Reflection Of Radiation Research Articles

A Modified Beer–Lambert–Bouguer Law for Nonrandom Distributions and Its Application in Gap Probability Calculations for Heterogeneous Canopies

AbstractThe three‐dimensional (3D) structure of vegetation canopy strongly influence the absorption and reflection of radiation at the land surface. The gap probability is one primary indicator of the canopy structure. For homogeneous canopies, where the plant elements are distributed completely randomly and statistically independent, the gap probability can be modeled with the Beer–Lambert–Bouguer law. However, this method is not suitable for nonrandom distributions. A physically based and computationally efficient algorithm is developed to address this limitation, by introducing the pair correlation function to describe the nonrandom distribution pattern. Pair correlation function is based on the distribution of distances of pairs of points, and can therefore describe random, clumped, or regular distribution patterns, and detect mixed patterns at different scales. In this paper, we take tree crown as the basic structure element, and apply the new method to calculate the gap probability. The simulations agree well with results obtained by the ray casting method for various distribution patterns. The results show that horizontal distribution of trees is one of the key factors impacts the gap probability. For the case when different patterns coexist on various scales, we can ignore the distribution pattern at larger scale, and focus on the pattern at smaller scale. When zenith angel is large, the azimuthal dependency of the gap probability should be noted.

Modeling reflection by structured building-integrated photovoltaics

Evaluating the reflection of solar radiation by Building Integrated Photovoltaics (BIPV) with structured front-glass is challenging for two reasons. First, the resulting irregular scattering of light cannot be accounted for by simple reflection models. Second, the locations where the evaluation needs to take place cannot be predicted by simple geometric considerations, as in the case of mirror-like reflection. The detailed modelling of a BIPV module featuring a periodical, linear structure based on the scanning of its surface is described. The application of the model is demonstrated in the assessment of solar reflection by a concave array of the modules. The stochastic sampling of the BIPV modules from each location in a dense sensor grid, that is required to ensure that no local concentration of reflected solar radiation is missed, is supported by re-orienting the sensors. Rather than relying on a data-driven Bidirectional Reflectance Distribution Function (BRDF) model of limited directional resolution, the geometric structure of the front-glass is modelled by modulating the normal of a mirror-like surface. The method allows an accurate and dense simulation with moderate computational demand.

Photovoltaic fields largely outperform afforestation efficiency in global climate change mitigation strategies.

Suppression of carbon emissions through photovoltaic (PV) energy and carbon sequestration through afforestation provides complementary climate change mitigation (CCM) strategies. However, a quantification of the "break-even time" (BET) required to offset the warming impacts of the reduced surface reflectivity of incoming solar radiation (albedo effect) is needed, though seldom accounted for in CCM strategies. Here, we quantify the CCM potential of PV fields and afforestation, considering atmospheric carbon reductions, solar panel life cycle analysis (LCA), surface energy balance, and land area required across different climatic zones, with a focus on drylands, which offer the main remaining land area reserves for forestation aiming climate change mitigation (Rohatyn S, Yakir D, Rotenberg E, Carmel Y. Limited climate change mitigation potential through forestation of the vast dryland regions. 2022. Science 377:1436-1439). Results indicate a BET of PV fields of ∼2.5 years but >50× longer for dryland afforestation, even though the latter is more efficient at surface heat dissipation and local surface cooling. Furthermore, PV is ∼100× more efficient in atmospheric carbon mitigation. While the relative efficiency of afforestation compared with PV fields significantly increases in more mesic climates, PV field BET is still ∼20× faster than in afforestation, and land area required greatly exceeds availability for tree planting in a sufficient scale. Although this analysis focusing purely on the climatic radiative forcing perspective quantified an unambiguous advantage for the PV strategy over afforestation, both approaches must be combined and complementary, depending on climate zone, since forests provide crucial ecosystem, climate regulation, and even social services.

Synthesis and Characterization of Antibacterial Chitosan Films with Ciprofloxacin in Acidic Conditions.

This work presents the results of research on obtaining chitosan (CS) films containing on their surface ciprofloxacin (CIP). A unique structure was obtained that not only gives new properties to the films, but also changes the way of coverage and structure of the surface. The spectroscopic test showed that in the process of application of CIP on the surface of CS film, CIP was converted from its crystalline form to an amorphic one, hence improving its bioavailability. This improved its scope of microbiological effect. The research was carried out on the reduction of CIP concentration during the process of CIP adhesion to the surface of chitosan films. The antibacterial activity of the CS films with and without the drug was evaluated in relation to Escherichia coli and Staphylococcus aureus, as well as Candida albicans and Penicillium expansum. Changes in the morphology and roughness of membrane surfaces after the antibacterial molecule adhesion process were tested with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Structural analysis of CS and its modifications were confirmed with Fourier-transform spectroscopy in the infrared by an attenuated total reflectance of IR radiation (FTIR-ATR) and solid-state nuclear magnetic resonance (NMR).

Multiphase hybrid model and thermal insulation simulation of elytra-mimetic ceramic fiber aerogel

In our previous work, the coaxial electrostatic spinning method was applied to construct nanofiber/SiBCN ceramic aerogel with an elytra-mimetic structure. The material presented excellent mechanical, insulation, oxidation resistance, and other properties. Based on preliminary experiments and literature reports, the integrated heat transfer behavior of nanofiber/SiBCN composite ceramic aerogels in high-temperature environments was affected by several factors, such as coaxial fiber size properties, fiber particle content, interactions, and spatial distribution. Moreover, the above factors overlapped and interacted with each other, and it was hard to generalize a clear law of action through traditional experiments and characterization. Therefore, the paper constructed a representative volume unit (RVE) model based on the complex spatial distribution characteristics of composite aerogels, using fractal theory, Rosseland equation theory, and multiphase model theory. This paper investigated the fiber and particle content, the size characteristics of the coaxial fibers, and the overall heat transfer process in high-temperature environments using the finite element method. The finite element simulated the effective thermal conductivity of multiphase aerogel composites under multiple parameters, such as fiber occupancy, fiber core-shell diameter ratio, temperature, and heat transfer mode. We obtained the property parameters of the complex composition of the material through fractal theory. The model was combined with finite elements to study the fiber particle content, the size characteristics of coaxial fibers, and the integrated heat transfer process in high-temperature environments. The fibers improved the absorption and reflection of thermal radiation with increasing fiber mass fraction, leading to improved ability of ceramic fiber aerogel to extinguish light. The fibers had a larger area to absorb and reflect thermal radiation. Based on the excellent extinction ability of SiC fibers, the composite ceramic aerogel had improved thermal performance at a specifically fiber-to-shell diameter ratio through a comprehensive multifactor simulation analysis.

Bioinspired Switchable Passive Daytime Radiative Cooling Coatings.

Passive daytime radiative cooling (PDRC) relies on simultaneous reflection of sunlight and radiation toward cold outer space. Current designs of PDRC coatings have demonstrated potential as eco-friendly alternatives to traditional electrical air conditioning (AC). While many features of PDRC have been individually optimized in different studies, for practical impact, it is essential for a system to demonstrate excellence in all essential aspects, like the materials that nature has created. We propose a bioinspired PDRC structure templated by bicontinuous interfacially jammed emulsion gels (bijels) that possesses excellent cooling, thinness, tunability, scalability, and mechanical robustness. The unique bicontinuous disordered structure captures key features of Cyphochilus beetle scales, enabling a thin (130 μm) bijel PDRC coating to achieve high solar reflectance (≳0.97) and high longwave-infrared (LWIR) emissivity (≳0.93), resulting in a subambient temperature drop of ∼5.6 °C under direct sunlight. We further demonstrate switchable cooling inspired by the exoskeleton of the Hercules beetle and mechanical robustness in analogy to spongy bone structures.

Chemical sensors based on photonic colloidal crystals

Objectives. The paper analyzes the results of research into the formation of photonic crystal structures from polymer microspheres and the mechanisms of spectral shifts during selective reflection of non-monochromatic incident radiation from them in the visible and infrared light, as well as the use of polymer microspheres as sensors for detecting chemical substances having similar structures.Results. Research carried out at the Ya.K. Syrkin Department of Physical Chemistry in the Institute of Fine Chemical Technologies of the RTU MIREA is presented. Issues related to the detection of substances with similar chemical structure using sensors based on photonic crystals made of polystyrene microspheres 160–300 nm in size, are considered. Spectral shifts of the reflected radiation from the crystal surface are registered in the visible spectrum when substances in the liquid or gas phase are detected by the crystal surface.Conclusions. The method of electrophoretic deposition of colloidal particles in the form of polymeric microspheres on conducting surfaces can be used to create ordered structures over large areas. However, the detection of individual compounds by the optical method is impossible without controlling the kinetics of spectral shifts of reflected radiation from the surface of photonic colloidal crystals. The spectral characteristics of such radiation are directly related to the particle sizes that determine the period of the crystal lattice. The diffusion of chemical substances into a photonic crystal, which results in a swelling of the particles forming it and a shift in the spectrum of reflected radiation, is determined by a change in the period of the crystal lattice due to a change in the size of these particles A kinetic model of swelling polymer microspheres, which describes the diffusion of substances into porous polymer particles, is proposed. An excess amount of substance deposited on the surface of a photonic crystal above the limit is shown to lead to its degradation, which is manifested in the “fading” of the crystal surface and the concomitant disappearance of narrow peaks of reflected radiation.

A comparative simulation between monofacial and bifacial PV modules under palestine conditions

During the last period, solar energy gained a lot of attraction and is expected to be the replacement for non-renewable energy due to its great potential and advantages, one of these advantages is that solar energy is scalable, which means it can be used on an industrial scale or lesser, another advantage is that solar energy is a clean source, this means it causes no pollution to the environment, in addition, solar energy is the future, as its cost is going down and non-renewable energy is becoming more and more expensive. This project aims to conduct a comparative analysis of the performance of bifacial and monofacial solar panels under diverse conditions. The investigation involves examining the influence of varying albedo levels and the type of surface beneath the PV panels, including sand, white paint, black asphalt, or artificial grass. The renowned software tool PVsyst will be employed to simulate and analyze PV systems. The location selected for this study is An-Najah National University in Nablus, Palestine. The PV panels will be oriented towards the true south, and a tilt angle of 28˚ will be employed. Through meticulous simulations and thorough analysis, this research seeks to provide comprehensive insights into the contrasting performance characteristics of bifacial and monofacial solar panels across different environmental contexts. The ultimate objective is to contribute valuable knowledge regarding the suitability and optimal utilization of these PV technologies. The study aims to evaluate and compare the electrical output, energy yield, and overall performance of bifacial and monofacial solar panels under different scenarios. The project will analyze factors such as the energy gain achieved by the bifacial panels due to rear-side irradiance reflection, the impact of albedo on the performance of bifacial panels, and the influence of shading on both panel types.

Artificial Skin with Patterned Stripes for Color Camouflage and Thermoregulation.

Chameleons are famous for their quick color changing abilities, and it is commonly assumed that they do this for camouflage. However, recent reports revealed that chameleons also change color for body temperature regulation. Inspired by the structure of the panther chameleon's skin, a stripe-patterned poly(N-isopropylacrylamide) (PNIPAM) and polyacrylamide (PAM) hydrogel film with a laminated structure is fabricated in this work; thus, both camouflage and thermoregulation can be achieved through controlling Vis and NIR light effectively. For the PNIPAM stripe, the upper layer is the native PNIPAM hydrogel and the lower layer is the carbon nanotube-composited PNIPAM hydrogel. Thus, the PNIPAM stripe is capable of reaching 28 °C at a low environmental temperature (12 °C) and a low radiation intensity (20 mW cm-2), while preventing the body temperature from rising by changing to white under a strong radiation intensity (100 mW cm-2). For the PAM stripe, the upper layer combines colloidal photonic crystals and displays a tunable structural color by stretching, and the lower layer is mixed with PNIPAM microgels for thermal regulation. Through the fabrication of multifunctional patterns, the film can achieve both dynamic structural color and thermoregulation by precisely controlling solar radiation absorption, scattering, and reflection. More importantly, in the stripe-patterned system, the shrinkage of the PNIPAM stripes can effectively trigger the elongation of the PAM stripe, which endows the structural color changing process to be self-powered completely. The performances show that the stripe-patterned film may have potential applications in intelligent coatings, especially in areas with large temperature differences during the day such as high plains.

THE NDVI INDEX CHANGE OF THE CARPATHIAN REGION OF UKRAINE DURING 2000-2022

Systematic monitoring of the Carpathian region is necessary to preserve its unique natural resource potential. The NDVI index, or - Normalized Differential Vegetation Index, - is a convenient and informative indicator of the state of the vegetation cover, and is calculated on the basis of satellite data on the absorption and reflection of red and near-infrared radiation by the studied surface.
 To study the dynamics of vegetation index values and the state of the vegetation cover of the Carpathian region, images from the space projects Landsat 7 and 8 for the years 2000, 2013, 2020, 2021 and 2022 were downloaded and processed. The best indicator for analyzing changes in the state of vegetation cover in space and time is the integral index NDVImean. For 12 out of 15 processed images, the highest value of the integral index NDVImean=0.40-0.42 was found for polygon 1, which covers part of the Transcarpathian region. The lowest values of 0.13-0.16 were found for polygon 3, which covers parts of the Lviv, Ivano-Frankivsk, and Ternopil regions. The values of the areas covered with healthy or dense vegetation, for which NDVI˃0.33, were calculated. The maximum value of this indicator was 81.54% for polygon 1 in 2021, and the minimum was - 52.89% - for the polygon 3 in 2013.
 Keywords: Carpathian region; vegetation cover; vegetation index; multispectral analysis; raster; extent.

Reflection of the Electromagnetic Wave from the Region of Electron Cyclotron Absorption in Thermonuclear Plasma

A new approach to the problem of the passage of the extraordinary wave through the region of the electron–cyclotron resonance in inhomogeneous plasma was considered in the framework of the full set of Maxwell’s equations, taking into account the effects of spatial dispersion and resonance dissipation. For the model one-dimensional geometry, field distributions were calculated in the vicinity of the cyclotron resonance at the second harmonic for the normal incidence of the extraordinary wave and the reflection, transmission, and absorption coefficients were found depending on the parameters of the resonance region. As a result, the fine effect of the reflection of electromagnetic radiation from the cyclotron resonance region in transparent plasma was described and the results were compared with the observations of this effect in the experiments on the microwave heating of the plasma at the L-2M stellarator.

Reflection of the Electromagnetic Wave from the Region of Electron Cyclotron Absorption in Thermonuclear Plasma

A new approach to the problem of the passage of the extraordinary wave through the region of the electron–cyclotron resonance in inhomogeneous plasma was considered in the framework of the full set of Maxwell’s equations, taking into account the effects of spatial dispersion and resonance dissipation. For the model one-dimensional geometry, field distributions were calculated in the vicinity of the cyclotron resonance at the second harmonic for the normal incidence of the extraordinary wave and the reflection, transmission, and absorption coefficients were found depending on the parameters of the resonance region. As a result, the fine effect of the reflection of electromagnetic radiation from the cyclotron resonance region in transparent plasma was described and the results were compared with the observations of this effect in the experiments on the microwave heating of the plasma at the L-2M stellarator.

Changes in Snow Surface Albedo and Radiative Forcing in the Chilean Central Andes Measured by In Situ and Remote Sensing Data

Snow-covered regions are the main source of reflection of incident shortwave radiation on the Earth’s surface. The deposition of light-absorbing particles on these regions increases the capacity of snow to absorb radiation and decreases surface snow albedo, which intensifies the radiative forcing, leading to accelerated snowmelt and modifications of the hydrologic cycle. In this work, the changes in surface snow albedo and radiative forcing were investigated, induced by light-absorbing particles in the Upper Aconcagua River Basin (Chilean Central Andes) using remote sensing satellite data (MODIS), in situ spectral snow albedo measurements, and the incident shortwave radiation during the austral winter months (May to August) for the 2004–2016 period. To estimate the changes in snow albedo and radiative forcing, two spectral ranges were defined: (i) an enclosed range between 841 and 876 nm, which isolates the effects of black carbon, an important light-absorbing particle derived from anthropogenic activities, and (ii) a broadband range between 300 and 2500 nm. The results indicate that percent variations in snow albedo in the enclosed range are higher than in the broadband range, regardless of the total amount of radiation received, which may be attributed to the presence of light-absorbing particles, as these particles have a greater impact on surface snow albedo at wavelengths in the enclosed band than in the broadband band.

DNA Methylation and Counterdirectional Pigmentation Change following Immune Challenge in a Small Ectotherm.

AbstractBy allowing for increased absorption or reflectance of solar radiation, changes in pigmentation may assist ectotherms in responding to immune challenges by enabling a more precise regulation of behavioral fever or hypothermia. Variation in epigenetic characteristics may also assist in regulating immune-induced pigmentation changes and managing the body's energetic reserves following infection. Here, we explore how dorsal pigmentation, metabolic rate, and DNA methylation in the Florida scrub lizard (Sceloporus woodi) respond to two levels of immune challenge across two habitat types. We found changes in pigmentation that are suggestive of efforts to assist in behavioral fever and hypothermia depending on the intensity of immune challenge. We also found correlations between DNA methylation in liver tissue and pigmentation change along the dorsum, indicating that color transitions may be part of a multifaceted immune response across tissue types. The relationship between immune response and metabolic rate supports the idea that energetic reserves may be conserved for the costs associated with behavioral fever when immune challenge is low and the immune functions when immune challenge is high. While immune response appeared to be unaffected by habitat type, we found differences in metabolic activity between habitats, suggesting differences in the energetic costs associated with each. To our knowledge, these results present the first potential evidence of pigmentation change in ectotherms in association with immune response. The relationship between immune response, DNA methylation, and pigmentation change also highlights the importance of epigenetic mechanisms in organism physiology.

Plasmons in AlGaN/GaN grating-gate structure probing with 300 K background illumination

We show that terahertz plasmons in AlGaN/GaN grating-gate structures efficiently modulate the reflection of room temperature thermal radiation, leading to spectra that are in agreement with the measurements of plasmon absorption using high-power external sources. For typical samples of a few square millimeters in size, the reflected radiation intensity is relatively weak, and measurements need the use of gate voltage plasmon modulation and lock-in detection techniques. We show that unintentional use of lock-in techniques may lead to artifacts and demonstrate what kind of special precautions need to be taken into account. We show that drain voltage modulation also leads to modulation of the reflected thermal radiation by plasmons. Our results are of key importance for the research on new resonant plasmon-based terahertz sources because of the always present superposition of electrically excited terahertz emission and background radiation reflected from the structures.

Spatial Association Rules and Thermal Environment Differentiation Evaluation of Local Climate Zone and Urban Functional Zone

Urban heat islands (UHIs) caused by urbanization have become a major issue affecting the sustainable development of the ecological environment. The distribution of UHIs is mainly affected by the reflection and transmission of heat radiation caused by differences in urban spaces, and the anthropogenic heat emissions caused by social activities. At present, the research on the urban thermal environment involves two spatial classification systems: local climate zone (LCZ), based on urban morphology and spatial patterns; and urban functional zone (UFZ), based on socio-economic activities. It is not clear whether there are association rules between these two systems in different cities. Against this background, this study explores the association rules between the UFZ and LCZ classification systems using the selected Chinese cities in different regions as typical examples. Our results confirm that there are common association rules from UFZ to LCZ, as the form of buildings is greatly influenced by the types of functional areas in urban construction. Specifically, the medical zone corresponds to the compact mid-rise zone (LCZ2); the business service area and the office area also correspond to the compact zone (LCZ1-LCZ3); and the industrial area corresponds to the compact low-rise zone (LCZ3). These functional zones have the same association rules in different cities. The cross-regional mining of the relationship between different urban functional systems will help to coordinate different planning departments and carry out the integration of multiple spatial plans. Furthermore, we found that LCZ has a better differentiation effect on the surface temperature through our comparison research, which makes it more suitable as a reference for research on the thermal environment and the heat island effect.

Promising Smart Materials for Radioelectronics

The investigations of a multilayer material – a polymeric radio-transparent electrically conductive film of polyaniline with a concentration of 5, 10 and 50 % by weight on a radio-transparent fiberglass substrate were carried out. Such materials are multifunctional – the material itself has the required characteristics, but when it is exposed to external electromagnetic radiation, it provides shielding functions. Electrically conductive polymer samples (polyaniline film) deposited on a fiberglass substrate have low attenuation in the 8–12 GHz transparency band, low electromagnetic radiation reflection coefficient, high conductivity and performance characteristics, as well as manufacturability.

Study of the Application of FY-3D/MERSI-II Far-Infrared Data in Wildfire Monitoring

In general, the far-infrared channel in the wavelength range of 10.5–12.0 µm plays an auxiliary role in wildfire detection as its sensitivity to high-temperature targets is far lower than the mid-infrared channel in the wavelength range of 3.5–4.0 µm at the same spatial resolution (1 km, which is the spatial resolution of infrared channels in most satellites used for wildfire monitoring in daily operational mode). The Medium-Resolution Spectral Imager II onboard the Fengyun-3D polar orbiting meteorological satellite (FY-3D/MERSI-II) contains far-infrared channels with a spatial resolution of 250 m at the wavelengths of 10.8 μm and 12.0 μm, which promotes the application of far-infrared channels in wildfire monitoring. In this study, the features of FY-3D/MERSI-II far-infrared channels in fire monitoring are discussed. The sensitivity of 10.8 μm (250 m) to fire spots and the influence of solar radiation reflection on the infrared channels are quantitatively analyzed. The method of using 10.8 μm (250 m) as a major data source to detect fire spots is proposed, and several typical wildfire cases are used to verify the proposed method. The results show that the 10.8 μm (250 m) far-infrared channel has the same advantages as the existing method in wildfire monitoring in terms of a more precise positioning of the detected fire pixel, avoiding interference by solar radiation reflections, and reflecting stronger fire regions in large fire fields.

Integrated asymmetric cellulose aerogel membrane with triple thermal insulation and unidirectional liquid penetration for personal thermal management

With the rapid development of personal thermal management, there is an urgent need for an advanced material that can effectively integrate various thermal functions to keep body warm and cope with the cold outdoor environment. Herein, a multifunctional cellulose based asymmetric modification aerogel membrane (ACAM) encompassing thermal insulation, thermal radiation reflection, solar adsorption, and directional perspiration has been fabricated via bottom-up assembling biomass sisal fibers and pulp fibers into cellulose aerogel membrane, followed by spin-coating ionic liquid modified graphene (IGNs) and silver nanowires (AgNWs) on both sides of the cellulose aerogel membrane, respectively. The results showed that the temperature on the IGNs side is 14.2 °C higher than that of the cotton cloth after 30 s of sunlight exposure. Compared with pure cellulose aerogel membrane, the AgNWs side of ACAM has lower infrared emissivity and higher infrared reflectivity, and the temperature is reduced by 3.2 °C in indoor environment. In addition, the ACAM has asymmetric wettability, which facilitates the transfer of sweat from the hydrophobic side to the hydrophilic side and perspiration penetration was achieved in 10.6 s to obtain the comfort of wearing. The ACAM also exhibits excellent breathability, easy preparation and controllable functional structures. This work may provide a new idea for heat management and dynamic moisture to ensure maximum comfort in very harsh environments.

Competing van der Waals and dipole-dipole interactions in optical nanocells at thicknesses below 100 nm

To reliably register the absorption or selective reflection of laser radiation in a nanocell filled with a vapor of Cesium or Rubidium at thicknesses below 100 nm, it becomes necessary to increase the atomic density by heating the cell. It is shown that both atom-wall van der Waals (vdW) interactions and Dipole-Dipole (DD) Lorentz-Lorenz interactions cause a similar “red” shift in the frequency of resonances of about the same order, which largely increases the total frequency shift. Previously, unaccounted-for DD interaction led to an overestimation of the value of the C3 coefficient of the vdW interaction. We show for the first time that varying the nanocell thickness between 130 nm and 30 - 50 nm leads to a decrease of the C3 computed from the vdW “red” shift, i.e. we observe experimentally the so-called “retardation” of the vdW effect recently predicted in theoretical papers. The measurements were made using our unique nanometric-thin cells.