Radiation Flux Density Research Articles

CHARACTERISTICS OF NEUTRON FIELDS AROUND BIOLOGICAL SHIELDING OF RESEARCH NUCLEAR REACTORS IN RUSSIA

The paper presents the results of a study of the neutron field characteristics surrounding biological shielding of Russian research nuclear reactors to establish their expected behavior and enhance personnel neutron monitoring. The study covered five nuclear research reactors: IVV-2M, IRT-T, IRT-MEPhI, RBT-6, and SM-3. All reactors are pool-typed; some (RBT-6 and SM-3) have pressurized water, while others (IVV-2M, IRT-T, and IRT-MEPhI) have water under normal pressure. The neutron fields analyzed are located at the tank cover of reactors, in front of the reactor core covered with biological shielding, and in front of the horizontal experimental channel. The spectrum average neutron energy ranges from 0.01 MeV (RBT-6) to 1.0 MeV (SM-3). The fluence-to-ambient dose conversion coefficient varies from 15 pSv cm2 (RBT-6) to 260 pSv cm2 (SM-3). The spectra at the other measurement points exhibit the energy distribution characteristics of the neutron radiation flux density behind the biological shielding.

A new validated TRNSYS module for phase change material-filled multi-glazed windows

Incorporating phase change materials (PCM) into multi-glazed windows (MW) has been recognized as an effective way to regulate the indoor thermal environment and reduce the energy consumption of buildings. However, the design and calculation of PCM-filled multi-glazed windows (MW + PCM) remain challenging due to the lack of general transient simulation methods and integrated tools. To address this issue, the present study developed a dynamic coupled thermal and optical model for MW + PCM based on the enthalpy-temperature and interface energy balance methods. Then, the model was implemented in C++ and integrated into the TRNSYS software as a new module (Type 2602). In parallel, a test platform comprising two test chambers was established to evaluate the effect of PCM on the thermal and optical properties of the window and to validate the newly proposed module. It was found that compared to the traditional triple-glazed window (TW), the PCM-filled triple-glazed window (TW + PCM) effectively reduces the irradiance through the window by 34.17 % and the maximum temperature of the inner surface by approximately 5.56 °C. While the increase in external surface radiation flux density from 600 to 1200 W/m2 has a diminishing effect on the heat flux variation rate during the heat dissipation process for TW + PCM, it effectively shortens the latent heat absorption time by 0.50 h and increases the temperature difference between the inner and outer surfaces by 3.02 °C. The new module demonstrates satisfactory accuracy through experimental validation and simulation comparisons, with the maximum heat flux coefficient of variance of the root mean square error (CV(RMSE)) less than 6.35 % and 11.25 % under TW and TW + PCM configurations.

An efficient 3D tube-level flux-thermal model of external tubular receivers in solar power tower systems

Accurate and efficient radiative flux simulation and thermal analysis of liquid tubular receivers are essential for safe and stable operations of solar power tower systems. However, the complicated structure and photothermal processes on these receivers pose significant challenges for simulation. Although existing models have made great simplifications, the simulation results are still inefficient and inaccurate. To address these issues, a novel and universal 3D flux-thermal model is proposed. Firstly, a flux model is proposed via a tube-level Monte Carlo ray tracing method based on GPU parallel computing, enabling real-time and accurate radiative flux density distribution simulation for each absorber tube. Secondly, a high-resolution multi-tube thermal model is proposed, providing accurate 3D thermal analysis for each absorber tube. Through pre-factorization and highly parallelized designs, the proposed thermal model achieves a 600 times acceleration in efficiency, even with tens of millions of discrete elements. Finally, the novel flux-thermal model is validated against publicly published measured data from Solar Two, indicating a mean deviation of only 0.1% and a root mean square error of 0.006, demonstrating its high accuracy. Furthermore, the proposed flux-thermal model reveals complex and asymmetrical flux and temperature distributions on the absorber tube, in contrast to the symmetrical distributions obtained by the simplified models. Such inaccuracies in the simplified simulations may cause operational misjudgements and affect system safety potentially. Therefore, the proposed 3D tube-level flux-thermal model provides an accurate and efficient solution to radiative flux simulation and thermal analysis, enhancing the safe and stable operation of solar power tower systems.

Orbital and Spin Parts of Angular Momentum Flux Density of Monochromatic Radiation in Nonabsorbing Media with Nonlocal Nonlinear Optical Response

Orbital and Spin Parts of Angular Momentum Flux Density of Monochromatic Radiation in Nonabsorbing Media with Nonlocal Nonlinear Optical Response

Predicting multi-annual green roof net ecosystem exchange using machine learning

Green roofs are an urban mitigation strategy to increase CO2 uptake by green infrastructure. Reliable quantification of multi-year net ecosystem exchange (NEE) is essential for evaluating carbon balance, but proves challenging due to lack of long-term data and transferability of models. Machine learning can effectively predict NEE and identify non-linear patterns for spatially and temporally upscaling. For the first time, we developed Random Forest (RF) models using long-term eddy covariance (EC) data from 2015 to 2020 from an extensive green roof at Berlin-Brandenburg Airport (BER) to understand the influence of meteorological predictors on NEE prediction and transferability. A simple (M1), extended (M2) and optimized (M3) model based on different combinations of predictors were built. M3 performed best, deviating by −13 % from the observed uptake of −132.4 gC m−2 a−1 (R2 of 0.74), with M2 (R2 = 0.73) showing similar results. Key predictors were volumetric water content (VWC) and solar radiation flux densities. The models showed robust performance under pronounced environmental conditions. Drought in 2018 introduced significant uncertainties, whereas higher VWC in 2019 and 2020 led to enhanced performance. All models tended to overestimate CO2 assimilation and underestimate respiration of the green roof. M1 deviated by −58 % from observed NEE over the entire period, indicating transferability of M1 to other locations is not feasible, whereas transferability of M2 and M3 showed better potential for broader application with minimal calibration. This study highlights the importance of water-related variables and available energy and demonstrates that RF, incorporating NEE process understanding, can effectively predict NEE.

OPTIMIZATION OF MODE PROPAGATION FOR AN EMBEDIER OF OPTICALVORTEX BEAMS BASED ON A MICRO-RING RESONATOR

Light beams with orbital angular momentum have unique properties that make them valuable for research and practical applications. From revolutionizing communication technologies to enabling advanced microscopy and quantum computing possibilities, these beams continue to drive innovation and open up new frontiers in optics and photonics. In this paper, the dependence of the radiation flux density of an optical vortex beam on the geometry of the emitting structure is investigated. A micro-ring resonator with periodic structures is used as an optical vortex beam emitter structure. In our study, optimizing the width of the ring waveguide leads to an increase in the radiation flux power up to 30% for the resonant wavelength of 1563 nm. To analyze how the whispering gallery modes are distributed in the cross section of the annular waveguide, we increased the annular waveguide width from 400 nm to 500 nm. This proposed approach can be applied to radiating micro-ring resonators in various applications.

On the Effect of Focusing Conditions on the Emission Capacity of a Laser-Plasma Ion Source

The issues of the influence of geometric conditions of laser radiation focusing on the surface of the plasma-forming target of an laser-plasma ion source are considered. In particular, the presence of two ion emission maxima in the region of the laser radiation flux density exceeding 1011 W/m2 has been experimentally established. A possible interpretation of this effect is proposed.

Hydrogen in the Natural Gas Network—Relevance for Existing Fire Precautions

Power-to-gas technology can be used to convert excess power from renewable energies to hydrogen by means of water electrolysis. This hydrogen can serve as “chemical energy storage” and be converted back to electricity or fed into the natural gas grid. In the presented study, a leak in a household pipe in a single-family house with a 13 kW heating device was experimentally investigated. An admixture of up to 40% hydrogen was set up to produce a scenario of burning leakage. Due to the outflow and mixing conditions, a lifted, turbulent diffusion flame was formed. This led to an additional examination point and expanded the aim and novelty of the experimental investigation. In addition to the fire safety experimental simulation of a burning leakage, the resulting complex properties of the flame, namely the lift-off height, flame length, shape and thermal radiation, have also been investigated. The obtained results of this show clearly that, as a consequence of the hydrogen addition, the main properties of the flame, such as lifting height, flame temperature, thermal radiation and total heat flux densities along the flame, have been changed. To supplement the measurements with thermocouples, imaging methods based on the Sobel gradient were used to determine the lifting height and the flame length. In order to analyze the determined values, a probability density function was created.

Analysis of microwave heating of copper powder compacts

The influence of the native oxide films, which is essential for the understanding of the microwave heating of metal powder, is analyzed numerically based on the experimental data on temperature, dilatation and resistance of compacted copper powder samples. The indicative thickness of the oxide films, determined from the resistivity data using an effective medium approximation, is shown to decrease from ≥1 μm to below 1 nm. The effective complex dielectric permittivity and magnetic permeability of the copper powder with oxide films on the particles are calculated within the recently developed models. The dielectric permittivity exhibits a percolation behavior in the temperature range of the oxide decomposition, viz. 210–250 °C when microwave heating is carried out in nitrogen and 330–375 °C – in argon. The efficiency of absorption of the incident 30 GHz microwave radiation in a slab of powder is assessed separately for the electric and magnetic-type losses, the contribution of the latter being predominant until the percolation transition. The energy flux density of the incident microwave radiation required to sustain the prescribed heating rate is shown to increase during the microwave heating process from ∼20 W/cm2 to >1 kW/cm2 due to increasing reflection. The additional microwave energy input required for the completion of the endothermic oxide decomposition reaction is shown to be significant at the initial stage of the process (below 200 °C).

Estimating Fire Radiative Energy Density with Repeat-Pass Aerial Thermal-Infrared Imaging of Actively Progressing Wildfires

Studies on estimating cumulative fire intensity from spreading wildland fires based on fire radiative energy density (FRED) have primarily been conducted through controlled experiments. The objective of this study was to assess the potential for estimating FRED for freely-burning wildfires at landscape scales. Airborne thermal infrared image sequences collected 8 and 9 December 2017 during the Thomas Fire were used for surface temperature derivation and FRED estimation. Sensitivity of varying ambient temperatures, and a newly developed method that adjusts for ash radiances on fire radiative flux density (FRFD) and FRED estimates were tested. Pixel-level image classification was run to identify FRFD time sequences that were complete or incomplete because of cloud obscuration and provided the basis for an obscuration gap filling technique. Variations in estimated ambient temperature used to estimate FRFD had little impact on FRED estimates, while our ash adjustment led to notable differences. An exponential decay model characterized FRFD time sequences well, providing a basis for gap filling irregular sequences caused by atmospheric obscuration. FRED estimates were regressed on rate of spread (ROS) magnitudes and found to be positively and significantly correlated. FRED magnitudes were higher on 9 December when the Thomas Fire burned under higher wind speeds and lower relative humidity levels (Santa Ana weather conditions) than on 8 December.

Modelling of spacecraft apparent brightness A study on OneWeb constellation satellites

Artificial satellites orbiting around the Earth, under certain conditions, result to be visible even to the naked eye. The phenomenon of light pollution jeopardises the researching activities of the astronomical community: traces left by the objects are clear and evident and images for scientific purposes are damaged and deteriorated.The development of a mathematical model able to estimate the satellite’s brightness is required and it represents a first step to catch all the aspects of the reflection phenomenon. The brightness model (by Politecnico di Milano) will be exploited to implement a realistic simulation of the apparent magnitude evolution and it could be used to develop an archetype of new-generation spacecraft at low light-pollution impact.Starting from classical photometry theory, which provides the expressions of radiant flux density of natural spherical bodies, the global laws describing flux densities and the associated apparent magnitude are exploited to generalise the analysis. The study is finally focused on three-dimensional objects of whatever shape which can be the best representation of the spacecraft geometry. To obtain representative results of the satellite brightness, a validation process has been carried on. The observation data of OneWeb satellites have been collected by GAL Hassin astronomical observatory, settled in Isnello, near Palermo. The observations were carried out in order to map the satellites brightness at various illumination conditions, also targeting a single satellite across its different positions on the sky (i.e., during its rise, culmination and setting).A model aiming to estimate brightness of mega-constellation satellites (developed by Politecnico di Milano) has not been developed yet.

The importance of species-specific and temperature-sensitive parameterisation of A/Ci models: A case study using cotton (Gossypium hirsutum L.) and the automated 'OptiFitACi' R-package.

Leaf gas exchange measurements are an important tool for inferring a plant's photosynthetic biochemistry. In most cases, the responses of photosynthetic CO2 assimilation to variable intercellular CO2 concentrations (A/Ci response curves) are used to model the maximum (potential) rate of carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, Vcmax) and the rate of photosynthetic electron transport at a given incident photosynthetically active radiation flux density (PAR; JPAR). The standard Farquhar-von Caemmerer-Berry model is often used with default parameters of Rubisco kinetic values and mesophyll conductance to CO2 (gm) derived from tobacco that may be inapplicable across species. To study the significance of using such parameters for other species, here we measured the temperature responses of key in vitro Rubisco catalytic properties and gm in cotton (Gossypium hirsutum cv. Sicot 71) and derived Vcmax and J2000 (JPAR at 2000 µmol m-2 s-1 PAR) from cotton A/Ci curves incrementally measured at 15°C-40°C using cotton and other species-specific sets of input parameters with our new automated fitting R package 'OptiFitACi'. Notably, parameterisation by a set of tobacco parameters produced unrealistic J2000:Vcmax ratio of <1 at 25°C, two- to three-fold higher estimates of Vcmax above 15°C, up to 2.3-fold higher estimates of J2000 and more variable estimates of Vcmax and J2000, for our cotton data compared to model parameterisation with cotton-derived values. We determined that errors arise when using a gm,25 of 2.3 mol m-2 s-1 MPa-1 or less and Rubisco CO2-affinities in 21% O2 (KC 21%O2) at 25°C outside the range of 46-63 Pa to model A/Ci responses in cotton. We show how the A/Ci modelling capabilities of 'OptiFitACi' serves as a robust, user-friendly, and flexible extension of 'plantecophys' by providing simplified temperature-sensitivity and species-specificity parameterisation capabilities to reduce variability when modelling Vcmax and J2000.

СОЛНЕЧНЫЕ ЭНЕРГЕТИЧЕСКИЕ СИСТЕМЫ ДЛЯ ЧАСТНЫХ ПОТРЕБИТЕЛЕЙ

Currently, there is an increased interest in the use of combined autonomous power supply systems based on renewable energy sources in the world. Private consumers of the agro-industrial sector need both electric and thermal energy, while installations should not occupy significant land areas. (Research purpose) The research purpose is substantiating the use of photovoltaic systems of increased efficiency for operation in small installations used for private households and farms of the agro-industrial complex. (Materials and methods) Proposed to use a control system based on maximum power point tracking (MPPT) controllers and silicon elements of increased efficiency for more efficient operation of the entire power complex. (Results and discussion) It have been shown that when equipping an autonomous consumer with power plants, reliability and uninterrupted operation of power systems, as well as the necessary power characteristics, become important. It was determined that the daily operation time of such systems is limited by solar insolation and low radiation flux density. It has been established that for the uninterrupted operation of these systems, a reserve of energy or additional power sources is required, and taking into account the variability of solar activity, their conversion factor should be increased by combined generation of thermal and electrical energy. It was found that the modification of the surface of photocells with silver nanoparticles leads to an increase in power characteristics by 20 percent due to the initiation of the effect of surface plasmon resonance. (Conclusions) It was stated that installations for power supply to autonomous consumers of both the agricultural and municipal sectors based on renewable energy sources (in particular, solar installations), modeled using these methods and technologies, make it possible to effectively provide private consumers of the agro-industrial sector of the economy with thermal and electric energy, and when using combined energy conversion, reduce the occupied areas in calculated per unit of power.

The use of low-temperature plasma for disinfection of open surfaces of industrial premises

The results of research on inactivation of microorganisms on open surfaces of poultry houses using low-temperature non-equilibrium plasma are presented. AC electrospark discharge at atmospheric pressure was used as its source. Discharge types are streamer, flare. The simultaneous effect of electromagnetic fields, charged particles and chemically active compounds formed by electrospark discharge on the efficiency of pathogenic microflora inactivation for various surfaces (acrylic primer, epoxy resin, yacht varnish, concrete-graphite mixture) is considered. The material to be treated (a biological model of the bedding surface of the floor in the poultry house with the applied protective layer) is installed after the electrospark discharge chamber blown with plasmaforming gas (atmospheric air). The main affecting factors are active chemical compounds: ozone; free radicals (OH, O, O2), ultraviolet radiation in the range of 750–1600 THz, electromagnetic radiation from 50 Hz to 980 MHz, charged particles and vibrationally excited nitrogen and oxygen molecules. Characterizations of electromagnetic radiation flux density at electrospark discharge are obtained. According to the research results, the maximum effect of treatment of exposed surfaces with low-temperature non-equilibrium plasma is achieved when epoxy resin is used as a surface protection material. The number of inactivated microorganisms at exposure of 10-20 s reaches 100%. When inactivating microorganisms on exposed surfaces, it is not economically feasible to take exposure time longer than 20 s. The studies found no significant difference when using streamer or flare discharges to treat outdoor facility surfaces.

ВИБІР ТЕХНОЛОГІЧНИХ ПАРАМЕТРІВ ЛАЗЕРА ДЛЯ ОТРИМАННЯ НАНОСТРУКТУР НА ІНСТРУМЕНТАЛЬНІЙ СТАЛІ У12А

According to the improved model of the thermal interaction of laser radiation and the processing material, a study of the change in the maximum temperature at different depths of the surface layer was carried out on the example of tool steel U12A. The rate of change of the maximum temperature and temperature stress as a function of the heat flux density of laser radiation (LV) was also studied. The range of LV density was taken within q=108...1011 W/m2 for different times of its action, which corresponds to the conditions for the possible occurrence of NS. The study of the dependence of the rate of change of the maximum temperature on U12A steel on the density of the heat flow at different depths showed that during all times of its action, rates of temperature change of more than 107 K/s are realized, which indicates that, according to this criterion, the formation of NS is possible over the entire range of densities heat flow and at all investigated depths. To determine the possibility of accelerating the formation of NS, the values of temperature stresses in the zone of action on U12A were calculated at a density of 108...1011 W/m2 at different depths with an action time of t=10-4 ...10-10c. Which showed that the direct formation of NS from the action of temperature stresses is practically impossible, however, at a time of 10-5...10-4 of their values, they approach those required at a heat flux density of 1011 W/m2. In order to determine the technological parameters that ensure the production of NS, spatial dependences of the volume of NS on the heat flux density and the time of its action were constructed for the radius of the spot R=10-6 m (Fig. 8) and R=5•107 m (Fig. 9) . It was determined that obtaining NS is more realistic for the size of the spot 5•107 m, although the probability of obtaining them is also low. In fig. 10 and 11 show similar dependences for the grain size on the heat flux density and the time of its action for the spot size R=10-6 m and R=5•107 m when acting on U12A tool steel. The obtained spatial pictures allow, knowing the required grain size, to choose the technological parameters that allow them to be implemented. All this will be required during the development of the technology for obtaining strengthening nanostructured coatings on the cutting tool.

Оценка эффективности метода гиперплоскостей в задаче частичной идентификации неизвестного вещества

The problem of partial identification of a homogeneous medium of unknown chemical composition is investigated. The medium is subjected to repeated transillumination by X-ray fluxes collimated in energy and direction. According to the results of measuring the flux density of radiation entering and leaving the medium, it is necessary to establish the difference in the chemical composition of the medium from some in advance given substances. It is assumed that the measurements of radiation fluxes contain errors for which their maximum relative values are known. As a mathematical basis for the study the method of hyperplanes proposed earlier by the author is taken. The results of numerical calculations performed for problems of various dimensions and for a number of groups of specific chemical elements. Numerical estimates have been obtained for several groups of organic substances, under which any two substances will be successfully distinguished from each other by the results one single measurement experiment on transillumination. Using the hyperplane method in the identification problem for groups of organic substances showed enough high efficiency. As a result of computer calculations, it is shown that that any of the 1287 considered pairs of organic substances is well distinguishable if the total relative measurement error of the probing radiation flux does not exceed 9.726 \%. The analysis of the dependence of the mass attenuation coefficients of radiation from the atomic number for all chemical elements of the periodic system has been carried out and conclusions about the behavior of the identification accuracy with an increase in the dimension of the problem were done. A justification is given that the hyperplane method will be effective in solving the problem of identification for other groups of chemical elements and identification accuracy does not get worse as the dimension of the problem increases.

Self-consistent modeling and analysis of spatial homogeneity of pure Na and Na−Ar mixture resonance photoplasma in a gas cell for Voigt profile

A self-consistent modeling of the resonance photoplasma in pure Na and Na−Ar mixtures with spatial homogeneity of photoexcitation of the resonance levels of Na in the volume of a cylindrical gas cell has been carried out. The Voigt line shape and the collision broadening of the D1 and D2 lines of Na were considered. The main photoplasma parameters were calculated for the Na pressure PNa=0.0045−0.165 torr, the PAr/PNa=0 and 10k (k = 1, 2 and 3) values and the gas temperature of 680 K at the pumping resonance radiation flux density F = 40 W/(m2nm). It has been established that the electron density Ne and temperature Te increase non-linearly with the growth of the PNa and reach, respectively, 6.4·1018 m−3 at PNa=0.165 torr and PAr/PNa=100 and 0.28 eV for the pure Na photoplasma. Herewith, the dependence of Te on the Ar pressure PAr is non-monotonic. It is a consequence of the cooperative action of electron inelastic collisions of the first and second kinds with Na atoms and elastic collisions with Na and Ar atoms. The comparison of the obtained results for the L = 4R = 0.02 m case with those calculated for the infinite cylinder case with the same R value showed the good validity of the infinite cylinder approximation. As a result of our analysis of the quenching of the resonance levels and theoretical results from the literature, it has been established that the spatial non-homogeneity of the investigated photoplasma caused by this quenching does not exceed 20 % for the PNa≤0.1 torr and PAr/PNa=0 − 103. The obtained data can be used in studies of alkali-containing photoplasmas and to create photoelectric converters based on them.

Niepewność pomiarów średniej temperatury promieniowania za pomocą termometrów kulistych = Uncertainty of mean radiant-temperature measurements using globe thermometers

In the analysis of the human heat balance, the biggest problem is to precisely determine the amount of energy absorbed by a human organism under dynamically changing solar conditions and while being surrounded by many different surfaces that can absorb, emit or reflect solar radiation in different ways. Therefore, in thermal comfort studies some simplifications of the radiation field around human body are necessary and thus the concept of mean radiant temperature (Mrt) is most often used. Mrt values can be derived either from direct instrumental measurements or calculated by one of the microclimate models. The most accurate way to determine the Tmrt outdoors is by integral radiation measurements and the calculation of angular factors (i.e. the proportion of radiation received by the human body from different directions). This method involves simultaneous measurements of long- and short-wave radiation flux densities in six directions, which requires three sets of net radiometers. Although this method of Mrt determination describes the radiation environment accurately and independently of the variable wind field, it requires the use of expensive and complex measurement devices. Cheap and easy to operate alternative offers globe thermometer. In steady state conditions, readings from the air temperature sensor inside the globe thermometer (tg) will reflect the convective and radiative heat exchange around the globe thermometer. Knowing tg, as well as globe emissivity and diameter, the Mrt may be calculated. In this research three different globe thermometers were used to determine Mrt: 15-cm standard globe thermometer (SGT) and two 4-cm custom made acrylic globe thermometers (AGT) painted in black and grey. The measurements were conducted in the summer in Warsaw, on two selected green areas, under sunny and warm weather conditions. In each location Mrt measurements were taken in two spots – in the shade of trees and in the open grassy spaces, with high SVF. Our results demonstrate, that globe thermometers, although being relatively cheap and less complex instruments for determining Mrt, can be used to a limited extend, due to high instability of their indications under significant radiative loads.

Modeling functional relationships between morphogenetically active radiation and photosynthetic photon flux density in mango tree crown

Light is a key factor in plant ecophysiological modeling because of its crucial effects on plant growth and development. However, solar light quantity and quality change with environmental factors such as sky condition and solar elevation. When passing through a tree crown, light is modified by its interaction with the phytoelements, leaves and axes. This leads to a variability of light quantity and quality within the crown, with consequences on light-related processes such as photosynthesis and photomorphogenesis. We evaluated the effects of positional (depth within the crown) and environmental (sky condition, solar elevation) factors on light quantity and quality within the crown of the tropical evergreen mango tree. Functional relationships were modeled between morphogenetically active radiation variables that describe light quality [narrowband red (Rn), narrowband far-red (FRn), the ratio ζ=Rn : FRn, and UVA-blue (UVA-BL)] and light quantity [photosynthetic photon flux density (PPFD) and relative transmitted PPFD (TrPPFD)]. Light quantity and quality varied within the mango tree crown in a wide range similar to that of a forest. This variability was structured by the depth within the crown as well as by sky condition and solar elevation. Linear relationships linked Rn, FRn and UVA-BL to PPFD, and non-linear relationships linked ζ to TrPPFD. These relationships were strong, accurate and unbiased. They were affected by positional and environmental factors. The results suggested that these relationships were shaped by the characteristics of incident solar light and/or by the interactions between light and phytoelements. Two consequences of interest emerged from this research: i) the modeled relationships allow to infer light quality, that is difficult and time-consuming to simulate, from light quantity modeling within a tree crown, and ii) sky condition and solar elevation should be considered to improve light modeling within a tree crown.

Radiative–Convective Heating of the Surface of the Martian Descent Vehicle MSL with Taking into Account the Turbulent Nature of Flow

The three-dimensional computer model based on the Reynolds-averaged Navier–Stokes equations together with the Baldwin–Lomax and Prandtl algebraic models of turbulent mixing is used to calculate radiative–convective heat transfer on the surface of the MSL descent space vehicle. The intensification of convective heat transfer on the leeward side of the frontal aerodynamic shield and the superiority of the radiative heat flux density over the convective one on the rear surface are demonstrated. The calculations are performed using the physically and chemically nonequilibrium gas model. The results are compared with the calculations based on other computational models and the flight data on the heat load to the descent vehicle obtained during MSL descent in the dense layers of the Martian atmosphere.