Distribution Of Thermal Radiation Research Articles

Motion estimation and spatial-temporal filter-based infrared small target detection algorithm

Under the effect of solar variation, atmospheric attenuation and thermal radiation distribution, the grey value of interference source is close to or equal to the target grey value. With the distance between the imaging system and the target being very long, the target is dotted or mottled in the image. In addition, the target motion is usually unknown and abrupt. All these factors cause the negative effect of small target detection. In this paper, we present a motion estimation and spatial-temporal filter-based algorithm to detect infrared small targets under complex background. The algorithm is divided into three steps: 1 researching the image transformation technology from greyscale pattern to entropy pattern; 2 studying the anisotropic smoothing and local constraint criterion of entropy flow; and 3 introducing spatial-temporal filter for detecting small targets through energy accumulation and trial search of targets. Compared to other methods, experimental results indicate that the proposed method can robustly detect small targets under complicated background.

New Type Cold Thermal Insulation Building Technology Based on BIM Virtual Technology

Due to the causes of the climate special in cold area, the design of building energy-saving insulation is highly targeted, therefore its research and analysis is suitable for the energy-saving design and method of the cold area construction, which has important significance for the construction energy-saving work in China. In this paper, BIM building information virtual construction technology is used, using BIM has software REVIT that carries out the structure design and thermal insulation design for the construction, establishing the different insulation function corresponding temperature increase and radiation heat related mathematical model. In order to verify the validity and reliability of the design model, this paper goes through the REVIT software for the building temperature light and heat radiation to carry on analog simulation, and then the temperature rise and thermal radiation distribution can be obtained by calculating, which provides a new computer method for the design of winter construction.

Recombination Properties of Diode Structures by Study of Thermal Emission Beyond the Fundamental Absorption Band

The study presents the possibilities of applying the measurement of spatial and temporal distribution of thermal radiation of a p-n junction structure located in a homogeneous temperature field higher than the ambient temperature, modulated by the presence of excess carriers injected through the junction, to determine surface recombination velocity at the injecting contact of the diode emitter and to measure the diffusion length in the base. Good agreement was obtained between the experimental results and calculations based on solutions of the transport equations.

Investigation on the Thermal Radiation Distribution of Oil Tank Fires

A thermal radiation monitoring system was established to measure the thermal radiation distribution of the crude oil tank fires, and the effect of open area, horizontal and vertical distance on the radiant heat flux was analyzed. The experimental results are compared with the calculated values by the point source model. It shows that the point source model have a high accuracy to calculate the radiant heat flux of the crude oil tank fire when the distance between the target point and the flame center is larger than the diameter of the tank.

Revisiting wildfires at the K‐Pg boundary

AbstractThe discovery of large amounts of soot in clays deposited at the Cretaceous‐Paleogene (K‐Pg) boundary and linked to the ~65 Ma Chicxulub impact crater led to the hypothesis that major wildfires were a consequence of the asteroid impact. Subsequently, several lines of evidence, including the lack of charcoal in North American sites, were used to argue against global wildfires. Close to the impact site fires are likely to be directly ignited by the impact fireball, whereas globally they could be ignited by radiation from the reentry of hypervelocity ejecta. To‐date, models of the latter have yet to take into account that ejection—and thus the emission of thermal radiation—is asymmetric and dependent on impact angle. Here, we model: (1) the impact and ejection of material, (2) the ballistic continuation of ejecta around a spherical Earth, and (3) the thermal pulse delivered to the Earth's surface when ejecta reenters the atmosphere. We find that thermal pulses in the downrange direction are sufficient to ignite flora several thousand kilometers from Chicxulub, whereas pulses at most sites in the uprange direction are too low to ignite even the most susceptible plant matter. Our analyses and models suggest some fires were ignited by the impact fireball and ejecta reentry, but that the nonuniform distribution of thermal radiation across the surface of the Earth is inconsistent with the ignition of fires globally as a direct and immediate result of the Chicxulub impact. Instead, we propose that the desiccation of flora by ejecta reentry, as well as the effects of postimpact global cooling/darkness, left much of the terrestrial flora prone to fires, and that the volume of soot in the global K‐Pg layer is explained by a combination of syn‐ and postimpact wildfires.

Distribution of Thermal Radiation Resulting From the Laser Diode into Biological Tissue

Tissue surface temperature distribution on the treatment site can serve as an indicator for the effectiveness of a photothermal therapy. In this paper, thermal effects of laser irradiance on biological tissue is investigated using finite difference (Euler forward method) to solve bioheat transfer equation, to find the temperature spread in the each layer of tissue in terms of depth and also to know the temperature distributed within a specified time. Numerical solution gives 2D and 3D simulation for temperature distribution during diode laser irradiation of tissue. By consider A cylindrical sample of biological tissue (tumor) irradiated by diode laser of wavelength 808 nm and power 1 w. optimal absorption coefficient was also identified to increase the effectiveness of heat treatment, this is done by inject the biological tissue with absorbent material to light or Photo sensitizer(as cardiogreen), temperatures were compared in terms of depth of tissue in tow cases : natural tissue and tissue injected by Photo sensitizer. These results can be used to control the laser treatment parameters and to optimize the treatment outcome.

Compressive Sensing for the Symmetry Distribution Analysis of Thermal Radiation on the Capsule inside a Cylindrical Hohlraum

The symmetric implosion of the pellet is very important in an inertial confinement fusion (ICF) system. The evaluation of symmetric distribution on the ICF pellet is time and memory consuming, especially when the elements of cylindrical hohlraums are iteratively subdivided. A novel compressive sensing (CS) based approach is presented in this paper to accurately valuate the distribution symmetry with much less computation. The core idea is that, the thermal radiation distribution is transformed in the spherical harmonic field, and the sparsity of spherical harmonics is accurately evaluated through CS approach. Finally, experiments are demonstrated to show higher efficiency of the proposed approach.

Origin of Molecular Outflow Determined from Thermal Dust Polarization

Abstract The observational expectation of polarization measurements of thermal dust radiation is investigated to find information on molecular outflows based on magnetohydrodynamical (MHD) and radiation-transfer simulations. There are two major proposed models for driving of molecular outflows: (1) molecular gas is accelerated by magnetic pressure gradient or magnetocentrifugal wind mechanism before the magnetic field and molecular gas are decoupled, (2) the linear momentum of a highly collimated jet is transferred to the ambient molecular gas. In order to distinguish between these two models, it is crucial to observe the configuration of the magnetic field. An observation of a toroidal magnetic field would be strong evidence that the first model is appropriate. We calculated the polarization distribution of thermal dust radiation due to the alignment of dust grains along the magnetic field using molecular outflow data obtained from two-dimensional axisymmetric MHD simulations. An asymmetric distribution around the $z$-axis is characteristic for magnetic fields composed of both poloidal and toroidal components. We found that the outflow has a low polarization degree compared with the envelope and that the envelope and outflow have different polarization directions (B-vector); i.e., the magnetic field within the envelope is parallel to the global magnetic field lines while the magnetic field of the outflow is perpendicular to it. We, then, demonstrated that the point-symmetric (rather than axisymmetric) distributions of low polarization regions indicate that molecular outflows are likely to be magnetically driven. Observations of this polarization distribution with tools such as ALMA would confirm the origin of the molecular outflow.

Infrared heater arrays for warming field plots scaled up to 5-m diameter

As Earth continues to warm globally, there is a need to conduct ecosystem plot warming experiments under conditions as representative of open fields in the future as possible. One promising approach is to use hexagonal arrays of infrared heaters such as described by [Kimball, B.A., Conley, M.M., Wang, S., Lin, X., Luo, C., Morgan, J., Smith, D., 2008. Infrared heater arrays for warming ecosystem field plots. Global Change Biology 14, 309–320]. However, their plots were only 3 m in diameter (7.1 m 2), which limits the stature of vegetation to shorter than about 1 m and also limits the amount of plant material that can destructively harvested. Therefore, we tested a larger hexagonal 5-m diameter array of infrared heaters, which provided a near tripling of useable area (19.6 m 2). The number of heaters was tripled from 6 to 18, and their height above the vegetative (wheat) canopy was scaled with the diameter (0.4 times diameter = 2.0 m). Distributions of down-going thermal radiation and of the resultant warming of the vegetation were quite uniform across the plot. Moreover, the same equation previously determined from 3-m diameter plots to describe the thermal radiation efficiency as a function of wind speed was still applicable. Thus, no problems were encountered in tripling the area of the infrared heater-warmed plots.

Quasiprobability distribution in a Kerr-nonlinear blackbody

In a Kerr-nonlinear blackbody, bare photons with opposite wave vectors and helicities are bound into pairs and unpaired photons are transformed into a new kind of quasiparticle, the nonpolariton. The nonpolariton system constitutes free thermal radiation in the blackbody. In this paper, the quasiprobability ( Q function) distribution of thermal radiation is investigated. Non-classical effects of quadrature squeezing have been observed. The structure of nonpolaritons is unsteady and governed by the temperature. The phase space of the photon system is considered and found that in the transition from the normal to the squeezed thermal radiation state, the phase symmetry of the photon system is spontaneously broken.

Thermometry based on the intensity distribution in a thermal-radiation spectrum

A modified method for temperature measurements based on thermal-radiation distribution is considered. A wide portion of the spectrum in the Wien region is recorded, and data are represented in the coordinate plane in which the Planck function is linearized. The temperature is determined from the slope of the straight line without invoking hypotheses about the emissivity. The direct observation of the distribution, of which the desired temperature is one parameter, allows the reliability and accuracy of determining the temperature to be improved. The temperature of reagents during a solid-phase exothermic chemical reaction has been determined using a spectrometer with a silicon CCD array sensitive in the range 200–850 nm.

Features of thermal radiation of plane-parallel semiconductor wafers

The spectra and angular distribution of thermal radiation from semitransparent plane-parallel semiconductor wafers are theoretically and experimentally investigated. It is shown that the spectrum of thermal radiation from these objects is oscillatory due to multiple-beam interference, and the radiation pattern has the lobes. The measurements are performed in the region of free-carrier absorption of n-GaAs and n-Si. It is concluded that the results of this study can be used for calculating new controlled IR-radiation sources.

Analytical axial view factors and thermal radiation distribution inside a cylindrical hohlraum

Thermal radiation redistribution inside a cylindrical hohlraum is discussed for uniform disc and two-ring sources. The flux conservation equation, coupled with self-similar scaling relation for the re-emitted flux, is solved to obtain the radiation temperature profile inside a gold capillary hohlraum at various times. The axial view factors required for the calculations are derived analytically in a closed form, which not only exactly reproduce the numerical results [G. D. Tsakiris, Phys. Fluids B 4, 992 (1992)] but also simplifies the overall problem enormously, both in terms of computational time and effort.

The Influence of Pressure on Soot Production and Radiation inTurbulent Kerosine Spray Flames

Detailed measurements of mixture fraction, flame temperature, soot volume fraction and spectrally resolved thermal radiation are reported in turbulent kerosine spray flames, burning at elevated temperatures and pressures (up to 13 bar). Flames are supported on an internal mixing, air-assist injector and confined within a cylindrical pressure vessel. Contrasting results, arising from the analysis of data on kerosine spray flames burning at various operating pressures, air-fuel ratios and fuel flow rates, are presented which provide new insight into the influence of operating pressure on soot formation and radiative heat transfer in practically relevant configurations. The experimental results between 1 and 13 bar suggest an underlying pressure dependence of the soot chemistry which is broadly linear. In addition, however, fuel atomisation and injector air-fuel ratio have a pronounced effect on the sooting propensity of the spray flames, which can be stronger than the influence of the operating pressure itself. They have a particularly strong influence on the rates of oxidative attack on soot particles and precursors and on the spectral distribution of thermal radiation between particulate and gaseous emissions. Continuum radiation from clouds of dispersed soot particles in the flame provides the major contribution to the total flame radiation in these comparatively fuel-rich kerosine spray flames with gas band radiation proving of only minor importance. The total radiation intensity from the flame then closely mirrors the trend in soot formation rates with respect to the dependence on operating conditions.

Measurement of the surface temperature distribution in the float zone of LiNbO 3

The thermal radiation emitted from a LiNbO 3 rod in a CO 2 laser-heated float-zone system has been measured by a two-dimensional thermal imaging radiometer with the spectral bandpass selected to be 3–5, 10.6 and 8–12 μm. When the float zone is formed, the interference of the monochromatic CO 2 laser with the thermal emission at the wavelengths of 10.6 and 8–12 μm can be minimized because the deformable gas-melt interface is optically smooth. The present results show that the emission of thermal radiation at the wavelengths of 10.6 and 8–12 μm is a surface phenomena, while that of 3–5 μm is a volumetric phenomena. The emission of thermal radiation in the 3–5 μm spectrum is used to determine the shape of the float-zone interface by using the method developed by Chen and Hu [J. Crystal Growth 149 (1995) 87]. Because the temperature at the gas-melt-solid interface is the melting point of the material, the emissivities for the wavelengths of 10.6 and 8–12 μm for the melting temperature can be obtained from the Planck radiation law, and they are around 0.92 and 0.98, respectively. Since the emissivity at these wavelengths is insensitive to the variation of the temperature, the surface temperature can be obtained from the thermal radiation distribution.

Method for measuring the intensity and spatial distribution of thermal radiation

Method for measuring the intensity and spatial distribution of thermal radiation

Spontaneous emission from a semi-bounded plasma

The electromagnetic radiation field of sources arbitrarily distributed throughout space is found for the case of a semi-bounded plasma when the charged plasma particles are specularly and randomly scattered by the plasma interface. The spectral distributions of the thermal radiation emitted by a nonisothermal semi-bounded plasma into an external medium having a nonzero temperature are calculated.

Thermal radiance observations of an active lava flow during the June 1984 eruption of Mount Etna

The thermal budget of an active lava flow observed on 20 June 1984 from the Southeast crater of Mount Etna, Sicily, Italy, was analyzed from data taken by the Landsat Thematic Mapper. The Thematic Mapper images constitute one of the few satellite data sets of sufficient spatial and spectral resolution to allow calibrated measurements on the distribution and intensity of thermal radiation from active lava flows. Using radiance data from two reflective infrared channels, we can estimate the temperature and areas of the hottest parts of the active flow, which correspond to hot (>500 °C) fractures or zones at the flow surface. Using this technique, we estimate that only 10%-20% of the total radiated thermal power output is emitted by hot zones or fractures, which constitute less than 1% of the observed surface area. Generally, it seems that only where hot fractures or zones constitute greater than about 1% of the surface area of the flow will losses from such features significantly reduce internal flow temperatures. Using our radiance observations as boundary conditions for a multicomponent thermal model of flow interior temperature, we infer that, for the parts of this flow subject to analysis, the boundary layer and flow thickness effects dominate over radiant zones in controlling the depression of core temperature.

Solar and thermal radiation in the Venus atmosphere

Attention is given to the solar and thermal radiation fields of Venus. Direct measurements and the results of numerical models based on direct measurements are presented. Radiation outside the atmosphere is considered with emphasis placed on global energy budget parameters, spectral and angular dependences, spatial distribution, and temporal variations of solar and thermal radiation. Radiation fluxes inside the atmosphere below 90 km are also considered with attention given to the solar flux at the surface, solar and thermal radiation fluxes from 100 km to the surface, and radiative heating and cooling below 100 km.

Meter-Wavelength Observations of Galactic Radio Sources and the Radiation from the Galactic Disk

view Abstract Citations (22) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Meter-Wavelength Observations of Galactic Radio Sources and the Radiation from the Galactic Disk Parrish, Alan Abstract The 1000-foot-diameter (305 m) radio telescope at the Arecibo Observatory has been used to observe the continuum emission of galactic sources at low radio frequencies. The following sources were observed: W49, W51, W56, NGC 1499, IC 410, NGC 2175, and NGC 2244. Observations were made at seven frequencies: 53, 65, 74, 89, 111, 196, and 318 MHz. Arrangements were made to obtain data on several of these frequencies simultaneously. densities of the observed sources are presented at the low frequencies. The data are also analyzed to obtain an estimate of the electron temperature of each thermal source, as well as the brightness tempera kure level of the nonthermal radiation in the line of sight to and beyond each source. The analysis procedu? using models of the sources to generate theoretical spectra for various values of two free par4meters: the electron temperature and the background brightness-temperature level. In performing the;analysis, convolution techniques were used to equalize the effects of different amounts of beam smoothing at different frequencies. Such techniques were especially helpful in analyzing data containing con tri\\ from nearby confusing sources. The derived electron-temperature results are sufficiently accurate to be compared with the results of recdtnbinatinn-line observations of NGC 2244. A range of pairs of permissible electron temperatures and background brightness-temperature levels is obtained for each of the other sources. Given this data, independent knowledge of the electron temperature of a source determines its associated background brightness-temperature level, and the latter result may be used in estimating the spatial distribution of the galactic non thermal radiation. Publication: The Astrophysical Journal Pub Date: May 1972 DOI: 10.1086/151466 Bibcode: 1972ApJ...174...33P full text sources ADS |