Spectral Distribution Of Radiation Research Articles

A simple algorithm for the estimation of the spectral radiation distribution on a horizontal surface, based on global radiation measurements

A simple algorithm is presented for the evaluation of the spectral distribution of the solar radiation on a horizontal surface as a function of the measured total solar irradiance (global radiation). The method, valid for industrial applications (agriculture, aging of materials, etc.), is based on a triangular representation of the spectrum. Straight line algorithms between 300 and 465 nm and 465 and 900 nm are used, which are functions of the global radiation and mean adjustment coefficients. Our method has been tested on a complete year of spectral observations at eight wavelengths, as well as on typical spectral distributions for clear and overcast skies.

Radiometric and Geometric Calibration of a Visible Spectral Electro-Optic “Fisheye” Camera Radiance Distribution System

Camera systems which measure a complete hemispherical field (“fisheye” lens systems), can be applied to the measurement of the radiance, but accurate radiometric and geometric calibrations are required to obtain absolute radiance data. The calibration procedure applied to an instrument built for spectral and geometrical radiance distribution measurements in the visible wavelength region (450–650 nm), based on an electro-optic fisheye camera system, is described and validated through comparison with a mere standard radiometer.

Radiation spectrum of a sinusoidal undulator

The spectral radiation distribution is investigated for an electron moving along a sinusoid. It is shown that the radiation maximum is always at the first harmonic and no changes in the electron parameters will result in shifting the maximum to higher harmonics.

Electra-Optic Camera System For Measurement Of The Underwater Radiance Distribution

A new instrument for measuring the underwater spectral radiance distribution is described. This instrument, the electro-optic radiance distribu-tion camera system (RADS), is based on two electro-optic charge-injection device cameras with fisheye lenses and a filter changer for selection of the spectral region of interest. RADS allows a complete spectral radiance distribution to be measured in a short period of time and allows routine reduction to absolute radiometric data. Many other apparent optical properties such as vector irradiance, scalar irradiance, average cosine, and net irradiance can be derived from these radiance data. In this paper, the instrument is described, values of other optical properties derived from the data are presented, and the inherent optical property of absorption is calculated from the radiance distributions using Gershun's law.

Geometrical and spectral distribution of sky radiance: Comparison between simulations and field measurements

Spectral sky radiances computed through a simple model, based on an approximate solution of the radiative transfer equation for a plane parallel, homogeneous, cloudless atmosphere bounded by a lambertian surface, are compared with high angular resolution measurements taken with an electrooptic spectral Radiance Distribution Camera System. Elements of the model, field measurements and results of the comparison between theoretical and experimental data, are given and discussed.

The Noise of the GaAlAs Super-LED Radiation

The noise is studied of the radiation emitted by GaAlAs super-LEDs. At frequencies higher than 1 kHz only the shot noise is observed in the super-LED radiation, its spectral density being close to the theoretical value. At lower frequencies (about 100 Hz) the radiation noise spectral density Su is of the 1/f type and varies as the square of the diode current, while at still lower frequencies Su ∼ Im holds, where m > 2. As a source of the observed noise parasitic laser oscillations are proposed which is confirmed by the shape of the spectral distribution of radiation. [Russian Text Ignored].

Comparison of Water-Cooled and Air-Cooled High Pressure Sodium Lamps for Lettuce Production

ABSTRACT LETTUCE (Lactuca sativa Salina) was grown in four test chambers simulating plant factories. Two were each lighted with a 1000 W water-jacketed high pressure sodium (HPS) lamp and the other two with a similar, but conventional, air-cooled HPS lamp. The voltages to the lamps were adjusted so the modules had equal photosynthetic photon flux density (PPFD) levels. Six runs were made at different air temperatures and total number of lighted hours. Leaf temperature, tipburn, and fresh weight of the full grown plants were compared. The spectral distribution of radiation from the two types of lamps were similar in the photosynthetically active radiation (PAR) wavelength region but the water-cooled lamps produced substantially less radiation in the near infrared (IR) and thermal IR regions. This resulted in an average 0.9 C lower leaf temperature under the water-cooled lamp compared to the air cooled-lamp. Further, this difference was found not to be a function of pretreatment. At low air temperature (19.1 to 19.6 C) the water-cooled treatment plants had significantly less mass than the air-cooled plants. At moderate (22.5 C) and high air temperatures (24.6 C), there was no significant differences in plant mass between lamp treatments. The only conditions for which there was a significant difference in tipburn between lamp treatments was for the low air temperature and the high number of lighted hours. Under those conditions the tipburn levels were significantly lower for the water-cooled treatment. The water jacket captured about 500 W of energy but required an extra 8% electric power to restore its photosynthetic photon flux to that of an air-cooled lamp, giving a cooling coefficient of performance of 6.2. This compares with a coefficient of performance of 3.5 for a mechanical air conditioning system. These results demonstrate that the water-cooled lamp system has only a small potential to decrease tipburn, but in a situation where closed-cycle building cooling is required, it has the potential to substantially reduce energy consumption compared to an air-cooled lamp system with mechanical air conditioning.

Quantum beats and superradiant effects in the spontaneous emission from two nonidentical atoms

The problem considered is that of the spontaneous emission from two nonidentical two-level atoms coupled to a continuum of quantized electromagnetic modes. The atoms are separated by distances comparable to the resonant wavelength and have different transition frequencies and natural linewidths. Correlation functions and radiation rates are expressed in terms of expectation values of time-dependent atomic operators. The radiation pattern, total radiation rate and spectral distribution of radiation are obtained with the initial conditions that only one atom is excited and that the system is fully inverted. We find that the radiation pattern and total radiation rate show quantum beats when initially only one atom is excited. Moreover, the total radiation rate for strong interatomic interaction becomes greater than its initial value at the beginning of the emission process. This “superradiant” property is absent for two identical atoms. For initially fully inverted system, the radiation pattern and total radiation rate decay monotonically in time. Some weak beats can appear for drastically different atoms. The spectrum of radiation calculated for the case of strong interatomic interaction, i.e., for separations much smaller than the resonant wavelength shows two peaks, located at frequency ±Ω 12 , contrary to the case of identical atoms, when the spectrum consists of only one peak located at the frequency +Ω 12 .

The Spectral Distribution of Radiation in Two Neotropical Rainforests

The spectral quality of radiation in the understory of two neotropical rainforests, Barro Colorado Island in Panama and La Selva in Costa Rica, is profoundly affected by the density of the canopy. Understory light conditions in both forests bear similar spectral characteristics. In both the greatest changes in spectral quality occur at low flux densities, as in the transition from extreme shade to small light flecks. Change in spectral quality, as assessed by the red: far-red (R:FR) ratio, the ratio of radiant energy 400-700: 300-1100 nm, and the ratio of quantum flux density 400-700:300-1100 nm, is strongly correlated with a drop in percentage of solar radiation as measurable by a quantum radiometer. Thus, by knowing the percentage of photosynthetic photon flux density (PPFD) in relation to full sunlight, it is possible to estimate the spectral quality in the forest at a particular time and microsite. KNOWLEDGE OF LIGHT CLIMATES OF tropical rainforests is a necessary background for understanding the physiological ecology of plants growing in them (Mooney et al. 1980). The slow progress in the analysis of light climates of these forests is due to their inaccessibility, to a previous lack of instrumentation suitable for field measurements, and to the heterogeneity of light conditions within forests (Anderson 1970, Idso & de Wit 1970, Reifsnyder et al. 1970, Hutchison et al. 1980). Recent studies on radiation levels in forests have concentrated on the radiation available for photosynthesis (400-700 nm). Chazdon and Fetcher (1984a) have described photosynthetic light environments at a rainforest site in Costa Rica, and Pearcy (1983) has studied the light climate in a Hawaiian forest. In these forest understories, brief sun flecks may contribute well over 50 percent of daily photosynthetic flux density. The importance of the spectral alteration of solar radiation passing through foliage to the development and ecology of plants is coming to be more widely appreciated (Smith 1982). Leaves typically transmit and reflect little radiation in the visible wavelengths (400-700 nm), and do the opposite for wavelengths beyond 750 nm (Fig. 1). Absorptance of radiation by leaves and plant canopies is a function of these two properties (absorptance = 1 reflectance transmittance). Therefore, greater canopy density or thickness should spectrally alter the incident solar radiation to a greater extent. A growing body of literature documenting the effects of altered R:FR ratios on plant development (Child et al. 1981, Smith 1982) suggests that such changes in the spectral quality of radiation may partly control development in understory plants. Developmental features that may be especially important are those of germination (Vasquez-Yanes 1980, Frankland 1981), stem extension (Morgan & Smith 1980), leaf morI Received 2 July 1985, revision accepted 24 October 1985. phology (Hebant & Lee 1984), and juvenility (Madison

LIGHT EFFECTS ON LEAF MORPHOLOGY IN WATER HYACINTH (EICHHORNIA CRASSIPES)

Water hyacinth leaves in natural populations vary from being long and thin‐petioled to being short with inflated petioles. A variety of factors has been used experimentally to alter water hyacinth leaf shape, but what controls the development of leaf morphology in the field has not been established. We measured photosynthetic photon flux density (PPFD) and spectral distribution of radiation in a natural water hyacinth population. PPFD in the center of the water hyacinth mat was reduced to 2.7% of full sunlight, and the red to far red (R:FR) ratio was reduced to 0.28. When shoot tips of plants were exposed to artificial light environments, only plants in the treatment with a R:FR ratio comparable to that in the natural population produced leaves with long, thin petioles. Shoot tips in full sun or covered with clear plastic bags or bags that reduced light quantity without greatly altering light quality produced shorter leaves with inflated petioles. We hypothesize that the altered light quality inside a mat is a major environmental control of water hyacinth leaf morphology.

Advances in Fundamental-Parameter Methods for Quantitative XRFA

The fundamental-parameter technique is an important tool for quantitative x-ray chemical analysis and is routinely applied for the quantification of bulk specimens and single layer films. A method extending it to multiple film layers has recently been introduced by Mantler and results from such applications have been reported by Huang and Parrish. In addition, fundamental-parameter methods can be employed to predict intensity ratios of fluorescent lines as well as the spectral distribution of radiation scattered by the specimen (shape of the background in the vicinity of emission, lines). This is useful for accurate quantitative analysis in the case of a poor peak-to-background ratio, where the precise determination of net intensities is difficult.

Diffraction characteristics of the x-ray radiation of ultrarelativistic particles in perfect crystals

The diffraction characteristics of resonant x-ray transition radiation of ultra-relativistic particles in perfect crystals are studied. It is shown that the intensity of the x-ray quantum near the boundary of diffraction reflection is determined by the fourth power of the thickness of a diffractionally thick sample. The maximum of the spectral distribution of the radiation with normal polarization occurs at the minimum of the spectral distribution for parallel polarization. In the collinear geometry the maximum of the spectral distribution of the radiation of ultrarelativistic particles exceeds the corresponding values of the spectral distribution of the usual resonant transition radiation without diffraction by a factor of 10/sup 4/, and its position is independent of the energy of the particle. The high monochromaticity of the radiation is noted.

Spectral characteristics of radiation of a nonrelativistic electron moving along the arc of a circle

Detailed analysis of the spectral distribution of radiation of a nonrelativistic electron moving along the arc of a circle is given.

On a possible model of the object Cyg X-3

According to the proposed model of the Cyg X-3, it should be recognized as a binary system consisting of a pulsar and an usual star. The plasma with the frozen-in field flows out from the star. The electromagnetic continuous spectrum in the range from radio to gamma radiation owes its origin to the interaction of electrons accelerated by a pulsar with the magnetic field of the stream. The influence of the inverse Compton effect on the spectral distribution of radiation has been considered by the numerical calculations of a system of kinetic equations. The calculations show remarkable agreement with the measurements, if the particle energy spectrum is expressed as dN/dE=AE −2.2. The lower limit of the accelerated particle energy equals approximately 10−2 erg. The situation of the peak of gamma-quantum radiation of very high energy in respect to the minimum in the X-ray radiation can be explained in terms of the suggested model.

A Permanent Magnet Undulator for SPEAR

A 30 period permanent magnet (SmCo5) undulator has been designed, built and tested. The period is 6.1 cm, overall length is 1.95 m, and the gap is variable from 2.7 cm to 6.0 cm. Magnetic measurements at the midplane with a 2.7 cm gap show that the field is sinusoidal with a peak value of .28 T. Construction details and magnetic measurements are presented along with the spectral distribution of radiation produced by 3.0 GeV electrons traversing the undulator.

Dependence of the radiation spectra from channeled electrons on their energy

Abstract Quantum theory of radiation from relativistic electrons in planar channeling has been developed. Analytical expressions have been obtained for the spectral distribution of radiation using a simple model for the planar potential.

Upwelled spectral radiance distribution in relation to particulate matter in sea water

Spectral analysis of water color and concurrent measurements of the relative concentration of various particulate and dissolved constituents within a broad range of water types are necessary to quantify ocean color observations and successfully relate them to various biological and physical processes that can be monitored by remote sensing. Some of the results of a Nimbus-G prelaunch cruise in connection with the Coastal Zone Color Scanner (CZCS) experiment, which was carried out in the Gulf of Mexico in October 1977, are presented and discussed. Based upon a small but diverse sample of near-surface measurements, it appears possible to estimate total suspended particulate matter (SPM) to useful accuracies by forming ratios of the spectral radiances measured at wavelengths falling near the centers of certain CZCS bands, viz., 440 nm: 550 nm and 440 nm : 520 nm. Furthermore, the analysis suggests a very high degree of covariation between SPM and phytoplankton pigments except for certain well-defined special cases.

Spectral Distribution of Radiation in the Northern Great Lakes During Winter

Measurements of global radiation in the spectral bands 285-2800, 535-2800, 630-2800 and 700-2800 nm were collected at the eastern end of Lake Superior during the period January through May. Significant differences are reported between the various spectral bands on a monthly as well as on a daily and hourly basis, due to varying degrees and types of cloudiness. Values of net and downward radiation for the same period are also provided.

Determination of Relative Biological Effectiveness (RBE) of Soft X Rays

Differences in clinical results reported with the use of iodine-125 encapsulated implants compared to those with gold-198, radon-222, and iridium-192 prompted a study of the RBE, relative to60 Co γ radiation, of X rays simulating the spectral distribution of radiation from encapsulated125 I. The parameter used for the RBE determination was the killing of surface-attached log-phase HeLa-S3 cells. The RBE was determined at dose rates varying from 15 to 130 rad/min which are about 90 to 500 times greater than those employed in therapy with interstitial ${}^{125}{\rm I} \text{implants}$ . It was found to be approximately 1.4 when measured as a ratio of $D_{0}\text{'}{\rm s}$ and 1.3 as determined on the basis of the ratio of doses for 10% survival (dose rates of 15 and 30 rad/min). The RBE values were found to be dose-rate dependent, increasing linearly from 130 to 30 rad/min and possibly leveling off below this point.

The Use of Eigenvectors of Statistical Covariance Matrices for Interpreting Satellite Sounding Radiometer Observations

Abstract A new technique is formulated for using eigenvectors of covariance matrices to retrieve atmospheric parameters from spectral radiance observations. The eigenvector method permits the use of all spectral radiances in a simultaneous solution for cloud-free infrared sounding radiances from cloud-contaminated observations as well as for the vertical profiles of temperature, moisture and cloudiness. The effects of random observation errors are minimized without suppressing the influence of any real information structure contained in the spectral radiance distribution. Also, since the method provides for the most economical representation of any variable from a number of “terms required” point of view, computer storage and computation requirements are much less than those of other methods. The eigenvector method is tested using radiance observations synthesized for the Nimbus-6 infrared and microwave sounding instruments. Although the method has been successfully applied for the routine processing of o...