Guthrie and Garrett. It uses equipment factors to generate separate costs for each of the "disciplines associated with the installation of equipment, such as installation labor, concrete, structural steel, and piping, to obtain direct field costs for each type of equipment, e.g., heat exchangers, towers, and reactors. 

For ROPE applications to tar sand mining, economic projections were published for capital costs and operating costs. Total capital costs were estimated at 53,336,000 and annual operating costs were estimated at 9,683,000. For the estimation of capital costs, direct field cost was estimated at 35,558,000. Other capital costs were based on percentages of that estimate. These cost estimates were based on mid-1989 dollars (D13089C, pp. 242-243). 

The greater sensitivity of the alkaline reaction to changes in substituent is readily explained in this way —the comparison of cis and trims compounds isolates not only the steric effect but also the direct field effect —but the correlation is poor with steric effects in this system. 

Hyperconjugation appears to be the dominant factor governing the diastereoselectivity of the hydrochlorination of 5-substituted 2-methyleneadamantanes 3 (Table 2)36. However, the product distribution for epoxidation suggests that the stereochemical course of electrophilic additions not mediated by carbocations is most likely regulated by direct field effects36. Note that, unlike in the previous reactions, the facial selectivity in this case reflects the preference for the nucleophilic attack on the corresponding carbocation. 

Field studies point in a similar direction field comparisons of peptide hydrolysis rates and amino acid turnover in coastal sediments showed that amino acid production could exceed uptake by a factor of approximately 8 (Pantoja and Lee, 1999). A comparison of potential enzyme activities and sedimentary amino acid and carbohydrate inventories in sediments from the Ross Sea also showed that potential hydrolysis rates on time scales of hours should in theory rapidly deplete sedimentary amino acid and carbohydrate inventories (Fabiano and Danovaro, 1998). In deep-sea sediments, Poremba (1995) also found that potential enzyme activities in theory could exceed total sedimentary carbon input by a factor of 200. Finally, Smith et al. s (1992) investigation of potential hydrolysis rates and amino acid uptake in marine snow demonstrated that the particle-associated bacteria were potentially producing amino acids far in excess of their own carbon demand. 

In the absence of direct field measurements of pesticide fluxes eminating from a sprayed forest a series of suppositions may be drawn from similar observations of losses from treated agricultural crops. The volatilization of dieldrin and heptachlor from a grass pasture was characterized by rather marked diurnal variations in vertical flux intensities of both insecticides during the initial days post application (12). The authors concluded that the volatilization ceased or was greatly reduced with decreased solar radiance. Estimated relative vapour concentrations of dieldrin rapidly declined from saturation 2 hours post application to 10% by evening. This parameter reached a maximum of 30 - 40% on day 2 and 20 - 25% on day 3. Although the saturated vapour concentration of heptachlor is approximately fifty... 

In summary, the IO + DMS reaction appears to be potentially important in iodine-ozone chemistry and in controlling the DMS behavior in the marine atmosphere. However, the role of this reaction remains to be confirmed by direct field measurements of key species such as IO and CH3I and also by further laboratory measurements on key reactions of the atmospheric iodine chemistry. 

WC is the climate factor and represents the amount of erosive wind energy present at a particular (county-level) location W L is a function of wind direction, field length, and width and is the unsheltered median travel distance of wind across a field and WV is the vegetative factor. The relationship between E and the other variables is highly nonlinear. 

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