Emissivity Values Research Articles

In situ melt pool measurements for laser powder bed fusion using multi sensing and correlation analysis

Laser powder bed fusion is a promising technology for local deposition and microstructure control, but it suffers from defects such as delamination and porosity due to the lack of understanding of melt pool dynamics. To study the fundamental behavior of the melt pool, both geometric and thermal sensing with high spatial and temporal resolutions are necessary. This work applies and integrates three advanced sensing technologies: synchrotron X-ray imaging, high-speed IR camera, and high-spatial-resolution IR camera to characterize the evolution of the melt pool shape, keyhole, vapor plume, and thermal evolution in Ti–6Al–4V and 410 stainless steel spot melt cases. Aside from presenting the sensing capability, this paper develops an effective algorithm for high-speed X-ray imaging data to identify melt pool geometries accurately. Preprocessing methods are also implemented for the IR data to estimate the emissivity value and extrapolate the saturated pixels. Quantifications on boundary velocities, melt pool dimensions, thermal gradients, and cooling rates are performed, enabling future comprehensive melt pool dynamics and microstructure analysis. The study discovers a strong correlation between the thermal and X-ray data, demonstrating the feasibility of using relatively cheap IR cameras to predict features that currently can only be captured using costly synchrotron X-ray imaging. Such correlation can be used for future thermal-based melt pool control and model validation.

Extended Rift‐Associated Volcanism in Ganis Chasma, Venus Detected From Magellan Radar Emissivity

AbstractExploration of Venus in the 1970–1990s revealed that the geology of Venus, the most Earth‐like of the terrestrial planets, was decidedly un‐Earth‐like, with no plate tectonics, and no record of the first 80% of its history. A major outstanding question is whether Venus is still volcanically active today. We find that regions of Ganis Chasma have low radar emissivity values, due to low volumes of high dielectric minerals formed by surface‐atmosphere weathering on the timescales of around 10 s Ma. This confirms the presence of geologically recent volcanism in association with this major tectonic rift zone. The spatial correspondence of this emissivity signature with transient thermal anomalies suggests that Venus has been volcanically active at this site for at least the last few decades, a prediction that can be tested with space missions to Venus in the coming decade.

ANALISIS HOTSPOT PADA PMS GARDU INDUK 150 KV RAWADENOK DEPOK MENGGUNAKAN METODE THERMOVISION

Abstract
 
 Hotspot analysis at PMS Substation 150 kV Rawadenok Depok using the thermovision method was initiated based on hotspot events on Contact Finger phase S and Disconnecting Switch phase S. This analysis uses the Thermovisi Flir 400 tool as a means of checking high current temperatures that occur in Contact Finger phase S and Disconnecting Switches. The function of this thermovision is to measure the value of the ratio of the energy radiated by an object to the energy radiated by a black body at the same temperature and wave. Then measure the accuracy of Thermovisi starting from the value when checking, testing emissivity values, precision test values, accuracy values and repairs at hotspot points. From the results of the calculation of thermovision accuracy at Bay Cimanggis 1 & 2, it can be concluded that the temperature of the clamps and conductors shows that the conditions are still good. Where the RSM value of 27 samples is 0.4751, and has a coefficient variation (CV) of 0.1% and is categorized as good with a reference of no more than 2%, and has an accuracy value of 97.51%. Prior to the improvement of the hotspot points on Contact Finger it reached 115 oC and the DS Line S phase reached 103 oC after the temperature improvement returned to normal with Contact Finger reaching 36
 oC and the DS Line S phase reaching 31.2 oC.
 
 Keywords : PMS, Thermovisi, Hotspot, Emisivitas

Thermography for disease detection in livestock: A scoping review.

Infra-red thermography (IRT) offers potential opportunities as a tool for disease detection in livestock. Despite considerable research in this area, there are no common standards or protocols for managing IRT parameters in animal disease detection research. In this review, we investigate parameters that are essential to the progression of this tool and make recommendations for their use based on the literature found and the veterinary thermography guidelines from the American Academy of Thermology. We analyzed a defined set of 109 articles concerned with the use of IRT in livestock related to disease and from these articles, parameters for accurate IRT were identified and sorted into the fields of camera-, animal- or environment-related categories to assess the practices of each article in reporting parameters. This review demonstrates the inconsistencies in practice across peer-reviewed articles and reveals that some important parameters are completely unreported while others are incorrectly captured and/or under-represented in the literature. Further to this, our review highlights the lack of measured emissivity values for live animals in multiple species. We present guidelines for the standards of parameters that should be used and reported in future experiments and discuss potential opportunities and challenges associated with using IRT for disease detection in livestock.

Offset of MODIS land surface temperatures from in situ air temperatures in the upper Kaskawulsh Glacier region (St. Elias Mountains) indicates near-surface temperature inversions

Abstract. Remote sensing data are a crucial tool for monitoring climatological changes and glacier response in areas inaccessible for in situ measurements. The Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) product provides temperature data for remote glaciated areas where air temperature measurements from weather stations are sparse or absent, such as the St. Elias Mountains (Yukon, Canada). However, MODIS LSTs in the St. Elias Mountains have been found in prior studies to show an offset from available weather station measurements, the source of which is unknown. Here, we show that the MODIS offset likely results from the occurrence of near-surface temperature inversions rather than from the MODIS sensor’s large footprint size or from poorly constrained snow emissivity values used in LST calculations. We find that an offset in remote sensing temperatures is present not only in MODIS LST products but also in Advanced Spaceborne Thermal Emissions Radiometer (ASTER) and Landsat temperature products, both of which have a much smaller footprint (90–120 m) than MODIS (1 km). In all three datasets, the offset was most pronounced in the winter (mean offset >8 ∘C) and least pronounced in the spring and summer (mean offset <2 ∘C). We also find this enhanced seasonal offset in MODIS brightness temperatures, before the incorporation of snow surface emissivity into the LST calculation. Finally, we find the MODIS LST offset to be consistent in magnitude and seasonal distribution with modeled temperature inversions and to be most pronounced under conditions that facilitate near-surface inversions, namely low incoming solar radiation and wind speeds, at study sites Icefield Divide (60.68∘N, 139.78∘ W; 2,603 m a.s.l) and Eclipse Icefield (60.84∘ N, 139.84∘ W; 3017 m a.s.l.). Although these results do not preclude errors in the MODIS sensor or LST algorithm, they demonstrate that efforts to convert MODIS LSTs to an air temperature measurement should focus on understanding near-surface physical processes. In the absence of a conversion from surface to air temperature based on physical principles, we apply a statistical conversion, enabling the use of mean annual MODIS LSTs to qualitatively and quantitatively examine temperatures in the St. Elias Mountains and their relationship to melt and mass balance.

Simulation study for the characterization of anode shape effect on the electron beam emittance of thermionic electron gun

A systematic method had been used to develop the anode electrode shape of the thermionic electron gun by studying its effect on the emittance value, where the emittance parameter has been considered an important criterion for determining the fineness of the beam propagation. In this study, it has been found that the extended field outside the electron gun has a negative effect on the electron beam emittance parameter. A new shape of the anode has been developed and introduced in this research work to eliminate the unwanted field at the electron beam side. The cylindrical shape of the anode, which encapsulates the Wehnelt cylinder, has the effect of eliminating the adverse stray field, hence the enhancement of the beam emittance values. The new design is developed to be used in the illumination system of the electron microscopes where the highest laminar flow of the electron beam is needed.

High temperature spectral emissivity of glass and crystal-bearing basalts

Temperature is a key parameter controlling the rheology of lava flows. However, the unpredictable hazard of eruptions prevents direct measurements of hot volcanic bodies. Thus, the temperature of lava products is mostly retrieved by remote sensing techniques (ground- or satellite-based detectors) build on measuring infrared (IR) radiance. These well-established techniques are however subjected to important errors related to the poor knowledge of one of the most critical parameters, namely spectral emissivity. The aim of our study is to fill this gap by exploring the emissivity–temperature relationship of three different basalts. We performed in situ emissivity measurements at high temperatures (up to 1800 K) over a wide spectral range (350–8000 cm−1; 1.25–28.6 μm), using a non-contact IR apparatus. To unravel the complex radiative behavior of the samples with temperature, structural, chemical and textural analyses using Raman spectroscopy, XRD, DSC, SEM, EMPA and TEM were systematically performed. Our results show that spectral emissivity varies with temperature, wavenumber, and the sample degree of polymerization combined with total FeO content. Spectral emissivity is greatly affected by the crystallization of Fe-Mg-rich crystals at the micro-scale. Consequently, this study proves that spectral emissivity cannot be assumed constant for a single magmatic composition. Finally, our laboratory-measured values of spectral emissivity allowed refining the remote sensing temperature of the 2014–2015 Holuhraun eruption (Bárðarbunga, volcano) by 50 K in average. These new insights will ultimately reduce uncertainties in temperature estimates based on IR technology, information that are crucial to improve hazard assessment in volcanic crisis.

Characteristics of Al & Ti oxide-thin films for thermal solar energy selective absorption applications

Controlled oxidation of sputtered layers of Ti and Al results oxide layers with nano-sized thickness comparable to thermal solar selective absorber layers. In this work, RF magnetron sputtering was used to obtain thin layers of Al and Ti on substrates of stainless steels (St. St). Deposited thin films were oxidized at 400 °C and 800 °C for 4 hours and 1 hour, respectively. The as-deposited Ti, and Al layers were air–oxidized and their optical absorbance and emittance were studied. Microstructure, surface topography, structure and new phases formed after oxidation were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD). Thin films optical properties were investigated by spectrophotometer & Fourier Transform Infrared (FTIR) Spectroscopy. The new microstructures exhibited a dual metallic and oxide nature. Deposited thin film of Ti had maximum absorbance and lowest emittance about 90% and 1.8% respectively; while after oxidation, the deposited layers changed their selective absorbance pattern. The absorbance values increased, and the emittance values decreased for all wave lengths in the infrared (IR) range. The effect of the oxidation process of both Ti thin film and Al thin film was compared. The Al thin film showed lower absorbance in as-deposited and oxidized states.

Fabrication of low emissivity paint for thermal/NIR radiation insulation for domestic applications

Recently, low-emissivity paint has gained more importance than commercial paints. Low emissivity (Low-E) Paint also termed as a coating for radiation control, in which the emissivity of radiations of longer waves are reduced dramatically (i.e., the emissivity of commercially available paint is 0.9) by imparting low emissivity particles in the base paint but not suitable to reduce near-infrared radiation. Commercially available paints as of today have minimum of 0.7 emissivity and it does not give any significant energy saving. The low emissivity property of paint makes it particularly suitable for reducing the radiative heat exchange in many domestic applications i.e., home electronics, building construction components, roof surfaces, heat storage tanks, and pipes, etc in result, low power required to heat or cool the building in respective whether conditions. In this work, different samples of white paint were prepared in the lab by using a low shear mixer (mechanical stirrer) under very controlled conditions and studied the results of dry paint films to reduce the thermal emissivity then commercially available paint. Then we investigate the drying time of the wet paint films and analyze thermal heat into visible light through thermal imaging camera, Crosshatch, and IR transmission. We also studied the emissivity through ET-100 and aging stability through a weather-o-meter instrument, which investigated that emissivity value achieved in the range of 0.4–0.6 than commercial paints. The results showed that paint exhibits an acceptable aesthetic emissivity value of ∼0.60. It was calculated theoretically that by the use of this novel Low-E paint, annually about 20%–25% less energy will be consumed in building for cooling or heating.

Research on the normal emissivity of graphite between 150 and 500 °C by an infrared camera for nuclear fusion devices

• An emissivity measurement equipment by using an infrared camera is constructed and calibrated by a blackbody furnace with a suitable emissivity model. • By using an infrared camera with no filter (band wavelength range of 7.5 μm–13 μm), a 10.2 ± 0.1 μm filter, and a 10.8 ± 0.19 μm filter, the relationship between the temperature and emissivity of graphite and the residual between data and model are obtained respectively and compared. • The emissivity of graphite at different roughness is studied, and uncertainty quantification is used to provide an error estimate for the resulting curves. Due to the advantages of high-temperature resistance, low thermal expansion coefficient, and thermal shock resistance, etc., graphite is regarded as one of the materials for the first wall of nuclear fusion devices. The real-time monitoring of temperature distribution of the first wall based on an infrared camera is widely used to guarantee the stable operation of devices. To accurately measure the temperature of the first wall, it is important to measure the normal emissivity of graphite. However, the emissivity of graphite is affected by many factors. For example, the effect of the surface layers, like carbon-hydro layers-layers, will influence the measurement of the emissivity. The ambition of this work is to study the relationship between graphite emissivity and infrared camera with filters of different wavelengths and the roughness of graphite, and then give the proposed emissivity model to improve the accuracy of graphite surface temperature measurement. The experiment is carried out with a FLIR infrared camera and calibrated by using a blackbody furnace. The emissivity at given temperatures is systematically investigated. By using an infrared camera with no filter (band wavelength range of 7.5–13 μm), a 10.2 ± 0.1 μm filter, and a 10.8 ± 0.19 μm filter, this paper studies the relationship between the temperature and emissivity of graphite from 150 °C to 500 °C and calculates the relative error of temperature measurement respectively. A suitable fitting model which fits emissivity curves is selected. The measurement results show the use of a 10.2 μm filter to measure the graphite surface temperature has the smallest relative error, the range is 0.90%∼1.17%. The emissivity of graphite with different roughness is also studied. At the same temperature, the greater the roughness of the graphite surface, the higher the emissivity value. The uncertainty of the emissivity measurement is analyzed, and its value is 0.0099–0.0211. The graphite surface temperature measurement method based on the emissivity model proposed in this paper provides useful references for the non-contact temperature measurement of the first wall in nuclear fusion devices. The research results can be used as a reference for plasma experiments in some fusion devices and other similar applications.

Titanium and Silicon Dioxide-Coated Fabrics for Management and Tuning of Infrared Radiation.

Far infrared radiation (FIR) is emitted by every body at a given temperature, including the human body. FIR ranging between 4–14 μm is considered useful for cell growth, and the human body emits a maximum of infrared (IR) radiation at the wavelength of approximately 9.3 µm. In the present study, fabrics based on five different raw textiles having the same yarn count as well as the same weaving patterns were designed and created. Some of them were subjected to a coating process. The fabrics to be tested were as follows: coated with TiO2 nanoparticles, coated with SiO2 nanoparticles, coated fabric that does not contain bioceramic nanoparticle (BNFC), and non-coated fabrics (NCF). The structural characterization of the resulting samples was performed using scanning electron microscopy (SEM), abrasion tests, and air permeability. Following the structural characterization, the infrared emissivity properties were investigated using infrared thermography as well as attenuated total reflectance Fourier-transform infrared spectroscopy in the 8–14 IR range. According to the experimental findings, the fabrics coated with TiO2 and SiO2 displayed increased infrared emissivity values compared to the uncoated ones. In addition, it was observed that the use of bioceramic powders had no effect on air permeability and abrasion properties.

VEGETATION COVER MAPPING FROM RGB WEBCAM TIME SERIES FOR LAND SURFACE EMISSIVITY RETRIEVAL IN HIGH MOUNTAIN AREAS

Abstract. Land Surface Temperature (LST) products from thermal infrared imaging rely on information about the spatial distribution of Land Surface Emissivity (LSE). For portable, broadband thermal cameras for drone- or ground-based measurements with camera to object distances up to a few kilometres and with meter-scale resolution, threshold-based retrieval of LSE from Fractional green Vegetation Cover (FVC) can be used. As seasonal changes in vegetation LSE over the year cannot be accounted for by single satellite images or aerial orthophotos, this study evaluates an approach for FVC retrieval via permanently installed RGB webcams and derived Excess Green vegetation index (ExG) time series at a high-mountain test site in the European Alps. Daily ExG values were derived from the imagery of 27 days between 12/07/2021 and 30/10/2021 and projected to a 0.5 m Digital Surface Model (DSM). FVC reference data from 765 in-situ vegetation plots were used to assess the relationship between ExG and the vegetation cover and to determine the thresholds of ExG for no vegetation cover and full vegetation cover. Despite the bad correlation between ExG and in-field FVC with an R² score of 0.15, an approach using a well-tested orthophoto-retrieved NDVI for FVC retrieval performs just slightly better. The comparison of the remotely sensed data and the field measurements therefore remains complex. Time series analysis of both ExG and FVC for highly vegetated areas showed a significant decrease from summer to autumn, which reflects the seasonal changes of LSE for senescent vegetation. Calculated emissivities for vegetated pixels ranged from the minimum of 0.95 to the maximum of 0.985 over the season, while emissivity values for less vegetated pixels stayed constant during the season. The results of this study will be used as input to a correction model for remote LST measurements in the context of micro-scale investigations of the thermal niche of Alpine flora.

Study on the infrared emissivity of nonstoichiometric titanium chromium nitride films

Nonstoichiometric titanium chromium nitride (TiCrN) thin films with different nitrogen stoichiometric ratio were prepared by reactive magnetron co-sputtering. The nitrogen stoichiometric ratio was adjusted by change in the sputtering power. The phase compositions, morphology, adhesion force, resistivity and infrared emissivity were studied systematically. The results show that the adhesion force increased with increasing of the nitrogen stoichiometric ratio. The crystallinity was poor and the grain size was small when the nitrogen stoichiometric ratio was 0.35, leading to a great increase of resistivity and infrared emissivity of TiCrN film. When the nitrogen stoichiometric ratio was 0.44, the films crystallized and severe deformation of TiCrN crystal structure led to high resistivity and infrared emissivity. After the nitrogen stoichiometric ratio reached 0.58, serious deformation of TiCrN crystal weakened, and the combined effect of crystal deformation and carrier density caused the variation of the infrared emissivity. The infrared emissivity value of TiCrN film with nitrogen stoichiometric ratio of 0.58 was almost close to the value with nitrogen stoichiometric ratio of 0.81. Reduction of nitrogen stoichiometric ratio appropriately or decrease of crystal deformation in nonstoichiometric crystal TiCrN films was beneficial to reduce the infrared emissivity. The infrared emissivity of TiCrN films could be reduced to about 0.3.

Active thermo-reflectometry for absolute temperature measurement by infrared thermography on specular materials

Knowledge of material emissivity maps and their true temperatures is of great interest for contactless process monitoring and control with infrared cameras when strong heat transfer and temperature change are involved. This approach is always followed by emissivity or reflections issues. In this work, we describe the development of a contactless infrared imaging technique based on the pyro-reflectometry approach and a specular model of the material reflection in order to overcome emissivities and reflections problems. This approach enables in situ and real-time identification of emissivity fields and autocalibration of the radiative intensity leaving the sample by using a black body equivalent ratio. This is done to obtain the absolute temperature field of any specular material using the infrared wavelength. The presented set up works for both camera and pyrometer regardless of the spectral range. The proposed method is evaluated at room temperature with several heterogeneous samples covering a large range of emissivity values. From these emissivity fields, raw and heterogeneous measured radiative fluxes are transformed into complete absolute temperature fields.

Benefitting from Solar Energy Due to Different Emissivity Levels of Multiple Glass Windows for Buildings

In the study, firstly, heat transfer coefficients of windows were calculated according to the highest and lowest emissivity values. Secondly, monthly average solar radiation values were determined. The heat transfer coefficient calculated for double, triple and quadruple glass windows. Thirdly, the solar radiation in the south, north and east/west directions of the five climatic zones were multiplied by the shading factor, surface area and the solar energy factor of discrete buildings. Thus, the solar energy gain value for the heating period and solar energy losses for cooling period was determined. Finally, passive solar energy gains are calculated during the heating and cooling period for all climate zones. It has been calculated that in the fifth climatic zone in south direction, heat loss from windows with 0.05 emissivity can be provided with passive solar energy by 167.9% in double-glazed windows, 258.7% in triple-glazed windows and 349.1% in quadruple-glazed windows.

Study on the combustion behavior of single coal particle using a thermal-imaging technique

This study proposes a novel thermal-imaging detection technique that combines thermogravimetric analysis (TGA) with hyperspectral imaging to investigate the combustion behavior of single coal particles. The proposed technique enables the combustion reaction kinetics to be correlated with the observation of combustion regimes, as well as the combustion temperature and radiative parameters. The combustion behavior of two kinds of single coal particles, named Yinni (YN) and Datong (DT), is detected by the thermal-imaging technique. The results show that the single coal particles undergo a brief release of moisture/volatile, simultaneous combustion of volatile and char, and a relative long-term char oxidation during combustion. The combustion temperatures of the two single coal particles are approximately in the range of 750–1250 K, while the band-averaged emissivity values vary between 0.05 and 0.85. Furthermore, the simultaneous reaction rate, average temperature, and average emissivity of the two single coal particles during combustion are also obtained. It is found that the single coal particles follow a first-order reaction in the moisture/volatile release and char oxidation stages, and a complex reaction kinetics in the simultaneous combustion stage. The average temperature of the single coal particles is maintained at about 1000 K during the moisture/volatile release stage, but gradually increases during the simultaneous combustion and char oxidation stages. The average emissivity of the single coal particles keeps increasing in the release of moisture/volatile and simultaneous combustion stages, whereas remains basically unchanged in the long-term and slow char oxidation stage.

Detection of Radio Thermal Emission from the Kuiper Belt Object (486958) Arrokoth during the New Horizons Encounter

The New Horizons spacecraft encountered the Kuiper Belt object (KBO) Arrokoth (486958), originally designated as 2014 MU69 and formerly called “Ultima Thule,” on 2019 January 01. At 43.3 au from the Sun and 44.4 au from Earth, this was the most distant spacecraft reconnaissance of a solar system body to date. The Radio Science Experiment (REX) on New Horizons performed radiometry measurements of the KBO's thermal emission at λ = 4.2 cm in two observation slots, one before (dayside) and one after (nightside) the point of closest approach. Owing to the small size of the target, the intensity of the thermal emission was expected to be only marginally detectable. The KBO was not detected on approach because of unexpectedly large variations in the REX system temperature. A brightness temperature T b = 29 ± 5 K was derived for the nightside observation, considerably less than the predicted equilibrium temperature of ∼50 K derived for Arrokoth on the dayside. A model explaining this day−night contrast is used to constrain the global values of emissivity, thermal inertia, and electrical skin depth of the KBO. In particular, models with small values of thermal inertia and small values of electrical skin depth are excluded. Relatively high values of the effective radio emissivity (E eff > 0.8) provide better agreement with the REX observation.

Radiation heating test and development of porous MgAl2O4 ceramics with high thermal shielding effect based on Mie theory

AbstractPorous MgAl2O4 ceramics designated as THERMOSCATTTM have diffuse reflectance based on the Mie theory. The reflectance greatly suppresses radiation heat transfer and has low emissivity at 1–5 μm wavelengths. Their thermal conductivity has been measured as less than 0.3 W/(m K) at 1500°C. Furthermore, porous MgAl2O4 ceramics have near‐zero hemispherical spectral emissivity values at 0.35–5 μm wavelengths. High heat resistance and low emissivity materials in the atmosphere are useful for the innermost layer of industrial furnaces to confine energy efficiently. Additionally, this material is useful as a radiation reflectors, such as in stand‐off thermal protection systems. This study elucidated the suppression of radiation transfer in porous MgAl2O4 ceramics attributable to low thermal emissivity. Therefore, the thermal insulation performance under radiation heating in vacuum, the emissivity validity evaluation of low‐emissivity porous materials using finite element analysis, and microstructure effects on radiation heating performance and mechanical properties were investigated.

Assessment of Land Surface Temperature Estimates from Landsat 8-TIRS in A High-Contrast Semiarid Agroecosystem. Algorithms Intercomparison

Monitoring Land Surface Temperature (LST) from Landsat satellites has been shown to be effective in the estimation of crop water needs and modeling water use efficiency. Accurate LST estimation becomes critical in semiarid areas under water scarcity scenarios. This work shows the assessment of some well-known Single-Channel (SC) and Split-Window (SW) algorithms, adapted to Landsat 8/TIRS, under the conditions of a high-contrast semiarid agroecosystem. The recently released Landsat 8 Level-2 LST product (L8_ST) has also been included in the performance analysis. Ground measurements of surface temperature were taken for the evaluation during the summers of 2018–2019 in the cropland area of the Barrax test site, Spain. A dataset of 44 ground samples and 11 different L8/TIRS dates/scenes was gathered, covering a variety of crop fields and surface conditions. In addition, a simplified Single Band Atmospheric Correction (L-SBAC) was introduced based on a linearization of the atmospheric correction parameters with the water vapor content (w) and a redefinition of the emissivity threshold for the emissivity correction in the study site. The best results show differences within ±4.0 K for temperatures ranging 300–325 K. Statistics for the L-SBAC result in a RMSE of ±1.8 K with negligible systematic deviation. Similar results were obtained for the other SC and SW algorithms tested, whereas an overestimation of 1.0 K was observed for the L8_ST product because of inappropriate assignment of emissivity values. These results show the potential of the proposed linearization approach and set the uncertainty for LST estimates in high-contrast semiarid agroecosystems.

Methods for indirect measurements of the emissivity of tungsten and iron-carbon alloys

The purpose of the article is to increase accuracy and reliability of optical thermometry, including two-colour compensative thermometry with a priori averaged adjustment. The equation of nonlinearity of emissivity spectral distribution was previously obtained. The equation connects the nonlinearity coefficient of emissivity spectral distribution on the middle wave of the operating spectral range with the emissivity value at one of the boundary waves via 3 one-colour radiation temperatures. Based on the equation, linear two-range and parabolic methods for indirect measurements of emissivity is proposed. The results of emissivity determination are used to correct the a priori averaged adjustment of two-colour compensative thermometry.
 The linear method excludes the methodical error of temperature measurements for linear spectral distributions of emissivity. For tungsten and iron-carbon alloys, the methodical error of the two-colour compensative thermometry adjusted using the linear method does not exceed 0.52%. At the same time, the methodical errors of spectral ratio and energy pyrometry reach 3.19 and 6.07–8.42%. With a further hypothetical increase of nonlinearity coefficient by 2 times, the error of linear method increases from 0.52 to 1.02%. Both values are permissible in ferrous metallurgy.
 The two-range method is based on the inversion of nonlinearity of emissivity spectral distribution. The inversion means that nonlinearity coefficient changes its sign. In the case of tungsten, when spectral ranges are correctly chosen, the error of two-colour compensative thermometry with a corrected adjustment using the two-range method does not exceed the errors of reference measurements and makes up 0.06%.
 For essentially nonlinear distributions of emissivity, the parabolic method is proposed. The method excludes methodical error in case the emissivity on operating waves can be described by a polynomial of the 2-nd order. This polynomial approximation is typical for ferrous metals and their alloys. With the same nonlinearity of emissivity spectral distribution, for example, in case of tungsten, the error of parabolic method is 1.24 times less than of the linear method.