Monochromatic Brightness Research Articles

Estimation of the lifetime of solar cells in real conditions using accelerated aging under the influence of neutron and gamma radiation

In the paper, in a long-term test procedure, monocrystalline silicon cells were subjected to examination. Cells were tested in well-controlled laboratory conditions and real conditions. In laboratory conditions, white light of the artificial sun and monochromatic brightness of yellow sodium lamps were used. The testing was aimed at achieving the same aging regime in the laboratory conditions as in real conditions. This would allow for the laboratory aging algorithm of solar cells as in real conditions, to be defined, hence their working life of commercial exploitation in urban areas to be determined. By complex mathematical methods, i. e. using the theory of time duration, it was found that laboratory exposing solar cells to thermal neutrons causes their aging with the same mechanism as in real conditions.

Monochromatic brightness factors of Jupiter and Saturn

The monochromatic brightness factors for morphologically nonuniform cloudy surface fields of Jupiter and Saturn in the visible wavelength range were calculated. In the spectra of both giant planets, the combination (Raman) light scattering feature (a pseudoemission peak) was detected in the range of a strong Fraunhofer line H Ca II; and its intensity was estimated.

Rapid variability of the line He I λ 587.6 nm in the spectrum of the Herbig Ae/Be star WW Vul

We investigate the behavior of the relatively strong absorption line He I λ 587.6 nm in the spectrum of the rapid irregular variable star WW Vul (Sp A3) with the Algol-like brightness fadings. As many as 76 spectra of this star were acquired with the 2.6-m ZTSh telescope of the Crimean Astrophysical Observatory with the use of the medium-dispersion spectrograph SPEM. We show that the equivalent width of the He I line exhibits not only daily variations but also rapid oscillations with a typical period of several tens of minutes. Quasi-simultaneous observations of several standard stars with known energy distributions allowed us to calculate the monochromatic magnitudes of the variable at λ = 550 nm. There was no correlation between the equivalent widths of the line He I λ 587.6 nm and the monochromatic brightness of the star. At times we could identify the short-wave emission component of the He I line. We used the Hβ profiles to confirm the spectral type A2–A3 of WW Vul.

Radiance and color of the sky at twilight: Perturbations caused by stratospheric haze

Layers of stratospheric aerosol with optical thicknesses as small as 10−4 cause noticeable perturbations in the monochromatic logarithmic brightness gradient,G, and the color ratio,C, of the twilight sky. Modeling of the twilight's radiant properties shows that definite single-valued relationships exist between maxima inC or minima inG and optical thickness, τ, physical thickness Δh, and mean altitude,\(\overline h \), of stratospheric layers. It is therefore possible to determine τ, Δh and\(\overline h \) and monitor their variations by performing either single wavelength measurements ofG or two-wavelength spectrophotometric measurements ofC. The presence of haze in the lower troposphere and the occurrence of multiple scattering both have relatively minor influences on the recovery of the stratospheric dust properties, provided that 10<\(\overline h \)<30 km.

Optimum probabilistic processing in colour perception. II. Colour vision as template matching

A statistical approach to account for psychophysical phenomena in human colour vision is presented. The central visual processor is viewed as an optimum recognizer of stochastic patterns supplied by the periphery. The processor makes an optimum estimate of the spectral parameters of the stimulus, given the wavelength filter characteristics of the periphery, the stochastic nature of the information and an internal template to which the external stimulus is matched. The estimate is constrained in ways inferred from empirical phenomena. Subjective brightness of monochromatic stimuli and related constant brightness manifolds in the colour space constitute the constraint for brightness estimation. Results analogous and in accord with those of earlier line element theories are obtained. The Bezold-Brücke hue shift constitutes the basic constraint for hue estimation. The hue estimate involves interrelation between the fields in the experiment. Similarities and differences both in basic conceptions and results introduced by the template matching notions are discussed.

Dust release and mantle development in comets

view Abstract Citations (128) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Dust release and mantle development in comets Brin, G. D. ; Mendis, D. A. Abstract A model of dust release and dust mantle development by cometary nuclei is developed to explain the brightness asymmetry observed in comets before and after perihelion. Assuming that the cometary nucleus consists of a uniform mixture of dust and volatile ices and taking into account the differential mass spectrum of the dust and the effect of nuclear gravity, it is shown that the factor which determines whether a comet will be brighter before or after perihelion is the mass ratio of dust to volatiles in the nucleus. If this ratio is greater than about two, the comet will be brighter on the inward path and not lose its mantle near perihelion. Applying the model to comet Halley (dust to volatiles ratio presumed to be less than two), it is predicted that the comet remains without a mantle until it reaches a heliocentric distance of 2.035 AU after perihelion and loses its mantle suddenly at a distance of about 1.45 AU on the inward path, causing it to be brighter after perihelion. Predictions of monochromatic brightness are found to be in fair agreement with total observed brightnesses. Publication: The Astrophysical Journal Pub Date: April 1979 DOI: 10.1086/156966 Bibcode: 1979ApJ...229..402B Keywords: Comet Nuclei; Ice Nuclei; Interplanetary Dust; Interplanetary Medium; Mass Distribution; Brightness; Mass Ratios; Perihelions; Size Determination; DUST; MANTLE; COMETS; OBSERVATIONS; NUCLEI; ICE; BRIGHTNESS; MODELS; HALLEY; COMET; MASS; PERIHELION; ASYMMETRY; WATER; KOHOUTEK; MATHEMATICAL MODELS; Astrophysics; Comets full text sources ADS |

Emissions from the head of Comet Bradfield (1978c)

The flux distribution in the head of Comet Bradfield (1978c) during the pre-perihelion period has been obtained in the wavelength range 400–640 nm. The emission fluxes at 474 nm, 516 nm, 564 nm and 589 nm are reported. By use of the observed monochromatic brightness of the Swan band sequences, the number of C2 molecules in the head of the comet are estimated.

On the monochromatic brightness variations of comets

A calculation of the non-steady development of a multi-species atmosphere of a comet moving in a near-parabolic heliocentric orbit is presented. The monochromatic brightness variations of the characteristic cometary emission bands due to OH, CN and C2 are then evaluated assuming that the ‘parent molecules’ of these chemically unstable species are respectively H2O, HCN and H2C2 present in a homogeneous H2O clathrate nucleus. For small heliocentric distances where a quasi-steady approximation is valid, the brightness variations follow Levin's (1943) law, provided all the destruction mechanisms of the cometary molecules vary as the inverse square of the heliocentric distance. On the other hand, at large heliocentric distances Levin's law breaks down, essentially due to the large time-scales of residence of the emitting species in the cometary atmosphere. This large residence time at large heliocentric distance also produces an asymmetry between the brightness profiles of the inbound and outbound passages, such that the brightness declines less steeply with distance on the outbound passage than on the inbound. Consequently, the monochromatic brightness of OH at 4 AU outbound is about twice as large as the corresponding value inbound. While some comets show such an effect, others show just the opposite effect. These deviations, which show the limitations of our simple homogeneous model, are discussed qualitatively in terms of the plausible time varying physical structure of the cometary nucleus. The variations of the relative monochromatic brightnesses of the various emissions are also discussed, and the need for extending monochromatic brightness measurements to larger heliocentric distances is stressed.

Monochromatic brightness variations of comets

A class of comets, of which Comet Kohoutek (1973f) is typical, show total as well as monochromatic brightness asymmetries about perihelion. They are fainter after perihelion than before at the same heliocentric distance. A model of the cometary nucleus consisting of a growing non-volatile dust mantle surrounding a volatile icy core is used to discuss this phenomenon.

Apparent diameters of 172 B5V-A5V stars of the Catalogue of Geneva Observatory

The spectrophotometric method for computing the apparent stellar diameters, proposed by Chalonge and Divan (1950) and modified by Fracassini and Pasinetti (1967) was applied to 172 B5V-A5V stars (single and belonging to galactic clusters) of the Catalogue of Geneva Observatory (Rufener, 1971). In the straight line diagrams log alpha '' vs m/sub v/, drawn for the stars of the same spectral type, it is possible to identify some peculiar stars (with peculiarities in the diameter or monochromatic brightness). The agreement with the vaiues of the apparent diameters of alpha Leo, BETA Ori, alpha Lyr and alpha CMa, obtained by Hanbury Brown et al. (1967), is very good. The comparison with the diagrams s/sub v/, vs (B-V)/sub o/, R vs (B-V)/sub o/ deduce d by Wesselink (1969), seems satisfactory. The comparison with the results obtained by other authors and the grent number of stars which will be observed in the photometric system in seven colors of Geneva, demonstrate the wide possibilities of this spectrophotometric method for determining the apparent stellar diameters. (auth)

Results of spectral observations of CH Cygni for 1967?1969

Our observations permit certain conclusions concerning the changes that occurred in the spectrum of CH Cyg during the observation period. It was found that, in conformity with the results of [14], the relative monochromatic brightness and continuous radiation in the violet vary in general as a function of the variation of emission in Hβ (Figs. 6 and 5; the graph of the variation of emission in Hβ is given only in Fig. 6). But continuous radiation in the violet decreases slowly with fluctuations and does not disappear with the end of the outburst. The curves of the relative monochromatic brightness in different light change differently (Fig. 6). As regards the excesses of continuous radiation in red, green, and blue (Figs. 3–5), we attributed their presence in the spectrum partially to the effect of the red component of CH Cyg. This follows from the fact that these excesses were observed before the outburst, and during the outburst the green and blue excesses decreased in general. In addition, the red excess does not duplicate exactly the variations of hydrogen emission. This is also noted in [16], where it is shown that the variation in V is greater than in r, whereas the contribution of the Balmer and Paschen hydrogen emission to V is less than to r. Therefore, part of the red and violet excesses should be attributed to the effect of the red component.

A study of a high-pressure thermal argon plasma as a high-radiance standard

This work represents a first step in the realization of a plasma source emitting blackbody radiation. A theoretical evaluation of the conditions to be fulfilled in order to obtain strictly planckian radiation from a pure argon plasma has been made. The plasma generator is a wall-stabilized arc 49 mm in length, burning stably under pressure as high as 50 atm. Spectroscopic diagnostics of the plasma have been performed by using various methods and using the hypothesis that L.T.E. obtains. For a constant value of the electrical intensity (150 A), the electronic temperature decreases from about 14,000°K at atmospheric pressure to about 11,500°K at 50 atm. The continuous radiation has been measured between 1 and 50 atm; the values of the monochromatic brightness temperature were deduced from it and compared with the value of the electronic temperature. For the maximum values of pressure, length, and temperature, the emitted radiation is not Planckian but the brightness temperature T L of the continuum remains constant in a wide spectral range (3500 ⩽ γ[ A] ⩽ 6500). In addition, discrepancies also appear between the theoretical forecasts and the experimental values. However, the arc which has been realized can constitute a useful reference source of high radiance in the visible and near u.v. range, because of its time stability and of the reproducibility of the emitted light intensities.

Visual Observations and Spectral Investigations of the Earth’s Atmosphere Twilight Aureole from the Soyuz-5 Spacecraft

Results are given of the spectrophotometric measurements of the earth's atmosphere twilight aureole as first performed from the Soyuz-5 spacecraft. The analysis is made of the experimental findings depending on the wavelength, the perigee height of the sight ray above the earth's surface, the sunset angle, etc.. The comparison is carried out of the vertical profiles for the twilight aureole monochromatic brightness with the results of the corresponding theoretical calculations for the aerosol Elterman model (1968). The color diagram and pictures of the twilight aureole are built using theoretical values of the brightness aureole for different terrestrial atmospheric models and employing the experimental data and the results of visual observations from the Soyuz-5 spacecraft.

On the use of laser light sources in schlieren-interferometer systems

In the recording of refractive index fields, the exceedingly high monochromatic brightness of laser light sources opens up new possibilities where applications to very fast or highly self-luminous phenomena are concerned. The properties of laser light, however, pose special problems, as well as presenting special opportunities. These are examined in relation to schlieren recording, deflexion mapping, shadowgraphy and interferometry. The ultimate aim is the development of a ‘versatile' optical system which is capable of fulfilling all these functions with only minor readjustments in its optical components. This is achieved, for laser light, without either the expensive apparatus, or the considerable intensity losses with which such systems are otherwise associated.

Monochromatic brightness functions: A preliminary investigation

Monochromatic brightness functions: A preliminary investigation