Surface Emissivity Research Articles

Evolution of Increased Volcanic Activity in Arjuno-Welirang Based on LST Analysis of Landsat 8 Satellite Imagery Using GEE Cloud Computing

Typically, monitoring the volcanic activity of a volcano is carried out using volcanic seismic methods. However, this method is technically less flexible. Volcano seismic data is not freely available. Access to these data centers must be authorized by the data authority. Therefore, it is necessary to use other methods as an alternative. The alternative method used in this study is remote sensing using the Landsat 8 satellite sensors. Landsat 8 satellite imagery data can be freely accessed and easily downloaded. Landsat 8 image analysis is implemented with Google Earth Engine (GEE). GEE is a remote sensing image analysis programming tool with a cloud computing platform. The GEE programming implementation is open source. With GEE, the evolution of Arjuno-Welirang volcanic activity can be monitored accurately. The use of GEE with a cloud computing platform also makes it easier to process large remote sensing data because the downloaded file's size is unlimited. GEE has successfully conducted an LST analysis on Landsat 8 satellite imagery of the Arjuno-Welirang complex area in the 2016-2021 range. The LST calculation is performed by adding the surface emissivity correction obtained based on the NDVI value. According to the results of the LST calculations that have been obtained, the surface temperature in the Arjuna Welirang Crater area experienced the highest increase in 2018, reaching 33.94 oC, with a larger contour size of thermal distribution image than the others. This increase in thermal based volcanic activity is in accordance with the increase in seismic activity monitored by the VSI (Volcanological Survey of Indonesia).

Theme: Thermal and Dynamic Study of Convection-Radiation Coupling in a Closed Enclosure

In this work, we present a two-dimensional study of natural convection in a square air-filled cavity whose two vertical sides are subjected to a temperature difference, while the other two horizontal ones are adiabatic. The numerical method used is that of finite elements used in the COMSOL calculation code. We first studied pure natural convection, by varying the Rayleigh number from to , then its coupling with surface radiation, by varying the emissivity of the cavity surfaces from 0 to 0.6. The results are presented in the form of isotherms, pressure, current etc. It appears from this study that for a Rayleigh number less than 100, the fluid presents a vertical thermal stratification due to heat transfer only by conduction which does not generate any convective flow. The presence of surface radiation does not modify the equations governing fluid movements but only alternates the thermal boundary conditions. The coupling of natural convection and surface radiation occurs only through thermal boundary conditions. The variation in the emissivity of the walls does not influence the temperature isotherms.

Modern Scanning Electron Microscopy. 2. Test objects for Scanning Electron Microscopy

The review of the test objects intended for calibration of scanning electron microscopes and researches to secondary electronic emission of a relief surface of a solid state in scanning electron microscope is carried out. The test objects are divided on two parameters – kind of a relief and structure of a relief. By the form of relief the test objects are divided on single, pitch and periodic. On a structure of a relief of the test objects are divided into objects with a rectangular structure and objects with a trapezoid structure with the large and small corners of an inclination of lateral walls. The examples of such the test objects are given. Their characteristics and methods of certification of parameters are described. The advantages and lacks of the test objects are considered. Is shown, that the best characteristics have the tests objects representing pitch structures consisting of trapezoid trenches with the large corners of an inclination of lateral walls. The test objects are created in monosilicon with of a surface orientation by {100} by method liquid anisotropic etching of silicon. These test objects allow defining all characteristics scanning electron microscopes, influencing on measurement of the linear sizes of relief structures used in microelectronics and nanotechnology. With their help it is possible to carry out correlation measurements, which raise accuracy of calibration scanning electron microscopes up to ten times.

Heteroepitaxy of N-polar AlN on C-face 4H-SiC: Structural and optical properties

To date, it has remained challenging to achieve N-polar AlN, which is of great importance for high power, high frequency, and high temperature electronics, acoustic resonators and filters, ultraviolet (UV) optoelectronics, and integrated photonics. Here, we performed a detailed study of the molecular beam epitaxy and characterization of N-polar AlN on C-face 4H-SiC substrates. The N-polar AlN films grown under optimized conditions exhibit an atomically smooth surface and strong excitonic emission in the deep UV with luminescence efficiency exceeding 50% at room temperature. Detailed scanning transmission electron microscopy (STEM) studies suggest that most dislocations are terminated/annihilated within ∼200 nm AlN grown directly on the SiC substrate due to the relatively small (1%) lattice mismatch between AlN and SiC. The strain distribution of AlN is further analyzed by STEM and micro-Raman spectroscopy, and its impact on the temperature-dependent deep UV emission is elucidated.

Physically Based Thermal Infrared Snow/Ice Surface Emissivity for Fast Radiative Transfer Models

Accurate thermal infrared (TIR) fast-forward models are critical for weather forecasting via numerical weather prediction (NWP) satellite radiance assimilation and operational environmental data record (EDR) retrieval algorithms. The thermodynamic and compositional data about the surface and lower troposphere are derived from semi-transparent TIR window bands (i.e., surface-sensitive channels) that can span into the far-infrared (FIR) region under dry polar conditions. To model the satellite observed radiance within these bands, an accurate a priori emissivity is necessary for the surface in question, usually provided in the form of a physical or empirical model. To address the needs of hyperspectral TIR satellite radiance assimilation, this paper discusses the research, development, and preliminary validation of a physically based snow/ice emissivity model designed for practical implementation within operational fast-forward models such as the U.S. National Oceanic and Atmospheric Administration (NOAA) Community Radiative Transfer Model (CRTM). To accommodate the range of snow grain sizes, a hybrid modeling approach is adopted, combining a layer scattering model based on the Mie theory (viz., the Wiscombe–Warren 1980 snow albedo model, its complete derivation provided in the Appendices) with a specular facet model. The Mie-scattering model is valid for the smallest snow grain sizes typical of fresh snow and frost, whereas the specular facet model is better suited for the larger sizes and welded snow surfaces typical of aged snow. Comparisons of the model against the previously published spectral emissivity measurements show reasonable agreement across zenith observing angles and snow grain sizes, and preliminary observing system experiments (OSEs) have revealed notable improvements in snow/ice surface window channel calculations versus hyperspectral TIR satellite observations within the NOAA NWP radiance assimilation system.

Radiative thermal coats for passive temperature management

Radiative thermal management has advantages in precision electronic instruments owing to zero-energy consumption and high integration convenience. The possibility to acquire high-performance thermal stability through engineering the surface emissivity of object has been investigated. Herein, developing a smart coat was reported that could passively maintain the temperature of objects (silicon chips) in a predefined thermal window to avoid overheating or overcooling in vacuum. The technique implements using a multilayer structure incorporating a 30 nm thick VO2 phase-change medium having a 300% modulation depth for emissivity under varying temperatures. In the experiment, a 1.78 μm thick smart coat could raise the temperature stability of a regular coat by ∼2.0 times. The potential of the work remains in thermal radiation for smart temperature management especially in space applications.

Development of Two-Color pyrometry for flame impingement on oxidized metal surfaces

Measuring the temperature on a metal surface exposed to flame impingement is valuable for studying heat transfer. In this study, a non-intrusive two-color pyrometry was developed. It utilized visible light cameras to measure the two-dimensional temperature distribution on different metal surfaces. The experiment involved measuring the temperature distribution of metals (stainless steel, titanium, molybdenum) ranging from 700 °C to 1200 °C under flame impingement conditions. Thermocouple measurements were used as a reference for accuracy and uncertainty assessment. Two monochrome visible-light cameras equipped with optical filters at wavelengths of 750 nm and 905 nm captured different signal intensities corresponding to relative radiation temperatures. Calibration using a black body furnace at multiple temperature points was performed to enhance measurement accuracy. The variation in correction factor was assessed for shutter speeds ranging from 0.01 s to 0.03 s. An uncertainty analysis accounted for factors such as the grey body assumption, monochromatic wavelength assumption, and thermal radiation sources, and the respective uncertainties for these factors were 4.72 %, 2.5 %, and 1.02 %. Despite the presence of severe oxidation layers on the surfaces being measured, the two-color pyrometer successfully detected surface temperatures within an acceptable margin of error; the maximum relative error between the pyrometer and thermocouples was less than 4 %. This paper presents a technique for measuring temperature that produces a two-dimensional temperature distribution. Additionally, this method mitigates the effects of changes in surface emissivity due to temperature or materials.

Towards benchmarking of urban air quality based on homogenous surface emission

Here, it is presented a possible methodology and experimental model for benchmarking of air quality in cities. The concept behind the methodology is that a city's inherent structure affects the potential for contaminant removal due to the resistance it poses to inflow. The approach is based on homogenous emission across the street surface network, representing a worst-case situation. Different levels of complexity can be used for benchmarking, making it valuable for evaluating different layouts. Additionally, an urban ventilation index suitable for these kinds of experimental studies has been suggested.

Field application of bio-foam spray to reduce ammonia emission from ammonia-rich swine manure piles

In this study, the first field-scale application of a bio-foam spray (a mixture of microbes and a surfactant) for the reduction of ammonia emitted from manure was investigated on six field swine manure piles. The objective of this study was to evaluate the odor suppression ability of bio-foam and odor degradation ability of odor-degrading bacteria loaded in the surfactant foam after covering manure piles. The size of field manure piles tested in this study ranged from 27 to 300 m3. Bio-foam spraying completely suppressed the release of the major odor component, ammonia (NH3), and odor-degrading bacteria in the bio-foam aided in the degradation of NH3 in field swine manure piles. On average, 85.7–100% of NH3 was reduced after 24–48 h of serial bio-foam spray application on the swine manure surface, while the control showed 25–42%. The reduction efficiency of NH3 by the bio-foam application was affected by the bio-foam spray frequency, ambient temperature, ventilation of the field facility, and upward airflow to the pile. The reduction in surface emission of NH3 also reduced the ambient air concentration of NH3 at the gate of the compost facility. NH3 gas measurements at a depth of 50 cm indicated that NH3-degrading bacteria infiltrated the manure and were active in biodegradation. Finally, the measured effectiveness of bio-foam application as shown by this study indicates that sprinkling bio-foam via specialized rotating sprinklers may be an efficient and uniform method for the delivery of bio-foam to wide field areas within composting facilities.

Influence of Buoyancy and Inter-Surface Radiation on Confined Jet Impingement Cooling of a Semi-Cylindrical Concave Plate

Abstract In this article, the confined jet impingement cooling of a semicylindrical concave plate is analyzed numerically. The finite volume approach is applied to two-dimensional numerical simulations in the transient regime. Air is employed as the working fluid and is regarded as nonparticipant for radiation. The investigation is done for different jet Reynolds numbers (Rej) ranging from 100 to 1000, as the Richardson number (Ri) corresponding to this interval ranges between 0.1 and 10. For any Richardson number, the modified Grashof number (Gr*) is fixed at 105. When analyzing the impact of intersurface radiation between the target plate and confined surfaces on the overall cooling performance, three emissivity values (ε= 0.05, 0.5, and 0.95) are taken into consideration. Additionally, simulations are done for the pure convective heat transfer, ignoring intersurface radiation (ε= 0.0). The influence of surface emissivity and the Richardson number on velocity, temperature, and pressure distribution in the flow domain, local dimensionless temperature (θ) alterations on the target plate and confined walls, alterations in convective (Nuc), radiative (Nur), overall Nusselt numbers (Nuovr), pressure coefficient (Cp), and ratio of radiative Nusselt number to overall Nusselt number (Nur/Nuovr) on the target plate are highlighted. The findings demonstrate that surface emissivity has a significant influence on thermal and hydrodynamic boundary layer formation, buoyancy induced flow and heat transfer, and the proportion of intersurface radiation in overall heat transfer rises as the Richardson number and surface emissivity increase. At low Richardson numbers, the pressure in the stagnation region is greater than the atmospheric pressure. However, as the buoyancy effect increases, the pressure in the stagnation region falls below the atmospheric pressure and rises toward the exit.

A straightforward spectral emissivity estimating method based on constructing random rough surfaces

Spectral emissivity is an essential and sensitive parameter to characterize the radiative capacity of the solid surface in scientific and engineering applications, which would be non-negligibly affected by surface morphology. However, there is a lack of assessment of the effect of roughness on emissivity and a straightforward method for estimating the emissivity of rough surfaces. This paper established an estimating method based on constructing random rough surfaces to predict rough surface (Geometric region) emissivity for metal solids. Based on this method, the emissivity of ideal gray and non-gray body surfaces was calculated and analyzed. The calculated and measured spectral emissivities of GH3044, K465, DD6, and TC4 alloys with different roughness were compared. The results show that the emissivity increases with the roughness degree, and the enhancement effect weakens with the increase of roughness or emissivity due to the existing limit (emissivity ε = 1.0). At the same time, the roughness would not change the overall spectral distribution characteristics but may attenuate the local features of the spectral emissivity. The estimated results are in good agreement with the experimental data for the above alloys’ rough surfaces. This study provides a new reliable approach to obtaining the spectral emissivity of rough surfaces. This approach is especially beneficial for measuring objects in extreme environments where emissivity is difficult to obtain. Meanwhile, this study promotes an understanding of surface morphology’s effect mechanism on emissivity.

Shades of grey—tire characteristics and road surface influence tire and road wear particle (TRWP) abundance and physicochemical properties

There is mounting evidence that tire wear particles can harm natural systems, but worldwide trends in car weight and car usage, mean emissions are set to increase. To control tire wear emissions and help understand fate and transport, detailed characterisation of the particles, and the relationship between road surface properties and emission profiles is needed. This study deployed a suite of experiments utilising the advanced road simulator of the Swedish National Road and Transport Research Institute to compare seasonal tire types from three brands. An extraction method was developed for a coarse (>30 µm) fraction of tire and road wear particles (TRWP), and a comprehensive physicochemical characterisation scheme applied to both TRWP and tire-tread, including microscopy, energy-dispersive X-ray spectroscopy and pyrolysis-GC/MS. Road simulator dusts and hand-picked TRWP showed differences in shape, numbers, and mass between tire types and brands, and between asphalt and cement concrete road surfaces. Contrary to accepted perceptions, tactile analyses revealed that firm-elastic TRWP comprised only a minor proportion of TRWP. Fragile and chemically distinct tire-road-derived particles, termed here sub-elastic TRWP, comprised 39–100% of TRWP. This finding raises urgent questions about overall TRWP classification and identification features, resistance to weathering, and environmental fate. At the same time, differences in TRWP generation between tire formulations, and road surfaces, show potential for controlling emissions to reduce global impacts.

Study of microchannel structures for measuring emission conductance of indium field emission electric propulsion micro-thrusters

Surface morphology of emitting tip has a significant effect on performance of Liquid-Metal Ion Sources. In this paper, fabrication technics of dynamic micro-electrochemical etching was employed to realize micro-grooves processing of emitting tip surfaces at different depths by regulating roughening time and voltage frequency. Through field emission experiments of indium Field Emission Electric Propulsion micro-thruster, we measured volt–ampere characteristic curves of a batch of emitters with different microchannel structures. By a normalization method, the effect of inconsistency of apex radius between different tips on volt–ampere characteristics was eliminated, and influence law of surface roughness on emission conductance was revealed more clearly. The test results were found to be consistent with the current–voltage characteristics which was deduced from microchannel model based on a semi-cylindrical shape. This study presents an approach for pre-estimating and optimizing the emission conductance through assessment of emitter surface roughness and substantiates the method’s viability.

Study on energy-saving potential of lowering the emissivity of unheated surfaces for floor radiant heating

It has been demonstrated that the application of low emissivity materials to unheated surfaces improves the thermal comfort level of radiant heating. However, it remains unclear whether the emissivity of unheated surfaces can shorten the response time of floor radiant heating (FRH) and whether there is energy-saving potential. Numerical simulations were conducted to determine the influence of unheated surface emissivity and wall insulation methods on the dynamic performance of FRH during intermittent operation. The results indicate that decreasing the emissivity of the unheated surface can effectively shorten the response time of FRH by 26.8 %, but at the expense of an increased start-up load. The difference between start-up load and steady heating load is between 1.8 and 2.3 times, which increases with the area of the internal insulating wall. Two energy-saving measures exhibit a "substitution" relationship that must be combined with an economic analysis to determine a reasonable implementation scheme, with the roof occupying a key position. This study provides an alternative energy-saving solution for heating and air conditioning in the hot summer and cold winter zone of China, as well as a design foundation for the promotion and application of FRH.

Modeling and validation of ablative thermal response combined with microscopic heat transfer for porous ablative materials

Porous ablative materials are the state-of-the-art thermal protection materials for extreme aerodynamic conditions during re-entry, but the precise analysis of heat transfer within microstructure and the ablative thermal response process is still a challenge. Herein, a numerical model that combines macroscopic ablative thermal response and microscopic heat transfer for porous ablative materials is presented. The microscopic heat transfer in the model is implemented through the conjugate solid and gas phases heat transfer. The model is validated by comparing the results of typical ablation cases with predictions made using another computational program PATO. In addition, analysis is performed to investigate the effect of parameters in the model such as thermal conductivity, heat capacity, surface emissivity, reaction kinetic parameters, and pressure. The results show that surface radiation is the majority of energy consumption mechanisms, and the internal temperature distribution of materials is primarily governed by thermal conductivity and heat capacity. Moreover, pressure serves as both the independent and dependent variable of thermal response, and the heat dissipation effect of pyrolysis gas exhibits a significant increase when it exceeds 10 atm. The results can improve the understanding of the ablative thermal response process and highlight areas for optimizing the design of TPS materials.

Heat transfer analysis and thermo-mechanical property of M-shape metal-rubber at high-temperature

Particular attention is given to the M-shape metal-rubber (MMR), which is a porous material with cushioning characteristics and excellent heat resistance coated in pipelines. The heat transfer characteristics and thermo-mechanical property of MMR has not been clear due to its complicated micro-porous structures and the coupling effect between structure and performance. In this work, the influence of different parameters (emissivity, density and gap distance) on the equivalent thermal conductivity of MMR were considered at the mesoscopic model level. In addition, thermal stress at different temperatures was used as predefined fields for thermal-mechanical coupling to analyze the transformations of performance. The results indicate that surface emissivity and cavity emissivity during heat transfer exhibit an inverse relationship with MMR thermal conductivity. Furthermore, it is observed that natural convection has the most significant impact on thermal conductivity. And, the thermal conductivity is negative correlation with density and gap distances. Under cyclic loading, stress concentration and plastic strain occur in MMR, and residual thermal stress is generated. The secant stiffness exhibits a positive correlation with temperature, while the loss factor demonstrates a negative correlation, primarily due to thermal expansion.

A WISPR of the Venus Surface: Analysis of the Venus Nightside Thermal Emission at Optical Wavelengths

Parker Solar Probe (PSP) conducted several flybys of Venus while using Venus’ gravity for orbital adjustments to enable its daring passes of the Sun. During these flybys, PSP turned to image the nightside of Venus using the Wide-field Imager for Solar PRobe (WISPR) optical telescopes, which unexpectedly observed Venus’ surface through its thick and cloudy atmosphere in a theorized, but until-then unobserved near-visible spectral window below 0.8 μm. We use observations taken during PSP’s fourth Venus gravity assist flyby to examine the origin of the Venus nightside flux and confirm the presence of this new atmospheric window through which to observe the surface geology of Venus. The WISPR images are well explained by emission from the hot Venus surface escaping through a new atmospheric window in the optical with an overlying emission component from the atmosphere at the limb that is consistent with O2 nightglow. The surface thermal emission correlates strongly with surface elevation (via temperature) and emission angle. Tessera and plains units have distinct WISPR brightness values. Controlling for elevation, Ovda Regio tessera is brighter than Thetis Regio; likewise, the volcanic plains of Sogolon Planitia are brighter than the surrounding regional plains units. WISPR brightness at 0.8 μm is predicted to be positively correlated to FeO content in minerals; thus, the brighter units may have a different starting composition, be less weathered, or have larger particle sizes.

Development of the SURface Fast Emissivity Model for Ocean (SURFEM‐Ocean) Based on the PARMIO Radiative Transfer Model

AbstractA Passive and Active Reference Microwave to Infrared Ocean (PARMIO) physical radiative transfer model has been selected by an international team of experts to be used as a community ocean surface emissivity model. A fast version of this physical community model is developed within the framework of European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Numerical Weather Prediction Satellite Application Facilities visiting scientist programme: the SURface Fast Emissivity Model for Ocean (SURFEM‐Ocean), for implementation in the Radiative Transfer code for TOVS (RTTOV) as an alternative/replacement of the well‐known FAST microwave Emissivity Model (FASTEM). First, the configuration of the PARMIO model is adapted to microwave frequencies from 500 MHz to 700 GHz, and issues observed in the preliminary studies with cold sea surface temperatures (SST) and high ocean wind speeds (OWS) are corrected. Second, an artificial neural network method is used to reproduce the results of the PARMIO model much faster. The computation of the analytical Jacobians is also implemented. Finally, SURFEM‐Ocean results are compared with satellite observations and other ocean emissivity models. SURFEM‐Ocean extends the capability of FASTEM. It computes emissivities from 500 MHz to 700 GHz, for all incidence angles, for the fourth Stokes polarizations, for OWS from 0 to 50 m/s, SST from −2 to 30°C, sea surface salinity from 0 to 40 psu, and for all wind directions.

Study on predicting the radiant heat flow rate of floor surface of radiant floor heating

Radiant heat flow rate of radiant surface is crucial for radiant floor heating design and terminal selection. We found that the present empirical formula to predict radiant heat flow rate of radiant surface has limits under varied room size and surface emissivity circumstances. Wall insulation conditions also have substantial influences on the operating efficiency of floor radiant heating. Adopting machine learning algorithms and backward selection method, a two-layer Neural Network model was demonstrated to have good accuracy and requisite relevant features for new empirical formula was identified. The new formula containing the information of room depth, weighted radiant surface area, insulation conditions, indoor air temperature and radiant surface temperature as independent variables exhibits great accuracy with R-squared of 0.97 and RMSE of 2.74. The substitution of AUST with indoor air temperature can increase the prediction accuracy. Analysis reveals structural pattern and indicates interaction between wall insulation and non-radiative surface with low emissivity. We propose the use of non-radiant surfaces with low emissivity as a passive energy-saving technique for radiant floor heating. And the updated empirical formula can increase its application scenarios, and aid promote application of FRH and new passive technique.

Single field-of-view sounder atmospheric product retrieval algorithm: establishing radiometric consistency for hyper-spectral sounder retrievals

Abstract. The single field-of-view (SFOV) sounder atmospheric product (SiFSAP) retrieval algorithm has been developed to address the need to retrieve high-spatial-resolution atmospheric data products from hyper-spectral sounders and ensure the radiometric consistency between the retrieved properties and measured spectral radiances. It is based on an integrated optimal-estimation inversion scheme that processes data from the satellite-based synergistic microwave (MW) and infrared (IR) spectral measurements from advanced sounders. The retrieval system utilizes the principal component radiative transfer model (PCRTM), which performs radiative transfer calculations monochromatically and includes accurate cloud-scattering simulations. SiFSAP includes temperature, water vapor, surface skin temperature and emissivity, cloud height and microphysical properties, and concentrations of essential trace gases for each SFOV at a native instrument spatial resolution. Error estimations are provided based on a rigorous analysis for uncertainty propagation from the top-of-atmosphere (TOA) spectral radiances to the retrieved geophysical properties. As a comparison, the spatial resolution for the traditional hyper-spectral sounder retrieval products is much coarser than the native resolution of the instruments due to the common use of the “cloud-clearing” technique to compensate for the lack of cloud-scattering simulation in the forward model. The degraded spatial resolution in traditional cloud-clearing sounder retrieval products limits their applications for capturing meteorological or climate signals at finer spatial scales. Moreover, a rigorous uncertainty propagation estimation needed for long-term climate trend studies cannot be given due to the lack of direct radiative transfer relationships between the observed TOA radiances and the retrieved geophysical properties. With the advantages of the higher spatial resolution; the simultaneous retrieval of atmospheric, cloud, and surface properties using all available spectral information; and the establishment of “radiance closure” in the sounder spectral measurements, the SiFSAP provides additional information needed for various weather and climate studies and applications using sounding observations. This paper gives an overview of the SiFSAP retrieval algorithm and assessment of SiFSAP atmospheric temperature, water vapor, clouds, and surface products derived from the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) data.