Radiant flux intensity

Figure 9-8 shows the ignition boundaries of double-base propellants on radiative heating. As the incident radiant flux intensity If increases, the time of radiant heating for the ignition completion xig becomes shorter. As the propellant becomes opaque by the addition of carbon black, xig becomes shorter at constant If or If becomes smaller at constant Xig. The in-depth absorption is reduced and most of the radiative energy is absorbed at the ignition surface of the propellant. 

Incident radiant flux intensity, MW/m2 Figure 9-8. Radiative ignition criteria of double-base propellants with and without carbon black. 

These experimentally detected combustion modes were analytically predicted follo-v fing a nonlinear stability analysis of the set of equations governing the combustion process (essentially the energy conservation in the condensed phase with appropriate initial and boundary conditions). This nonlinear analysis accounts for the influence of the properties of the burning material and the ambient conditions (included pressure and diabaticity), allowing to predict PDL and the values of pressure and radiant flux intensity originating oscillatory combustion. Moreover, several numerical checks of the analytical predictions were performed by numerical integration of the basic set of equations under the appropriate ambient conditions. Both the numerical checks and experimental results fully confirm the validity of the analytical predictions. 

Variously called, in the literature, emittance, total hemispherical intensity, or radiant flux density. 

The sun radiates approximately as a blackbody, with an effective temperature of about 6000 K. The total solar flux is 3.9 x 10 W. Using Wien s law, it has been found that the frequency of maximum solar radiation intensity is 6.3 x 10 s (X = 0.48 /rm), which is in the visible part of the spectrum 99% of solar radiation occurs between the frequencies of 7.5 X 10 s (X = 4/um) and 2 x 10 s (X = 0.15/um) and about 50% in the visible region between 4.3 x 10 s (X = 0.7 /rm) and 7.5 X 10 s (X = 0.4 /Ltm). The intensity of this energy flux at the distance of the earth is about 1400 W m on an area normal to a beam of solar radiation. This value is called the solar constant. Due to the eccentricity of the earth s orbit as it revolves around the sun once a year, the earth is closer to the sun in January (perihelion) than in July (aphelion). This results in about a 7% difference in radiant flux at the outer limits of the atmosphere between these two times. 

Reflectance A measure of the extent to which a surface is capable of reflecting radiation, defined as the ratio of the intensity of reflected radiant flux to the intensity of the incident flux. 

Radiant energy Radiant flux or power Radiant intensity... 

Radiant intensity can be described as the amount of power (watt) heading in your direction, i.e., per steradian, from a light source. The total amount of power emitted by the source is the radiant flux (watt). If you integrate the radiant intensity over all solid angles, you get the total radiant flux. If it is weighted by the photopic response, then it is the luminous intensity and the luminous flux. 

Until now we have developed equations most directly adaptable to a particular case of spectral emission. In this case, the radiant flux, once emitted, suffers no further interactions on its way to the spectrometer. The intensity of the emitted flux is directly proportional to the probability distributions JN, Jp, JD, and JY. 

Differential quantum yield. It is considered as a dynamic characteristics of the system and is defined as the ratio of the reaction rate to the photon flux (calculated horn the radiant flux, the intensities of the rays of the UV lamp, the transmittance of the optical window of the reactor, and the absorbance of TiC>2). A quantum yield of ca. 0.1 was found in the region where r varies linearly with . 

Irradiance is the radiant flux incident on a plane, for example, a photographic emulsion coating. The term intensity is commonly used with this meaning in the photographic literature, and the symbol I has been retained in much of the literature to designate irradiance, although the I.O.S. recommends the symbol E. I is used in this chapter. 

Using these sensitivities, we can calculate the luminous flux of any light source (International Commission on Illumination 1983 Jahne 2002). Let (/,) be the radiant flux at wavelength X of the light source. Let V (X) be the sensitivity of scotopic vision and V(X) be the sensitivity of photopic vision, then the intensity of the light source is... 

Company Wavelength (nm) FWHM (nm) Radiant flux (mW (3j 20 mA) Luminous intensity (cd) Substrate... 

The Planck theory of blackbody radiation provides a first approximation to the spectral distribution, or intensity as a function of wavelength, for the sun. The black-body theory is based upon a "perfect" radiator with a uniform composition, and states that the spectral distribution of energy is a strong function of wavelength and is pro portional to the temperature (in units of absolute temperature, or Kelvin), and several fundamental constants. Spectral radiant exitance (radiant flux per unit area) is de fined as ... 

The hemispherical emissive power E is defined as the radiant flux density (W/m2) associated with emission from an element of surface area dA into a surrounding unit hemisphere whose base is copla-nar with dA. If the monochromatic intensity ( 2, X) of emission from the surface is isotropic (independent of the angle of emission, 2), Eq. (5-101) may be integrated over the 2k sr of the surrounding unit hemisphere to yield the simple relation Ex = nix, where >, = Ex(X) is defined as the monochromatic or spectral hemispherical emissive power. 

Intensity Traditional term for photon flux, flumes rate, irradiance or radiant power (radiant flux). In terms of an object exposed to radiation, the term should now be used only for qualitative descriptions. 

In quantitative analysis usually calibration functions are needed which reflects the relation between the measured quantity (for instance, the radiant flux) and the concentration. The S/N ratio should be as high as possible in order to afford the maximum number of distinguishable intensity intervals. As a consequence, the spectral band width should... 

A units can be of interest) to obtain good precision and a low limit of detection. Since the detector actually measures the radiant flux density (intensity) in the presence or absence of analyte, the direct readout woxUd be in transmittance (P/Po) or in percent transmission (% T = lOOP/Po) or in some early models % absorption (100 - %T). Since linear relationships are easier to handle than logarithmic relationships, %T is converted into absorbance units automatically by the instrument ... 

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