Spectral Distribution Of Radiation Research Articles

On Wien’s peaks

Most Modern Physics Books contain a chapter on the Laws of Black Body radiation when introducing the principles of Quantum Mechanics. These laws govern many phenomena that we encounter in daily life, technological developments, and scientific research. For that, this old subject is still of great importance, and even now some issues require our attention. This work addresses one of these topics. We describe why it has no sense to think that the wavelength at which Planck’s black-body spectral radiance distribution plotted as a function of the wavelength has its maximum value, must be the same that the wavelength calculated from the peak value obtained when the distribution is plotted as a function of another variable, such as the energy of the photons. We will show how the issue lies in using the correct form to calculate this wavelength from measured quantities.

Parametrical study on spectral radiation characteristics of solid fuel combustion medium for energy cascade utilization

From the perspective of cascade utilization of photo-thermal energy, this study investigated the effects of parameter variables including pressure, temperature, particle size and number density, and unburned ratio on the spectral radiation characteristics of solid fuel combustion. By coupling the radiative transfer equation with the accurate band model of gas radiation and the Mie theory of particle radiation, the radiation energy characteristics of the one-dimensional (1-D) combustion case were calculated parametrically. Results showed that temperature is the dominant factor. The spectral radiation proportion in the waveband of 0–2 μm accounts for 36.21 % at Ta = 1600 K. Increased pressure and particle number density enhance total radiation. The pressure mainly affects the wavebands of 0–2 μm and 3–4 μm, reaching saturation at 5 bar. Excessive particle number density hinders radiation transfer to the wall. Larger particle sizes increase the spectral radiation proportion of the short waveband. The increased unburned ratio also enhances radiation, but the promotion effect is limited. Optimization of combustion parameters plays a key role in regulating spectral radiation distribution and realizing cascade utilization of photo-thermal energy. This study provides guidance for the energy utilization of solid fuel combustion and the development of carbon neutrality technology.

Analysis of Infrared Spectral Radiance of O2 1.27 μm Band Based on Space-Based Limb Detection

The infrared spectral radiance of O2 is of great significance for space-based infrared detection. In this work, based on the demand for near-infrared spectral radiance of O2 limb detection, a method of spectral radiance calculation coupled with an atmospheric remote sensing model of limb detection is proposed. According to the selection criteria of fine spectral lines, the most suitable spectral lines of the O2 1.27 μm band for detection are given. Specifically, the limb infrared radiances of the O2 1.27 μm band were simulated by using the spectral line data from the spectral database, and the effects of molecular self-absorption were also considered. Furthermore, the infrared spectral radiance distribution of the O2 1.27 μm band was simulated under the influence of altitude, and finally, the detectability of the 1.27 μm band of O2 molecules was analyzed using the criteria of spectral line selection, radiance intensity, spectral separation range and temperature sensitivity. The calculation results show that the spectral radiance of the 1.27 μm band of O2 molecules first increases and then decreases with the decrease of the limb height, and the radiance reaches the peak value in the range of 40–50 km. In terms of the selection of spectral lines, the two groups of spectral lines R7R7, R7Q8 and R11R11, R11Q12 are most suitable for the limb detection and measurement of the O2 1.27 μm band.

Optical receiver characterizations and corrections for ground-based and airborne measurements of spectral actinic flux densities

Abstract. Solar actinic radiation in the ultraviolet and visible range (UV/VIS) perpetuates atmospheric photochemistry by inducing photolysis processes which form reactive radical species. Photolysis frequencies are rate constants that quantify the rates of photolysis reactions and therefore constitute important parameters for quantitative analyses. Photolysis frequencies are usually calculated from modelled or measured solar spectral actinic flux densities. Suitable measurement techniques are available, but measurement accuracy can suffer from non-ideal 2π or 4π solid-angle reception characteristics of the usually employed 2π optical receivers or receiver combinations. These imperfections, i.e. deviations from an angle-independent response, should be compensated for by corrections of the measured data. In this work, the relative angular sensitivities of four commonly used 2π quartz receivers were determined in the laboratory in a range 280–660 nm. Based on this information, the influence of the non-ideal responses on measured spectral actinic flux densities for ground-based and airborne applications was investigated for a wide range of atmospheric conditions. Spectral radiance distributions and contributions of direct, diffuse downward and diffuse upward spectral actinic flux densities were calculated with a radiative transfer model to derive the corrections. The intention was to determine the ranges of possible corrections under realistic measurement conditions and to derive simple parametrizations with reasonable uncertainties. For ground-based 2π measurements of downward spectral actinic flux densities, corrections typically range <10 % dependent on wavelength and solar zenith angle, with 2 %–8 % uncertainties covering all atmospheric conditions. Corrections for 4π airborne measurements were determined for the platforms Zeppelin NT (New Technology) and HALO (High Altitude and Long Range Research Aircraft) in altitude ranges 0.05–2 and 0.2–15 km, respectively. Total, downward and upward spectral actinic flux densities were treated separately. In addition to various atmospheric conditions, different ground albedos and small (<5∘) aircraft attitude variations were considered in the uncertainties, as well as aircraft headings with respect to the sun in the case of HALO. Corrections for total and downward spectral actinic flux densities again typically range <10 % dependent on wavelength, solar zenith angle and altitude, with 2 %–10 % uncertainties covering all atmospheric conditions for solar zenith angles below 80∘. For upward spectral actinic flux densities, corrections were more variable and significantly greater, up to about −50 % at low altitudes and low ground albedos. A parametrization for corrections and uncertainties was derived using uncorrected ratios of upward / downward spectral actinic flux densities as input, applicable independent of atmospheric conditions for a given wavelength, solar zenith angle and altitude. The use was limited to conditions with solar zenith angles <80∘ when direct sun radiation cannot strike upward- and downward-looking receivers simultaneously. Examples of research flights with the Zeppelin and HALO are discussed, as well as other approaches described in the literature.

Study of Intensive Anthropogenic Impacts of Submerged Wastewater Discharges on Marine Water Areas Using Satellite Imagery

This paper focuses on a detailed analysis of coastal waters under the conditions of the intense anthropogenic impacts of submerged wastewater discharges, using optical and radar satellite images. The features of the intense anthropogenic impacts on the coastal waters of the northern part of the Black Sea were studied, based on the processing and analysis of systematized archival satellite and sea truth data (2015–2021). Techniques based on the formation and analysis of the spatial (2-dimensional) spectra of optical and radar satellite images, normalized radar cross-section (NRCS), and the normalized spectral index are proposed. It is convincingly shown that these techniques make it possible to register and interpret the changes in the spatial structure of wind waves, as well as the changes in the optical spectral characteristics caused by submerged wastewater discharge due to the complex hydrodynamic and hydro-optical impact. A comprehensive analysis of the results of the processing of the heterogeneous satellite and sea truth data was carried out using a geographic information system. It was found that surface disturbances caused by anthropogenic impacts due to submerged wastewater discharges were detected by local “quasi-monochromatic” spectral maxima caused by the generation of short-period internal waves (wavelengths from ~30 m to ~165 m). These maxima can be registered by high-resolution optical and radar imagery. NRCS anomalies (2–4 dB contrasts), due to the surfactant films, floating jets, and turbulence related to wastewater discharge, are registered and described, as are the changes in the spectral radiance distributions in the blue and green bands of the electromagnetic spectrum.

2D GEM-based SXR imaging diagnostics for plasma radiation: Preliminary design and simulations

• Development of novel 2D X-ray imaging system for 3D tomography for plasma radiation. • Tokamak plasma tangential view, new data for toroidal phenomena observations. • Simulations of GEM internal structure. • Simulations of spatial and spectral radiation distributions for COMPASS Upgrade. • Dedicated data acquisition system for gaseous detectors. The purpose of this research is to design and construct a plasma radiation imaging system for fusion devices which is focused on soft X-ray region from about 2 to 15 keV photon energy. The proposed 2D diagnostic system, as opposed to conventional 1D systems, is expected to benefit from tangential field of view and to deliver new data for toroidal phenomena observations. This contribution relates to the introductory development of such 2D system laying out details on the overall design of the detecting unit (based on GEM technology) as well as on its acquisition module. The results cover also the expected photon flux and spectra foreseen for COMPASS-U device, as a first choice for testing and verification. Considerations on working medium and internal structure of the detecting sensor are presented including electrodes configurations and collecting electrode pattern. The preliminary establishments for data acquisition system are presented as well.

Analysis of the Spectral Sensitivity of Luxmeters and Light Sensors of Smartphones in Terms of Their Influence on the Results of Illuminance Measurements—Example Cases

The article presents spectral sensitivity curves of 22 typical luxmeters and 3 smartphones as a result of laboratory measurements. Based on the measurement data, errors in the spectral correction of the considered instruments and devices were calculated. Due to the fact that the value of the measured illuminance is influenced by the spectral characteristics of the radiation, in order to determine the spectral corrections coefficients, 10 light sources with different spectral distributions of radiation were taken into account. Spectral corrections factors were determined using two methods for all luxmeters and smartphones. This paper presents the relationship between the shape of the spectral sensitivity curves of a given luxmeter and the measured values of f′1 errors. Moreover, the limitations related to the use of spectral corrections in environmental measurements with the use of a luxmeter were demonstrated.

Weathering of plastic SODIS containers and the impact of ageing on their lifetime and disinfection efficacy

This work aims to study the ageing of plastic materials suitable for manufacturing solar water disinfection (SODIS) containers, such as PET, polymethylmethacrylate (PMMA), and polypropylene (PP) with and without UV-stabiliser. The evolution of mechanical and optical properties, and disinfection rates were studied over different weathering periods. PMMA and PP with a 1% content by weight of UV-stabiliser were shown to be excellent candidate materials for manufacturing SODIS devices, since they presented stable optical and mechanical properties, and both transmit UVB radiation. Since PMMA is a UV resistant but fragile, easily scratched material with a lifetime above one year, it should be selected for static SODIS devices, while PP with 1% of UV-stabiliser should be chosen for portable devices because of its great resistance and elasticity for up to nine months of solar exposure. Both materials were considered profitable on the basis of their lifetime/costs ratio. PET showed great mechanical properties for one year but, in contrast, suffered of a deterioration of its optical properties and disinfection rates. PP without UV-stabilisers suffered a dramatic degradation after a very short exposure of 2 months. Finally, a kinetic model that considers the radiation spectral distribution (thus, the transmittance spectra of the plastics as a function of the ageing time) is proposed to estimate the required solar exposure time to achieve water disinfection for the proposed plastic SODIS containers. A good agreement between predicted and experimental data was achieved, especially for containers manufactured with PET and both PPs (errors below 25%).

ДОСЛІДЖЕННЯ ВПЛИВУ КОРЕЛЬОВАНОЇ КОЛІРНОЇ ТЕМПЕРАТУРИ СВІТЛОДІОДНИХ ОСВІТЛЮВАЧІВ ПРИ ОРГАНІЗАЦІЇ ЯКІСНОГО ОСВІТЛЕННЯ АВТОМАГІСТРАЛЕЙ ЗА СКЛАДНИХ ПОГОДНИХ УМОВ

A investigation of the dependence of relative horizontal illumination level and brightness of the most common types of road surface in Ukraine when using LED illuminators with different spectral distribution of radiation in the presence of aerial aerosols of different optical densities (strong, moderate, weak fog and haze) is performed. Mathematical models of LED illuminators with correlated color temperature Tcc = (2200÷8400) K in the visible range of the spectrum λ = (380÷780) nm have been created. Their use together with the selected model of the spectral dependence of the scattering index β (λ) (Ferdinandоv’s model) of the atmospheric environment with the presence of aqueous aerosols, which cause a limited meteorological range of visibility MOR = (0.1÷3) km, showed a slight (1%) advantage in creation of illumination from lamps of a warm spectrum of radiation (TCC = 2200 K) in comparison with cold (Tcc = 8400 K) for cases of strong fogs with MOR = 100 m. Calculations involving the analysis of mathematical modeling of the spectral distribution of the reflection coefficients for two types of road surface (new and worn asphalt) proved that when using warm spectrum illuminators the brightness of the most common in Ukraine old asphalt pavement in the conditions of MOR = 100 m by 5% exceeds the corresponding value of the cold spectrum emitters. This difference gradually decreases as visibility is improved due to the weaker spectral dependence of β (λ) and at MV = 3 km is 4.5%. The advantage of using warm spectrum illuminators will be significantly enhanced for the case of estimating the brightness of the coverage over long distances, for example, airfield runways, which will significantly improve flight safety.

SUPREME THEORY OF EVERYTHING: Theoretical Formulation of The Spectral Density of Electromagnetic Radiation Emitted By A Nonblack Body

Hertzsprung-Russel Diagram (HRD) plots each star on a graph measuring the star’s brightness concerning its temperature (color) between 2000K and 50000 K. It registered about 90 percent of the stars in the universe, including the Sun, located in the main sequence branch of stars in HRD. HRD is an experimental diagram, and its theory could be supposed to be Planck's law. However, Planck's law itself is empirical and contradicts recorded astronomical experimental data. Modern astronomy can observe celestial bodies in space, with surface temperatures ranging from 0 Kelvin to millions of degrees. During this time either Planck's law or HRD didn't develop. In this paper, the spectral density of electromagnetic radiation of non-black bodies is described theoretically. The extracted parameters are compatible with the curve of main-sequence stars HRD, which indicates the spectral distribution of radiation. It proves the open hysteresis of the Supreme Theory of Everything led to the correct form of the spectral radiation distribution. I examine models that can be solved exactly with the tools of mathematics so that neither approximations nor computer simulations are required

Development of a special purpose LED ultraviolet lamp in a T8 flask

Fluorescent tubular ultraviolet lamps are used in medicine, industry, cosmetology, forensic science, and banking. During the development of the LED ultraviolet lamp in a T8 flask, a comparison of its lighting characteristics (power, energy flux, spectral distribution of radiation) with the parameters of special-purpose fluorescent lamps produced at industrial enterprises has been carried out. The design of the LED lamp includes a glass uviole tube with a diameter of 26 mm and a length of 322 mm (wall thickness is 1 mm, glass grade - SL97-3). For precise installation of the lamp in the irradiation facility and supplying electric power to it, plastic caps of the G13 pin type (the distance between the electrical contacts is 12.7 mm) are used. Measurements of electrical parameters, energy flux and spectral distribution of radiation have been carried out at nominal mains voltage on a Gooch &Housegophotocolorimetric measuring device. The developed LED lamp consumes seven times less electricity, has significantly longer (five times) expected service life and is a safer source of ultraviolet radiation, since it does not contain harmful vapors of mercury and its compounds. The LED ultraviolet lamp in a T8 flask can be used instead of the manufactured LUFT-10 lamps for special purposes, namely, in irradiators for carrying out technological processes (photochemical reactions, drying, curing), for attracting and disinsecting insects in traps, in photocopiers.

Performance of Light Sources for Plants under Altered Gravity Conditions in Parabolic Airplane Flights

Performances of light sources, a halogen lamp, a fluorescent lamp and light emitting diodes (LEDs), commonly used for plant culture were examined under altered gravity conditions created during parabolic airplane flights. The surface temperatures of the light sources, irradiances, photosynthetic photon flux densities (PPFDs) and spectral distributions of radiation from the light sources were measured at the gravity levels of 0.01, 1.0 and 1.8 G for 20 s each during parabolic airplane flights. As a result, the surface temperature of the halogen lamp bulb increased most rapidly and the irradiance increased most remarkably among the three light sources at 0.01 G. On the contrary, the surface temperatures and light intensities of LEDs were most stable followed by the florescent lamp with gravity change. These characteristics of LEDs would be suitable for plant experiments and plant culture in space. Keyword(s): LED, light, microgravity, wavelength

Real-time spectral radiance estimation of hemispherical clear skies with machine learned regression models

Whole sky spectral radiance distribution measurements are difficult and expensive to obtain, yet important for real-time applications of radiative transfer, building performance, physically based rendering, and photovoltaic panel alignment. This work presents a validated machine learning approach to predicting spectral radiance distributions (350–1780 nm) across the entire hemispherical sky, using regression models trained on high dynamic range (HDR) imagery and spectroradiometer measurements. First, we present and evaluate measured, engineered, and computed machine learning features used to train regression models. Next, we perform experiments comparing regular and HDR imagery, sky sample color models, and spectral resolution. Finally, we present a tool that reconstructs a spectral radiance distribution for every single point of a hemispherical clear sky image given only a photograph of the sky and its capture timestamp. We recommend this tool for building performance and spectral rendering pipelines. The spectral radiance of 81 sample points per test sky is estimated to within 7.5% RMSD overall at 1 nm resolution. Spectral radiance distributions are validated against libRadtran and spectroradiometer measurements. Our entire sky dataset and processing software is open source and freely available on our project website.

The Effect of Subsurface Structure on the Color Appearance of 3D Printed Objects

Relatively recent advancements in 3D printing include the ability to print with multiple materials and in multiple colors. Traditional 2D printers, which print to flat media, assume that the surface geometry has a negligible effect on the appearance. The International Color Consortium (ICC) builds profiles allowing for color communication among devices, including traditional 2D printers. The ICC does not currently have practices in place to build profiles for color 3D printers due, in part, to several unknown parameters affecting the appearance of 3D printed objects. One such unknown parameter is the surface structure. To test the effect of surface structure on the color appearance of 3D printed objects, 3D models were built digitally with goniochromatic effects in mind and then printed using a color 3D printer. Spectral radiance and bidirectional reflectance distribution function measurements of the 3D printed samples were taken and correlated with the results of a psychophysical experiment to test for changes in the appearance. It was found that surface structure does have a measurable, perceptible effect on the color appearance of 3D printed objects.

Interplay and specific features of radiation mechanisms of electrons and positrons in crystalline undulators

We predict peculiar changes in spectral distributions of radiation emitted by ultra-relativistic positrons and electrons in periodically bent crystals (PBCs) with variation of the bending amplitude. It is shown that the changes, being sensitive to the projectile energy, manifest themselves differently for negatively and positively charged projectiles. We demonstrate that the features observed are due to the interplay of different radiation mechanisms occurring in PBCs. The observations are important for design, practical realization and channeling experiments with PBCs as the key element of the novel light sources. The analysis presented is based on the grounds of accurate numerical simulations of the channeling process.

Radiation Spectrum of Sequence of Electrons Moving in Spiral in Medium

Integral expressions for spectral-angular and spectral distributions of the radiation power for the sequence of electrons moving in magnetic fields in isotropic transparent medium are investigated using the improved Lorentz`s self-interaction method. Special attention is given to the research of the fine structurre of the spectral distribution of the synchrotron-Cherenkov radiation of one, two, three and four point electrons moving along the spiral in medium. The effects of coherent radiation of harmonics and oscillations in spectrum of the synchrotron-Cherenkov radiation of two, three and four point electrons are established and investigated using the direct numerical method for calculation the function of spectral distributions of the radiation power.

Анализ цветовых характеристик источников света на базе светоизлучающих диодов в системах динамичного освещения

Lighting equipment manufacturers provide the following data that determine the lighting quality: the color temperature (CT), the general color rendering index and the ripple coefficient. However, for a lighting system to be designed in a professional manner, it is necessary to know such parameters as variation of the radiation spectral distribution in the course of operation, the repeatability of characteristics and the influence of environmental conditions on the light device as a whole. All these parameters and characteristics will allow the designer to take into account the specific features of the facility that has to be illuminated. New technologies and new light sources give an impetus for revising the existing lighting standards and rules. Light-emitting diodes (LEDs) are a relatively new, promising and energy-efficient light source, which has a number of unique properties: a long service life, high luminous efficiency, a high color rendering index, aesthetics, environmental friendliness, reliability, high strength and the possibility to control both spectral and integral parameters and characteristics. Owing to the compact size of LEDs, it became possible to make luminaires of various shapes and sizes, and, as a result, of different power and luminous flux. The existing values of luminous efficacy and improvement of the color LED selection (binning) method allow one to speak about the possibility to make a white light source based on color crystals. The use of LED-based light sources in dynamic lighting installations are of great interest for studying them because such light sources open the possibility of dimming the luminous flux and changing the radiation chromaticity independently of each other. Methods of making white LED modules with a variable color temperature (CT) on the basis of two-crystal luminiferous LEDs with different CT and multicrystal LEDs are considered. The accomplished analysis of the data obtained as a result of calculations made it possible to select suitable combinations of LEDs ensuring the best values of the color rendering index and CT repeatability.

Measuring and Modeling the Polarized Upwelling Radiance Distribution in Clear and Coastal Waters

The upwelling spectral radiance distribution is polarized, and this polarization varies with the optical properties of the water body. Knowledge of the polarized, upwelling, bidirectional radiance distribution function (BRDF) is important for generating consistent, long-term data records for ocean color because the satellite sensors from which the data are derived are sensitive to polarization. In addition, various studies have indicated that measurement of the polarization of the radiance leaving the ocean can used to determine particle characteristics (Tonizzo et al., 2007; Ibrahim et al., 2016; Chami et al., 2001). Models for the unpolarized BRDF (Morel et al., 2002; Lee et al., 2011) have been validated (Voss et al., 2007; Gleason et al., 2012), but variations in the polarization of the upwelling radiance due to the sun angle, viewing geometry, dissolved material, and suspended particles have not been systematically documented. In this work, we simulated the upwelling radiance distribution using a Monte Carlo-based radiative transfer code and measured it using a set of fish-eye cameras with linear polarizing filters. The results of model-data comparisons from three field experiments in clear and turbid coastal conditions showed that the degree of linear polarization (DOLP) of the upwelling light field could be determined by the model with an absolute error of ±0.05 (or 5% when the DOLP was expressed in %). This agreement was achieved even with a fixed scattering Mueller matrix, but did require in situ measurements of the other inherent optical properties, e.g., scattering coefficient, absorption coefficient, etc. This underscores the difficulty that is likely to be encountered using the particle scattering Mueller matrix (as indicated through the remote measurement of the polarized radiance) to provide a signature relating to the properties of marine particles beyond the attenuation/absorption coefficient.

Tomographic reconstruction of a jet engine exhaust plume using an infrared hyperspectral imager

Midwave infrared (MWIR) measurements of a well-characterized JetCat turbine engine were made using a Telops infrared Fourier transform spectrometer (IFTS) hyperspectral imager (HSI), which utilizes a 320 × 256 indium-antimonide (InSb) focal plane array, calibrated to give a spectral distribution of radiance for each pixel within the image. Measurements were also made using a Santa Barbara focal plane IR imager (InSb, 320 × 256 array) that reported integrated radiance values in the MWIR. These measurements were made at varying engine RPM and different nozzle orientations to determine temperature and concentrations of the flow. The different orientations allow for the determination of the degree of asymmetry in the flow in two dimensions. The spectral information from these measurements was used to determine temperature and species concentrations of carbon dioxide and water vapor produced by the combustion of the Jet-A fuel. This was done utilizing the hyperspectral tomography (HT) process, which combines multiple measurement paths and high-resolution spectral data to determine the temperatures and concentrations of CO2 and H2O throughout the volume. Corresponding local temperature and pressure readings were taken in order to corroborate the radiometric data. Solution sets on a grid of 0.15-in. spacing based on measurements made at 2 cm − 1 spectral resolution were generated for six exhaust planes throughout the exhaust flow of a 4 in . × 1 in . rectangular exhaust nozzle. The HT process generated core plume temperature values within ±35 K of measured thermocouple data for exhaust planes near the nozzle exit plane. These results show the successful application of the HT algorithms to IFTS HSI data for temperature and species concentration reconstruction.

A narrow-band k-distribution model with single mixture gas assumption for radiative flows

In the present study, the narrow-band k-distribution (NBK) model parameters for mixtures of H2O, CO2, and CO are proposed by utilizing the line-by-line (LBL) calculations with a single mixture gas assumption. For the application of the NBK model to radiative flows, a radiative transfer equation (RTE) solver based on a finite-volume method on unstructured meshes was developed. The NBK model and the RTE solver were verified by solving two benchmark problems including the spectral radiance distribution emitted from one-dimensional slabs and the radiative heat transfer in a truncated conical enclosure. It was shown that the results are accurate and physically reliable by comparing with available data. To examine the applicability of the methods to realistic multi-dimensional problems in non-isothermal and non-homogeneous conditions, radiation in an axisymmetric combustion chamber was analyzed, and then the infrared signature emitted from an aircraft exhaust plume was predicted. For modeling the plume flow involving radiative cooling, a flow-radiation coupled procedure was devised in a loosely coupled manner by adopting a Navier-Stokes flow solver based on unstructured meshes. It was shown that the predicted radiative cooling for the combustion chamber is physically more accurate than other predictions, and is as accurate as that by the LBL calculations. It was found that the infrared signature of aircraft exhaust plume can also be obtained accurately, equivalent to the LBL calculations, by using the present narrow-band approach with a much improved numerical efficiency.