Radiation Flux Density Research Articles

Possibilities for increasing the thermal stability of the receiving mirror of a telescope by controlling the conditions of the heat transfer on its back surface

The influence of the heat transfer conditions on the back surface of a large parabolic mirror on the thermally induced shift in focus when the working surface absorbs a portion of the incident radiation was investigated. In addition, a comparison of the thermal aberration of the mirror under the conditions of natural heat transfer on the back and working surfaces when the back surface is thermally insulated or thermally stabilized was carried out. As a result of this research, it was shown that, for mirrors made of materials with low thermal conductivity, such as Zerodur or Sitall, the thermal insulation of the back surface leads to an approximate 40-fold decrease in the thermally induced focus increment, which is due to the compensation of the flexural deformation of the mirror. For a mirror made of a material with high thermal conductivity (such as silicon carbide), the thermal insulation of the back surface has the opposite effect. At the same time, the gain from the thermal stabilization of this surface is small—a factor of only 1.36. The results and conclusions presented herein are relevant for mirrors used in both ground- and space-based telescopes, operating under conditions when absorbed radiant flux density values do not exceed 50 W/m2. The proposed calculation method is convenient for determining ways to reduce the thermal aberration in mirrors.

Effect of nano silver coating on thermal protective performance of firefighter protective clothing

The main aim of this experimental work is to find out possible improvement in thermal protective performance of firefighter protective clothing when subjected to different level of radiant heat flux density. Firefighter protective clothing normally consists of three layers: outer shell, moisture barrier and thermal liner. When thermal protective performance of firefighter protective clothing is enhanced, the time of exposure against radiant heat flux is increased, which will provide extra amount of time to firefighter to carry on their work without suffering from severe skin burn injuries. In this study, the exterior side of outer shell was coated with nano-silver metallic particle through magnetron sputtering technology. Coating of outer shell with nano-silver particles was performed at three level of thickness, i.e. 1, 2 and 3 µm, respectively. All the uncoated and silver coated specimens were then characterized on air permeability tester, Permetest and radiant heat transmission machine. It was observed that coating has insignificant difference on the air and water vapor permeability of specimen and a significant decline was recorded for the value of transmitted heat flux density Qc (kW/m2) and percentage transmission factor (%TF Qo) as compared to uncoated specimen when subjected to 10 kW/m2 and 20 kW/m2 indicating improvement of thermal protective performance. These values go on further reduction with increase in thickness of coating layer of nano-silver particles.

Coupling of photocatalytic and separation processes as a contribution to mineralization of wastewater

We propose to investigate the effect of recovery rates ranging from 50 to 90% on rejection of selected Pharmaceutical actives compounds wastewater (PhACs) by nanofiltration (NF) and the further treatment of NF concentrate by photocatalysis. In agreement with the literature, our results indicate that the chemical properties and composition of the effluent depend on the volume reduction factor. Then, the study focuses on the photocatalytic degradation of the selected molecules. The efficiency of photocatalytic treatment according to incident radiant flux density and the volumetric reduction factor (VRF) have been done to evaluate the global TOC destruction and the degradation of each contaminant. The degradation of target molecules in the concentrate (VRF = 2) by photocatalysis ranged from 20% to 80%. However, for higher VRF, competition with organic matter and alkalinity effects led to low degradation yields. The study of the influence of incident radiant flux density on degradation rate confirmed results already obtained by the authors and, this time, generalizes them for a complex matrix. Results show that coupling photocatalysis with a membrane process seems to be a complementary processes to classical waste water treatment in order to oxidized persistent molecules.

Thermodynamic and optical analyses of a hybrid solar CPV/T system with high solar concentrating uniformity based on spectral beam splitting technology

A novel multi-segment mirror hybrid solar concentration photovoltaic/thermal (CPV/T) system using the spectral beam splitting technology is proposed, and its composition, working principle and structural design method are introduced in this paper. The Needle optimization method is employed to design the spectral beam splitter for the CPV/T system. The Monte Carlo Ray Tracing method is used to simulate the solar concentrating process and the results reveal that the CPV/T system can provide high uniformity of solar radiation flux density distribution on solar cells. The relationships of key structural and optical parameters of the CPV/T system are investigated. The results indicate that increasing the solar cell installation height and reducing the solar cell width can both improve the geometric concentration ratio of the CPV/T system. The sun tracking error effect analysis is carried out. The analysis results indicate that the CPV/T system has an overall optical efficiency higher than 76.3% when the sun tracking error is less than 1°. Furthermore, the thermodynamic analysis of the proposed CPV/T system is conducted and the results show that the PV conversion efficiency and overall energy efficiency of the CPV/T system are both higher than those of the CPV system under the same condition.

Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

Interpreting remotely-sensed data requires realistic, but simple, models of radiative transfer that occurs within a vegetation canopy. In this paper, an improved version of the stochastic radiative transfer model (SRTM) is proposed by assuming that all photons that have not been specularly reflected enter the leaf interior. The contribution of leaf specular reflection is considered by modifying leaf scattering phase function using Fresnel reflectance. The canopy bidirectional reflectance factor (BRF) estimated from this model is evaluated through comparisons with field-measured maize BRF. The result shows that accounting for leaf specular reflection can provide better performance than that when leaf specular reflection is neglected over a wide range of view zenith angles. The improved version of the SRTM is further adopted to investigate the influence of leaf specular reflection on the canopy radiative regime, with emphases on vertical profiles of mean radiation flux density, canopy absorptance, BRF, and normalized difference vegetation index (NDVI). It is demonstrated that accounting for leaf specular reflection can increase leaf albedo, which consequently increases canopy mean upward/downward mean radiation flux density and canopy nadir BRF and decreases canopy absorptance and canopy nadir NDVI when leaf angles are spherically distributed. The influence is greater for downward/upward radiation flux densities and canopy nadir BRF than that for canopy absorptance and NDVI. The results provide knowledge of leaf specular reflection and canopy radiative regime, and are helpful for forward reflectance simulations and backward inversions. Moreover, polarization measurements are suggested for studies of leaf specular reflection, as leaf specular reflection is closely related to the canopy polarization.

Первые результаты абсолютных измерений потока солнечного излучения на Иркутском радаре некогерентного рассеяния (ИРНР)

The Irkutsk Incoherent Scatter Radar (IISR) allows us to carry out passive radio observations of the Sun and other powerful radio sources. We describe a method for absolute measurements of spectral flux density of solar radiation at IISR. Absolute measurements are meant to determine the flux density in physical units [W·m–2·Hz–1]. The IISR antenna is a horn with frequency beam steering, therefore radio sources can be observed at different frequencies. Also there is a polarization filter in the antenna aperture, which passes only single (horizontal) polarization. To acquire flux density absolute values, the IISR receiver is calibrated by the Cygnus-A radiation. Since the Sun’s position in the IISR antenna pattern is determined by a frequency differing from the Cygnus-A observation frequency, we perform an additional calibration of the antenna overall frequency response in the 154–162 MHz operation frequency range, using the background sky noise. The solar disk size is comparable with the main beam width in the north—south direction, hence the need to take into account the shape of the brightness distribution in the operation frequency range. The average flux density of the quiet-Sun radiation was ~5 sfu (solar flux units, 10–22 W·m–2·Hz–1) at the 161 MHz frequency.

First results of absolute measurements of solar flux at the Irkutsk Incoherent Scatter Radar (IISR)

The Irkutsk Incoherent Scatter Radar (IISR) allows us to carry out passive radio observations of the Sun and other powerful radio sources. We describe a method for absolute measurements of spectral flux density of solar radiation at IISR. The absolute measurements are meant to determine the flux density in physical units [W·m–2·Hz–1]. The IISR antenna is a horn with frequency beam steering, therefore radio sources can be observed at different frequencies. Also there is a polarization filter in the antenna aperture, which passes only single (horizontal) polarization. To acquire flux density absolute values, the IISR receiver is calibrated by the Cygnus-A radiation. Since the Sun’s position in the IISR antenna pattern is determined by a frequency differing from the Cygnus-A observation frequency, we perform an additional calibration of the frequency response in the 154–162 MHz operation frequency range, using the background sky noise. The solar disk size is comparable with the main beam width in the north—south direction, hence the need to take into account the shape of the brightness distribution in the operation frequency range. The average flux density of the quiet-Sun radiation was ~5 sfu (solar flux units, 10–22 W·m–2·Hz–1) at the 161 MHz frequency.

Comparison of thermal performance of firefi ghter protective clothing at diff erent levels of radiant heat flux density

Comparison of thermal performance of firefi ghter protective clothing at diff erent levels of radiant heat flux density

Spatial Problem of the Aerophysics of a Superorbital Space Vehicle at High Altitudes

The spatial problem of the aerophysics of a superorbital entry of the Apollo-4 command module into the dense layers of the Earth’s atmosphere at an angle of attack of 25°, an entry velocity V∞ = 10.7 km s–1, and altitudes of 91.5 and 76.2 km has been solved. The distributions of the spectral and integral radiative heat flux densities along the entire streamlined surface have been derived. A significant role of the electronic bands of diatomic molecules in the radiative heating of the surface has been shown.

Far-red radiation and photosynthetic photon flux density independently regulate seedling growth but interactively regulate flowering

Shade-avoidance responses can be triggered by a decrease in the red (R, 600–700 nm) to far-red (FR, 700–800 nm) radiation ratio, by a decrease in photosynthetic photon flux density (PPFD), or both. The effects of decreased PPFD on plant responses are often confounded with the effects of reduced blue (B, 400–500 nm) photon flux density, which is another signaling factor for shade-avoidance responses. We postulated that PPFD would not influence R:FR-mediated shade-avoidance responses if B photon flux density was constant. We grew seedlings of petunia (Petunia ×hybrida), geranium (Pelargonium ×hortorum), and coleus (Solenostemon scutellariodes) under three R:FR (1:0, 2:1, and 1:1) at two PPFDs (96 and 288 μmol m–2 s–1), all with a B photon flux density of 32 μmol m–2 s–1. As R:FR decreased, stem length in all species increased. Decreasing R:FR increased individual leaf area of petunia, and shoot dry weight of petunia and coleus. Increasing PPFD decreased chlorophyll concentration and increased leaf mass per area, net CO2 assimilation, whole-plant net assimilation, and dry weight in at least two species, independent of R:FR. In petunia, a long day plant, decreasing R:FR promoted subsequent flowering at both PPFDs, but to a greater extent under the lower PPFD. In day-neutral geranium, the addition of FR had no effect on flowering, irrespective of PPFD. We conclude that with a constant B photon flux density, decreases in R:FR promote stem elongation and leaf expansion, and subsequent dry mass accumulation, independent of PPFD. However, for flowering of long-day plant petunia, the promotive effect of low R:FR is greater under lower PPFD.

Influence of Laser Radiation Power Density on the Intensity of Spectral Lines for Main Components in a Clay Laser-Induced Plasma

We have studied the intensity of the spectral lines for the main components in clay: Al I 309.4 nm, Al II 358.7 nm, Mg II 279.6 nm, Ti II 323.6 nm vs. the position of the object relative to the focus of the optical system when the samples are exposed to single laser pulses from a YAG:Nd3+ laser. We have determined the permissible ranges for positioning the object relative to the focus of the optical system (positive and negative defocusing) for which there is practically no change in the reproducibility of the intensity for the spectral lines for red and white clay samples. We show that the position of the object relative to the focus of the optical system should be within the range ΔZ ~ ±1.5 mm for optimal laser pulse energies for the analyte spectral lines. We have calculated the radiation flux density for different laser pulse energies and different distances from the focus to the object. We have shown experimentally that reducing the radiation flux density leads to a decrease in the intensity of the analyte spectral lines.

Comparative analysis of damageability produced by powerful pulsed ion/plasma streams and laser radiation on the plasma-facing W samples

Parallel use of directed plasma/fast ion streams from Dense Plasma Focus and of laser radiation (in a free running and Q-switched modes) for irradiations of targets looks perspective for tests of materials designed to withstand extreme thermal loads in the mainstream fusion reactors with inertial and magnetic plasma confinement. It is so because of a wide range of power flux densities and pulse durations generated by them. Tungsten is counted as the most appropriate material for the plasma-facing components. Main features of degradation of the surface layer of double forged tungsten were determined at different conditions of its irradiation by these streams. Chief similarities and differences in damageability obtained in the regimes are fixed – blisters, craters, porosity, microcracks, and discontinuity flaws etc. – that are peculiar characteristics for each mode of irradiation. The observed resemblances and dissimilarities that are specific for each regime of irradiation are explained with the help of numerical modelling of the treatment processes. It is shown that a so-called Integral Damage Factor may be used only in restricted ranges of parameters of an irradiation. It was found that in the regime of irradiation with the well-developed gas dynamic motion of secondary plasma the overall energy of radiation will be spent preferentially either on mass removal from the material's surface or on heating of a small amount of matter to high temperature (and consequently into its fast movement) depending on power flux density of radiation and its pulse structure.

Multi Charged Ions in Accelerators

We have presented the results of experimental studies of the characteristics of the products resulting from the expansion of plasmoids formed under laser irradiation at different wavelength: 0.69, 1.06 and 10.6µm. The radiation flux density was varied in a very wide range, which made it possible to obtain (different in intensity and energy) fluxes of charged and neutral particles. In this case, the positively charged ions have a charge from Z=1 to Z=30, which allows the use of laser plasma multi charged products in various nuclear physics experiments and super high energy accelerators [1].

Experiment study and modeling of novel mini-bubble column photocatalytic reactor with multiple micro-bubbles

The performance of a 3 mm bubble column reactor with multiple micro-bubbles and immobilized Fe3+/TiO2 photocatalyst was studied by photocatalytic degradation of MB. The bubble flow with multiple micro-bubbles was realized by a novel gas-liquid distributor, which can disperse a single bubble with diameter of 1481 μm into multiple micro-bubbles with average diameter of 432 μm. The idea of discretization was introduced to build the radiation model and obtain the distribution of radiation flux density of absorbed light. Reaction kinetics model containing UV-light and visible light in which mass transfer was included was built. Experimental data were fitted with the model and the kinetics parameters were obtained. The influences of reaction conditions show that multiple micro-bubbles play an important role in improving mass transfer coefficient (kL,MB), surface concentration ([Cs,MB/CMB]av) and reaction rate constant (kr). When the gas holdup εG increases from 0.0015 to 0.0110, the kr increases about 2.7 times. Compared with the single bubble flow, the kL,MB and kr of bubble flow with multiple micro-bubbles increase about 2 times, and the [Cs,MB/CMB]av also increases 2.25%. The quantum efficiency of visible light is much less than that of UV-light, which means that the utilization of visible light should be further improved.

Exact Relativistic Modeling of Einstein’s Field Equations for Isotropic Radiating Stars

We here investigate an exact relativistic model for an isotropic radiating star and the matching conditions required for the description of physically meaningful fluid. The interior matter fluid is shear-free spherically symmetric and undergoing radial heat flow collapsing under the influence of its own gravity. The model seems to be physically sound as it corresponds to the non-negative expressions for fluid density, isotropic pressure and radiation flux density throughout the star. The apparent luminosity as observed by the distant observer at rest at infinity is zero in remote past at the instance when the collapse begins and at the stage when collapsing configuration reaches the horizon of the black hole.

Studies of the Solar Radiations' Influence About Geomembranes Used in Ecological Landfill

Abstract The study shown in this paper presents the behavior of geomembranes used at the ecological landfills. The influences of the solar radiations has a great importance regarding the correct mounting of the geomembranes. The mathematical model developed for the determination anytime and anywhere in the world for the next values and parameters: apparent solar time, solar declination, solar altitude, solar azimuth and incidence angle, zone angle, angle of sun elevation, solar declination, solar constant, solar flux density, diffuse solar radiation, global radiation, soil albedo, total radiant flux density and relational links of these values. The results of this model was used for creations an AutoCAD subroutines useful for choosing the correct time for correct mounting anywhere of the geomembranes

Evaluation of significance of melatonin
 and some atmospheric and heliogeophysical factors for patients with acute coronary syndrome

Introduction. Changes in melatonin (MT) production affected by earth magnetic field (EMF) were documented, including but not limited to patients with cardiovascular diseases. Thus far, the connection between MT content and atmospheric and heliogeophysical factors with regard to acute coronary syndrome (ACS) patients has not been thoroughly studied and the existing data are controversial. Material and methods. The levels of MT metabolite 6-hydroxymelatonin were measured in urine at night (MTn) and day (MTd) time in 114 ACS and 26 stable angina (SA) patients on days 1-3 of hospital stay. Results. Significant inverse correlation between MTn content and EMF H and D-components (H, D) of EMF was found in ACS patients as well as direct correlation between the MTn levels and solar radiation flux density at a wavelength of 10.7 cm (F-10.7) and the number of sun spots (the Wolf number - W). Significant direct correlation was shown between EMF D-component value, Kp- and Ap- geomagnetic activity indices in ACS patients developing cardiovascular complications. For ACS patients, the risk of development of cardiovascular complications was 1,62 and 1,15 times greater at high Kp- and Ap-indices respectively. Conclusion. Direct connection between MTn level and solar activity factors was observed in ACS patients together with inverse correlation with geomagnetic activity which confirms the influence of heliogeophysical factors on MT production. The risk of developing cardiovascular complications increases at higher Kp-and Ap- indices which proves the effect of heliogeophysical factors on the clinical course of cardiovascular pathology. The MTn content was shown to decrease in winter in these patients.

Astronomical and Meteorological Conditions of a Solar System Operation

Acquisition and processing of as much solar energy for heating and electricity generation in Poland and in the world is a very important objective in the policy of alternative energy sources. The main problem with the reception of solar energy by solar collectors is vary energy supply at different times of day and year and low flux density of radiation. The term of solar radiation one mean transmission or emission of energy in the form of electromagnetic waves. The radiation emitted from the surface of the sun spreads out in all directions in space, reaches the Earth’s surface in only partly, especially the solar collectors. The most important parameters characterizing solar radiation are daily, monthly and annual sum of solar radiation. Its express the amount of solar energy which falls on a unit area at a given time. Number of hours of sunshine during the day are dependent on two key factors. The first one is the time from the sunrise to sunset, which strongly depends on the date and latitude. The second factor is the weather (clouds), influences solar radiation, radiation in touch with clouds is absorbed and dissipated. This publication shows the impact on the energy yield of the flat collector installation and astronomical conditions (angle of inclination and declination of solar), and climate. The calculations of determining the astronomical conditions of the place where the installation is located ware analyzed. The solar installation is located in Rzeszow (Poland) and the plate collector placed on the roof of building. Based on specific methodology for selected days the calculation of the elevation angle of the Sun, hourly angle, the sun azimuth and angle of incidence of the radiation on any plane were set. The results are shown in diagrams. The effect of cloud cover on the acquisition of solar energy by the collector is also shown.

ANALYSIS OF THE ENERGY POTENTIAL OF SOLAR LIGHT OF THE WESTERN REGION OF UKRAINE WITH THE ACCOUNT OF CLIMATIC CONDITIONS

An experimental facility for measuring and recording the flux density of solar radiation is designed and installed. An electrical circuit is developed and a pyranometer model is developed to measure the level of solar radiation, and it is graduated with a Soler Power Meter DT-1307 solar radiation flux meter. The time distribution of the flux density of solar energy is analyzed and the surface energy density of solar radiation is calculated for Ternopil. The influence of climatic conditions on the energy of solar radiation is determined. Analytical dependencies are obtained on the basis of comparison of the measured values of the flux density of solar radiation and the cloud cover taken from meteorological services. The energy potential of solar radiation during 2012-2015 in the western region of Ukraine is calculated, as well as the average monthly and average annual energy density of solar radiation. It is determined that the annual average density of the solar energy flux is 1045.9 kW∙h/m2, and its deviation does not exceed 5%. It is shown that the most favorable months for the use of solar energy are from March to September of each year.

Preparation of Finely Crystalline Yttrium-Aluminum Garnet in Solar Furnaces

The possibility is considered of preparing finely crystalline yttrium-aluminum garnet using high-temperature processes in solar furnaces. The effect of concentrated radiation heat flow density during treatment of a mixture of yttrium and aluminum oxides on phase composition of the melt obtained is revealed. The optimum radiation flux density for preparing specimens of finely crystalline single-phase yttrium-aluminum garnet is 8.4 MW/m2.