Power, radiated

Since the energy for one photon at this wavelength is 3.6 x 10- J, then the number of photons represented by 1 lumen is approximately 4 X 10i per second, radiated or received. Thus, the luminous flux (lumens, Im) gives the power radiating from an object or the power received by an object. 

Four parameters often used to determine a fireball s thermal-radiation hazard are the mass of fuel involved and the fireball s diameter, duration, and thermal-emissive power. Radiation hazards can then be calculated from empirical relations. For detailed calculations, additional information is required, including a knowledge of the change in the fireball s diameter with time, its vertical rise, and variations in the fireball s emissive power over its lifetime. Experiments have been performed, mostly on a small scale, to investigate these parameters. The relationships obtained for each of these parameters through experimental investigation are presented in later sections of this chapter. 

EXAMPLE 2.2 Estimate the total power radiated by a surface of 0.1 crn at a temperature of2000 K, assuming that the emissivity of this surface is 0.8. 

From classical electromagnetic theory (Jackson, 1975) for an oscillating dipole, the power radiated from the dipole oscillator is given by... 

Symbols printed in boldface represent vectors the hat above a vector signifies a dimensionless unit vector, for example R = R / J r = r(t) describes the position of the charge q differentiation with respect to time is indicated by dots so that r signifies acceleration and t = t — R/c is the retarded time. Accordingly, the power radiated due to accelerated charge per unit solid angle, Q, is given by... 

To study smaller and smaller particles requires slamming atoms with more and more powerful radiation, which can only come from more and more expensive particle accelerators. Should supeTpowerful particle accelerators be built Why or why not If so, who should fund such a project Would this money be better spent on national defense Social programs ... 

Exitance power radiated in all directions per unit area of an extense light source [2,3],... 

In the last column of the table, we estimated the power radiated in each line, in units of solar luminosity, referring to a distance of 3 kpc, following Gehrz et al. (Astrophys. J. 298, L 47, 1985). These figures may be compared to the 80 Lg radiated in the 12.8 m y [Ne II] line on day 140, according to these authors. 

The total power radiated per cm2 of surface area is proportional to the fourth power of the temperature ... 

FIGURE 5.1 Energy density U(X) emitted as a function of wavelength for blackbodies at two different temperatures. The visible region (X ss 0.4-0.7/xm) is shaded near the center. The total power radiated per unit area rises dramatically as the temperature increases. The spectrum shifts to shorter wavelengths as well. 

DNP at very low magnetic fields is attractive for two reasons. First, the electron saturation frequency at low fields is in the radiofrequency range, where it is much easier to obtain high-power radiation sources, amplifiers and transmission equipment. In fact, the first experimental verifications of the Overhauser effect were conducted between 1 and 5 mT,2/85/86 likely due to the ease of constructing a suitable magnet and equipment to perform ESR saturation. The second reason for adding DNP to a low-field system is to help overcome the limited thermal polarization at low... 

Another approach to detect anomalies on the body is the use of millimeter-wave technology, which is non-ionizing low-power radiation, enabling its use with people for detecting explosives, drugs, plastics, ceramics, wood, paper, metals, and other anomalies concealed under clothing. 

Next to the generation of electric power, radiation processing is potentially the most important commercial application of nuclear energy. Radiation processes have been developed for treating food and medical supplies to inhibit growth of bacteria, viruses, fungi, and insects, and for polymerization of plastics and rubber. They take the place of thermal... 

The motional resistance, R2, represents power radiated into the contacting liquid by the oscillating device surface. It can be considered a shear-wave radiation resistance. This motional resistance leads to resonance damping. Muramatsu et al. [19] and Beck et al. [20] have shown experimentally that the motional resis-... 

In the 1930 s, vinyl monomers were found to undergo chain polymerization when subjected to gamma-rays (6) or to neutrons generated by a cyclotron (7). However, the more extensive work was carried out in the late 1940 s when it became clear that powerful radiation sources would become practical tools of interest to industry. 

Early work in this field was conducted prior to the availability of powerful radiation sources. In 1929, E. B. Newton "vulcanized" rubber sheets with cathode-rays (16). Several studies were carried out during and immediately after world war II in order to determine the damage caused by radiation to insulators and other plastic materials intended for use in radiation fields (17, 18, 19). M. Dole reported research carried out by Rose on the effect of reactor radiation on thin films of polyethylene irradiated either in air or under vacuum (20). However, worldwide interest in the radiation chemistry of polymers arose after Arthur Charlesby showed in 1952 that polyethylene was converted by irradiation into a non-soluble and non-melting cross-linked material (21). It should be emphasized, that in 1952, the only cross-linking process practiced in industry was the "vulcanization" of rubber. The fact that polyethylene, a paraffinic (and therefore by definition a chemically "inert") polymer could react under simple irradiation and become converted into a new material with improved properties looked like a "miracle" to many outsiders and even to experts in the art. More miracles were therefore expected from radiation sources which were hastily acquired by industry in the 1950 s. 

Near rich limits of hydrocarbon flames, soot is sometimes produced in the flame. The carbonaceous particles—or any other solid particles— easily can be the most powerful radiators of energy from the flame. The function k(t) is difficult to compute for soot radiation for use in equation (21) because it depends on the histories of number densities and of size distributions of the particles produced for example, an approximate formula for Ip for spherical particles of radius with number density surface emissivity 6, and surface temperature is Ip = Tl nrle ns) [50]. These parameters depend on the chemical kinetics of soot production—a complicated subject. Currently it is uncertain whether any of the tabulated flammability limits are due mainly to radiant loss (since convective and diffusive phenomena will be seen below to represent more attractive alternatives), but if any of them are, then the rich limits of sooting hydrocarbon flames almost certainly can be attributed to radiant loss from soot. 

Susceptibility of munitions to unplanned deton from effects of high-powered electromagnetic fields can be tested wi improved accuracy in one of the newest research facilities at Picatinny Arsenal, Dover, Nj. The electromagnetic hazard simulation chamber is believed unique in its capacity of creating concentrated power (radiation up to lOOOO watts) and dissipating it at the chamber s center for test purposes. The chamber is 70ft long,... 

If the most powerful radiation of a mercury lamp, 2536.5 A., were active in ozone formation, the bulk of ozone formation would have to be attributed to this one radiation and ozone formation would also be obtained after insetting the filters. Keeping in mind the behavior of these three filters towards ultraviolet light, the small amount of ozone formed on interposing the filters WG 8 and WG 10 riay be attributed to radiations below 2100 A., for which WG 8 and especially WG 10 a re slightly transparent. Using liquid oxygen and a powerful mercury lamp (440 watts) the results were similar to those just described. ... 

FIGURE 5.6 Net power radiated per unit of black surface to 77°F (298 K) surroundings. 

Not only is there a need for the characterization of raw bulk materials but also the requirement for process controled industrial production introduced new demands. This was particularly the case in the metals industry, where production of steel became dependent on the speed with which the composition of the molten steel during converter processes could be controlled. After World War 11 this task was efficiently dealt with by atomic spectrometry, where the development and knowledge gained about suitable electrical discharges for this task fostered the growth of atomic spectrometry. Indeed, arcs and sparks were soon shown to be of use for analyte ablation and excitation of solid materials. The arc thus became a standard tool for the semi-quantitative analysis of powdered samples whereas spark emission spectrometry became a decisive technique for the direct analysis of metal samples. Other reduced pressure discharges, as known from atomic physics, had been shown to be powerful radiation sources and the same developments could be observed as reliable laser sources become available. Both were found to offer special advantages particularly for materials characterization. 

The power radiated by a particle moving along a circular trajectory with radius p is given by the relation ... 

The release of radiation by radioactive isotopes—radioisotopes, for short—is called decay. The nuclei of such radioisotopes are rmstable. However, not aU ruistable nuclei decay in the same way. Some give off more powerful radiation than others or different kinds of radiation. Between 1896 and 1903, scientists had discovered three types of nuclear radiation. Each type changes the nucleus in its own way. These three types were named after the first three letters of the Greek alphabet alpha (a), beta (/3), and gamma (y). 

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