Harder spectrum

Figure 6. Recreation of a figure from Peters, 1961 showing a sequence of cutoffs for ions with successively higher charge when classified by total energy per particle. The line shows a hypothetical second component with a harder spectrum than the lower energy component. (See text for discussion).

One of the attractive features of the fast reactor is its hard neutron spectrum. To expand this feature, a metallic fuel core is employed in the 4S. However, it is more difficult to reduce void reactivity for a core with a harder spectrum. It is very important to design the void reactivity to be negative in order to prevent a severe nuclear accident in the event of sudden loss of coolant, sudden loss of coolant flow or a large gas bubble entrainment in the core. 

Studies were done on the recriticality potential of relocated molten core of PFBR towards assessing the use of poisons embedded in the core catcher as a means of enhancing the mass of molten fiiel that can be supported without risk of criticaUty. The studies show that the traditional poisons such as boron or gadolinium are ineffective owing to the harder spectrum that prevails under the relocation condition. 

Break-even operation only requires approximately 800 kg of thorium per GWe-year added simply as ThF4. Start-up fissile requirements can be below a tonne per GWe for thermal spectrum designs or upward of 5.5 toruies in harder spectrum designs. Thorium start-up inventory varies from 50 to 200 tonnes per GWe. 

For breeder MSR versions, on-site continuous processing is typically proposed. In the early work of ORNL, as rapidly as the entire fuel salt on a 10-day cycle. In more recent proposed designs with harder spectrums, this time can be extended to several months and still allow breeding. With the thorium- U cycle, a factor that greatly complicates processing is that thorium behaves chemically very similar to the lanthanide fission products. 

Shifts to harder spectrums can cause a small positive reactivity addition... 

The rather long lifetimes of many triplet states often allow an appreciable buildup of the triplet-state population under constant illumination. Already in 1954 Craig and Ross 33) measured reliable T—T spectra on a single-beam recording spectrophotometer. The observation of new absorption bands in the visible part of the spectrum is not difficult and there is satisfactory agreement between the peak positions reported from different laboratories. The determination of triplet extinction coefficients requires additionally a knowledge of the stationary triplet concentration, which is much harder to obtain. The corresponding literature values are widely scattered. 

FIGURE 4.11 High-resolution (0.003 nm) absorption spectrum of N02 at room temperature (adapted from Harder et al., 1997). 

Dolomite is an alternative mineral that is used in some regions in place of cal-cite for certain applications. Dolomite is a calcium magnesium carbonate (CaCOj.MgCOj) and occurs widely in nature. Although generally similar to cal-cite in properties, it is shghtly harder (3.5), denser (2.85) and more acid resistant. Production is similar to that for calcite,but miUing is more costly and it tends to only be available at the coarser end of the size spectrum. 

With metal clusters it is even harder than in other fields of inorganic chemistry to substantiate theoretical results by energy measurements. Only two such measurements have come to the attention of the author — the photoelectron spectrum of [CpFe(C0)]4 370) andbond energy determinations in 03(00)9CX-compounds 187). However, a considerable number of papers deal with metal-metal bonding in, and the symmetry properties of, clusters as related to their stoichiometry and their electron count. These studies have confirmed the wide apphcability of the simple 18-electron rule in predicting metal-metal bonds and structures, but they have also led to an understanding of the limits of this rule for clusters with more than four metal atoms. 

Figures la, b show the hard X-ray and 7-ray spectra for the above model at t — 200 and 250 d as compared with the Ginga and Kvant observations at i = 200 d and the balloon borne observations (Wilson et al. 1988) at i = 250 d. The calculations clearly show that the spectrum becomes harder as the ejecta expands and the number of Compton scattering decreases. The power law spectra, E a, at 30 - 200 keV with the index a 1.3 (200 d) and 1.1 (250 d) are in reasonable agreement with observations.

As a prediction for future observations, X-ray and 7-ray spectra at t = 400 d and 600 d are shown in Figures lc, d. The spectrum will become harder as the column depth of the ejecta decreases. Comparison with the observations will inform us more detailed abundance distribution and the dumpiness of the ejecta. 

Diamond Hints, although not approaching bulk diamond, are harder than most refractory nitride and carbide thin films, which makes them attractive for tribological coatings. Transparency in the visible and infrared regions of the optical spectrum can be maintained and index-of-refraction values approaching that of bulk diamond have been measured. Electrical resistivities of diamond films have been produced within the full range of bulk diamond, and thermal conductivities equivalent to those of bulk diamond also have been achieved. As substrates for semiconductor electronic devices, diamond films can be produced by both the PACVD and IBRD techniques. 

Expressivity. Here we define expressivity as the variation of the spectrum and time evolution of a signal for musical purposes. That variation is usually considered to have two components, a deterministic component and a random component. The deterministic element of expressivity is the change in spectrum and time evolution controlled by the user during performance. For example, hitting a piano key harder makes the note louder and brighter (more high frequency content). The random component is the change from note to note that is not possible to control by the musician. Two piano notes played in succession, for example, are never identical no matter how hard the musician attempts to create duplicate notes. While the successive waveforms will always be identified as a piano note, careful examination shows that the waveform details are different from note to note, and that the differences are perceivable. 

The vibrational spectrum of H+ is even harder to interpret. Absorption increases at all frequencies in the infrared and the already broad water bands get broader, but not symmetrically. The additions to the water bands have been interpreted as the new bands of the HsO+ unit in H+ (Falk and Gigufere, 1957). The suggested frequencies are shown in Table 9. On the other hand it has been suggested that the rapid proton shifts from one oxygen to another precludes a band spectrum for that unit in water (Ackermann, 1961) and its absorption has been... 

A miscible polymer—polymer blend almost always yields a physical- property spectrum superior to the individual components, and this allows the development of a new set of products with significant savings in capital investment. Partly for this reason and partly because new and commercially viable polymers are becoming harder to come by/ the plastic industry has expended a sizeable sum towards identifying miscible high-performance polymer mixtures. Indeed, the more recent renewed experimental and theoretical programs have resulted in an increased number of known miscible blends. On the commercial scene, however, successful miscible polymer-polymer blends are still rather few and are limited to... 

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