Nonuniformities radiation from

The virtual test results showed that the cells with the greatest nonuniformity (A and B) had the largest heat fluxes at the bottom and considerably less heating at the top. This was caused by radiation from the flames, which were concentrated in the bottom of the furnace. Further, the peak heat fluxes that occured near the center of the tube banks were caused by the interaction of opposing burner jets, which met in the center of the furnace. The hot gases from the burner jets must turn... 

One would like to be sure that the current is due to uniform conduction, and not to defects or weak places in the films. Some of the earlier data, in our opinion, undoubtedly refer to nonuniform conduction. The Schottky law is still observed in some such cases. It is difficult to compare results from different laboratories because of the variation in conditions under which the oxide was made and the counterelectrodes applied, and because of uncertainties about contact areas, and other details. For example, the oxide will be heated by radiation from the evaporation source, and it is known that a rise of a few 10°C has an appreciable effect on Ta205 films. 

To demonstrate the usefulness of the induced-current representation, we determine, through examples, the power radiated from the fundamental mode of a weakly guiding circular fiber due to slight nonuniformities of various kinds. 

Consider a fiber with small nonuniformities distributed at random throughout the fiber with number density M per unit volume. The total power radiated from length dz of fiber is just the sum of the power radiated by each nonuniformity. If P(z) is the modal power at position z along the fiber, and M is sufficiently large, it follows that... 

In Section 22-5 we determined the attenuation of the fundamental mode on a weakly guiding, step-profile fiber due to radiation from a sinusoidal perturbation of the interface, using free-space antenna methods and correction factors. Here we consider the situation when the radiation field is well approximated by a single leaky mode, which can be realized by having an on-axis sinusoidal nonuniformity of the form of Eq. (22-14). The azimuthal symmetry ensures that only HEi leaky modes are excited. Further, the direction of radiation should coincide with the direction of the leaky-mode radiation [23]. If we represent the nonuniformity and the incident fundamental-mode fields by the induced current method, as in Section 22-5, the direction condition is satisfied by setting C = in Eq. (24-43), whence... 

The density of the atmosphere varies greatly from place to place, as does its composition and temperature. The average composition of dry air (air from which water vapor has been removed) is shown in Table 4.4. One reason for the nonuniformity of air is the effect of solar radiation, which causes different chemical reactions at different altitudes. The density of air also varies with altitude. For example, the air outside an airplane cruising at 10 km is only 25% as dense as air at sea level. 

B.5.3 Effective Dose Equivalent and Effective Dose Equivalent Rate. The absorbed dose is usually defined as the mean absorbed dose within an organ or tissue. This represents a simplification of the actual problem. Normally when an individual ingests or inhales a radionuclide or is exposed to external radiation that enters the body (gamma), the dose is not uniform throughout the whole body. The simplifying assumption is that the detriment will be the same whether the body is uniformly or nonuniformly irradiated. In an attempt to compare detriment from absorbed dose of a limited portion of the body with the detriment from total body dose, the ICRP (1977) has derived a concept of effective dose equivalent. 

A vertical laser beam has been used by Ashkin (1970) and Ashkin and Dziedzic (1971) to levitate weakly absorbing spherical particles by radiation pressure. Lateral stability results from the dominance of refracted over reflected components of the scattered light (see Table 7.1). Unequal reflection on opposite sides of the particle, which is caused by beam nonuniformity, produces a net force that drives the particle toward lower light levels this instability is countered by refraction, which produces a reaction that drives the particle toward higher light levels. The particle is thus laterally stabilized in the most intense part of the beam. Laser levitation has the disadvantage that it... 

For routine exposures of the public, ICRP recommends a total detriment per unit equivalent dose from uniform whole-body irradiation of 7.3 X 10 2 Sv 1, as shown in Table 3.2. Of this, the recommended probability coefficient for fatal cancers is 5.0 X 10 2 Sv-1, or about two-thirds of the total detriment, and the contributions from severe hereditary responses and weighted nonfatal cancers are 1.3 X 10 2 Sv-1 and 1.0 X 10 2 Sv, respectively. These probability coefficients are summarized in Table 3.3, and their use in radiation protection is discussed in the following section. As noted previously, the probability coefficient for weighted nonfatal cancers is not the same as the probability coefficient for incidence of nonfatal cancers. The probability coefficient for fatal cancers also gives the probability of a fatal cancer per unit effective dose. The effective dose was developed to describe nonuniform irradiations of the body and is discussed below. 

Potato, com, and wheat starch was irradiated with 9 X 1014 neutrons/cm2. Neutrons cause only a weak peptonizing effect in comparison with 7-rays (2 X 106 rep) (see Table VIII). In the first case, starch becomes radioactive. Radioactive nuclei in starch are mostly phosphate isotopes and only to a very minor extent 14C. The behavior of starch of all three origins in respect to both types of irradiation is nonuniform. Generally neutron radiation does not eliminate phosphoric moieties from starch and is less destructive.77... 

The main limitation of the technique is the problem of achieving radiochemical, as distinct from chemical, purification of the final labeled product. Purification of the irradiated sample is necessary to remove radiation-induced degradation products and labile tritium. Many of the degradation products are not only chemically similar to the parent compound, but also possess much higher specific activities. For complete purification it is necessary to use multistage processes, such as gas and column chromatography, countercurrent distribution, and fractional distillation. Distribution of isotope within a molecule is generally random and nonuniform however, in some circumstances useful specificity can be achieved.17... 

Pulsed electron irradiations are usually conducted with accelerators charged from 0.1 to 6.0 MeV, and pulse durations range from 3 to 60 nsec. The explosives are pressed pellets with thicknesses of about 0.2 of the electron range. If the samples are too thick, the electrons will be trapped in the material causing a nonuniform dose. Further, the resulting space charge causes dielectric breakdown. and initiation is caused by electric discharge rather than by absorbed radiation. 

Surfaces with Nonuniform Radiosity. If the radiosity across a given surface does not meet the assumption of uniformity, then the surface may be subdivided into subsurfaces, each of which approximates the condition of uniformity. In the limit, this reduces to relations in the form of integral equations. In this case, the net radiation method can be extended. Note that Eqs. 7.72 and 7.73 still apply to every position on surface k, but Eq. 7.74 must be modified to remove the assumption of uniform radiosity. The third equation for the net radiation method is the relation for incident radiation onto a particular location on surface k from all other surfaces, each of which can have a variable radiosity. The resulting relations are... 

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