Comparison advantages

The paper presents the results from systematic comparisons of contrast and resolution obtained with different types of radiation sources on steel thicknesses from 5 to 40 mm. These results have been taken into account with the definitions of the European standard for radiographic inspection of weldments (EN 1435) that is approved since 1997. Conclusions from practical investigations on pipe line sites, in petrochcemical plants and in nuclear power stations will be discussed as well. Furthermore, the presentation will stipulate a variety of advantages obtained from the new source in terras of coUimation and radiation protection. 

The physical properties of the Selenium also offer big advantages with respect to radiation shielding and beam collimation. Within the comparison of radiation isodose areas the required area-radius for a survey of 40pSv/h result in a shut off area that is for Selenium only half the size as for iridium. Sources of similar activity and collimators of same absorbtion value (95%) have been used to obtain values as mentioned in Table 3 below. 

Jones et al. [144,214] used direct dynamics with semiempirical electronic wave functions to study electron transfer in cyclic polyene radical cations. Semiempirical methods have the advantage that they are cheap, and so a number of trajectories can be run for up to 50 atoms. Accuracy is of course sacrificed in comparison to CASSCF techniques, but for many organic molecules semiempirical methods are known to perform adequately. 

Large stepsizes result in a strong reduction of the number of force field evaluations per unit time (see left hand side of Fig. 4). This represents the major advantage of the adaptive schemes in comparison to structure conserving methods. On the right hand side of Fig. 4 we see the number of FFTs (i.e., matrix-vector multiplication) per unit time. As expected, we observe that the Chebyshev iteration requires about double as much FFTs than the Krylov techniques. This is due to the fact that only about half of the eigenstates of the Hamiltonian are essentially occupied during the process. This effect occurs even more drastically in cases with less states occupied. 

The advantage of using topological indices is that they occupy very little memory and the search process is extremely simple, a comparison between numbers. The main disadvantage is that most of them are not unique, or as is usually said they are d enerate, i.e., for distinct structures they produce the same values. 

The Julia-Lythgoc olefination operates by addition of alkyl sulfone anions to carbonyl compounds and subsequent reductive deoxysulfonation (P. Kocienski, 1985). In comparison with the Wittig reaction, it has several advantages sulfones are often more readily available than phosphorus ylides, and it was often successful when the Wittig olefination failed. The elimination step yields exclusively or predominantly the more stable trans olefin stereoisomer. 

As in all Fourier transform methods in spectroscopy, the FTIR spectrometer benefits greatly from the multiplex, or Fellgett, advantage of detecting a broad band of radiation (a wide wavenumber range) all the time. By comparison, a spectrometer that disperses the radiation with a prism or diffraction grating detects, at any instant, only that narrow band of radiation that the orientation of the prism or grating allows to fall on the detector, as in the type of infrared spectrometer described in Section 3.6. 

Ultrasonic Microhardness. A new microhardness test using ultrasonic vibrations has been developed and offers some advantages over conventional microhardness tests that rely on physical measurement of the remaining indentation size (6). The ultrasonic method uses the DPH diamond indenter under a constant load of 7.8 N (800 gf) or less. The hardness number is derived from a comparison of the natural frequency of the diamond indenter when free or loaded. Knowledge of the modulus of elasticity of the material under test and a smooth surface finish is required. The technique is fast and direct-reading, making it useful for production testing of similarly shaped parts. 

Comparison to the Raschig Process. The economics of this peroxide process in comparison to the Raschig or hypochlorite—ketazine processes depend on the relative costs of chlorine, caustic, and hydrogen peroxide. An inexpensive source of peroxide would make this process attractive. Its energy consumption could be somewhat less, because the ketazine in the peroxide process is recovered by decantation rather than by distillation as in the hypcochlorite process. A big advantage of the peroxide process is the elimination of sodium chloride as a by-product this is important where salt discharge is an environmental concern. In addition to Elf Atochem, Mitsubishi Gas (Japan) uses a peroxide process. 

Acetylation of hydroxyl groups and esterification of carboxyl groups have been observed ia a limited number of cases but, ia geaeral, have ao preparative advantage over chemical methods. By comparison, phosphorylation has been useful ia the preparatioa of modified purine and pyrimidine mononucleotides from their corresponding nucleosides, eg, 6-thioguanosiae [85-31-4] (51) (97). 

AEROPHINE 3418A promoter is widely used ia North and South America, AustraHa, Europe, and Asia for the recovery of copper, lead, and ziac sulfide minerals (see Elotatton). Advantages ia comparison to other collectors (15) are said to be improved selectivity and recoveries ia the treatment of complex ores, higher recoveries of associated precious metals, and a stable grade—recovery relationship which is particularly important to the efficient operation of automated circuits. Additionally, AEROPHINE 3418A is stable and, unlike xanthates (qv), does not form hazardous decomposition products such as carbon disulfide. It is also available blended with other collectors to enhance performance characteristics. 

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