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Qiu, T. Q., J. P. Longtin, and C. L. Tien. "Characteristics of Radiation Absorption in Metallic Particles." Journal of Heat Transfer 117, no. 2 (May 1, 1995): 340–45. http://dx.doi.org/10.1115/1.2822527.
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Thermal radiation absorption in metallic particles is an important phenomenon in many contemporary laser-processing techniques, including laser cladding of coating materials and laser cleaning of particulate contaminations. In this work, the Drude free-electron theory and electromagnetic wave theory are utilized to characterize the internal absorption of CO2 laser radiation in aluminum, chromium, and nickel particles. The results show that metallic particles have unique radiation properties. Radiation absorption in large particles occurs only in a very narrow region of the front particle surface, which results in inefficient radiation absorption. On the other hand, micron and submicron particles can absorb radiation very efficiently, due to the strong diffraction effect at the particle surface. For extremely small particles (e.g., nanometer particles), radiation absorption becomes less efficient. The particle absorption efficiency is found to increase with temperature, and this temperature dependence can be determined from those of flat metal surfaces at the normal incidence.
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Parker, Robert G. "Particle radiation therapy." Cancer 55, S9 (May 1, 1985): 2240–45. http://dx.doi.org/10.1002/1097-0142(19850501)55:9+<2240::aid-cncr2820551429>3.0.co;2-f.
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Zhdankin, Vladimir, Dmitri A. Uzdensky, Gregory R. Werner, and Mitchell C. Begelman. "Kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling." Monthly Notices of the Royal Astronomical Society 493, no. 1 (January 31, 2020): 603–26. http://dx.doi.org/10.1093/mnras/staa284.
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ABSTRACT High-energy astrophysical systems frequently contain collision-less relativistic plasmas that are heated by turbulent cascades and cooled by emission of radiation. Understanding the nature of this radiative turbulence is a frontier of extreme plasma astrophysics. In this paper, we use particle-in-cell simulations to study the effects of external inverse Compton radiation on turbulence driven in an optically thin, relativistic pair plasma. We focus on the statistical steady state (where injected energy is balanced by radiated energy) and perform a parameter scan spanning from low magnetization to high magnetization (0.04 ≲ σ ≲ 11). We demonstrate that the global particle energy distributions are quasi-thermal in all simulations, with only a modest population of non-thermal energetic particles (extending the tail by a factor of ∼2). This indicates that non-thermal particle acceleration (observed in similar non-radiative simulations) is quenched by strong radiative cooling. The quasi-thermal energy distributions are well fit by analytic models in which stochastic particle acceleration (due to, e.g. second-order Fermi mechanism or gyroresonant interactions) is balanced by the radiation reaction force. Despite the efficient thermalization of the plasma, non-thermal energetic particles do make a conspicuous appearance in the anisotropy of the global momentum distribution as highly variable, intermittent beams (for high magnetization cases). The beamed high-energy particles are spatially coincident with intermittent current sheets, suggesting that localized magnetic reconnection may be a mechanism for kinetic beaming. This beaming phenomenon may explain rapid flares observed in various astrophysical systems (such as blazar jets, the Crab nebula, and Sagittarius A*).
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Chen, Huajun, Yitung Chen, Hsuan-Tsung Hsieh, and Nathan Siegel. "Computational Fluid Dynamics Modeling of Gas-Particle Flow Within a Solid-Particle Solar Receiver." Journal of Solar Energy Engineering 129, no. 2 (August 25, 2006): 160–70. http://dx.doi.org/10.1115/1.2716418.
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A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency.
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Otto, S., T. Trautmann, and M. Wendisch. "On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations." Atmospheric Chemistry and Physics Discussions 10, no. 11 (November 30, 2010): 29191–247. http://dx.doi.org/10.5194/acpd-10-29191-2010.
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Abstract. Realistic size equivalence and shape of Saharan mineral dust particles are derived from on in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10%. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5% at the TOA over ocean/land and 15% at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20%. Large dust particles significantly contribute to all the radiative effects reported.
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Wehner, B., and A. Wiedensohler. "Long term measurements of submicrometer urban aerosols: statistical analysis for correlations with meteorological conditions and trace gases." Atmospheric Chemistry and Physics Discussions 2, no. 5 (October 28, 2002): 1699–733. http://dx.doi.org/10.5194/acpd-2-1699-2002.
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Abstract. Long-term measurements (over 4 years) of particle number size distributions (submicrometer particles, 3--800 nm in diameter), trace gases (NO, NO2, and O3), and meteorological parameters (global radiation, wind speed and direction, atmospheric pressure, etc.) were taken in a moderately polluted site in the city of Leipzig (Germany). The resulting complex data set was analyzed with respect to seasonal, weekly, and diurnal variation of the submicrometer aerosol. Car traffic produced a peak in the number size distribution at around 30 nm particle diameter during morning rush hour on weekdays. A second peak at 10--15 nm particle diameter occurred around noon during summer, confirmed by high correlation between concentration of particles less than 20 nm and the global radiation. This new-particle formation at noon was correlated with the amount of global radiation. A high concentration of accumulation mode particles (between 100 and 800 nm), which are associated with large particle-surface area, might prevent this formation. Such high particle concentration in the ultrafine region (particles smaller than 20 nm in diameter) was not detected in the particle mass, and thus, particle mass concentration is not suitable for determining the diurnal patterns of particles. In summer, statistical time series analysis showed a cyclic pattern of ultrafine particles with a period of one day and confirmed the correlation with global radiation. Principal component analysis (PCA) revealed a strong correlation between the particle concentration for 20 -- 800 nm particles and the NO- and NO2-concentrations, indicating the influence of combustion processes on this broad size range, in particular during winter. In addition, PCA also revealed that particle concentration depended on meteorological conditions such as wind speed and wind direction, although the dependence differed with particle size class.
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Wehner, B., and A. Wiedensohler. "Long term measurements of submicrometer urban aerosols: statistical analysis for correlations with meteorological conditions and trace gases." Atmospheric Chemistry and Physics 3, no. 3 (June 24, 2003): 867–79. http://dx.doi.org/10.5194/acp-3-867-2003.
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Abstract. Long-term measurements (over 4 years) of particle number size distributions (submicrometer particles, 3-800 nm in diameter), trace gases (NO, NO2, and O3), and meteorological parameters (global radiation, wind speed and direction, atmospheric pressure, etc.) were taken in a moderately polluted site in the city of Leipzig (Germany). The resulting complex data set was analyzed with respect to seasonal, weekly, and diurnal variation of the submicrometer aerosol. Car traffic produced a peak in the number size distribution at around 20 nm particle diameter during morning rush hour on weekdays. A second peak at 10-15 nm particle diameter occurred around noon during summer, confirmed by high correlation between concentration of particles less than 20 nm and the global radiation. This new-particle formation at noon was correlated with the amount of global radiation. A high concentration of accumulation mode particles (between 100 and 800 nm), which are associated with large particle-surface area, might prevent this formation. Such high particle concentration in the ultrafine region (particles smaller than 20 nm in diameter) was not detected in the particle mass, and thus, particle mass concentration is not suitable for determining the diurnal patterns of particles. In summer, statistical time series analysis showed a cyclic pattern of ultrafine particles with a period of one day and confirmed the correlation with global radiation. Principal component analysis (PCA) revealed a strong correlation between the particle concentration for 20-800 nm particles and the NO- and NO2-concentrations, indicating the influence of combustion processes on this broad size range, in particular during winter. In addition, PCA also revealed that particle concentration depended on meteorological conditions such as wind speed and wind direction, although the dependence differed with particle size class.
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ULERY, JASON GLYNDWR. "THREE PARTICLE CORRELATIONS FROM STAR." International Journal of Modern Physics E 16, no. 10 (November 2007): 3123–30. http://dx.doi.org/10.1142/s0218301307009117.
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Two-particle correlations have shown modification to the away-side shape in central Au + Au collisions relative to pp , d + Au and peripheral Au + Au collisions. Different scenarios can explain this modification including: large angle gluon radiation, jets deflected by transverse flow, path length dependent energy loss, Cerenkov gluon radiation of fast moving particles, and conical flow generated by hydrodynamic Mach-cone shock-waves. Three-particle correlations have the power to distinguish the scenarios with conical emission, conical flow and Cerenkov radiation, from other scenarios. In addition, the dependence of the observed shapes on the pT of the associated particles can be used to distinguish conical emission from a sonic boom (Mach-cone) and from QCD-Čerenkov radiation. We present results from STAR on 3-particle azimuthal correlations for a high pT trigger particle with two softer particles. Results are shown for pp , d + Au and high statistics Au + Au collisions at [Formula: see text]. An important aspect of the analysis is the subtraction of combinatorial backgrounds. Systematic uncertainties due to this subtraction and the flow harmonics v2 and v4 are investigated in detail. The implications of the results for the presence or absence of conical flow from Mach-cones are discussed.
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Geer, Alan J., Peter Bauer, Katrin Lonitz, Vasileios Barlakas, Patrick Eriksson, Jana Mendrok, Amy Doherty, James Hocking, and Philippe Chambon. "Bulk hydrometeor optical properties for microwave and sub-millimetre radiative transfer in RTTOV-SCATT v13.0." Geoscientific Model Development 14, no. 12 (December 8, 2021): 7497–526. http://dx.doi.org/10.5194/gmd-14-7497-2021.
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Abstract. Satellite observations of radiation in the microwave and sub-millimetre spectral regions (broadly from 1 to 1000 GHz) can have strong sensitivity to cloud and precipitation particles in the atmosphere. These particles (known as hydrometeors) scatter, absorb, and emit radiation according to their mass, composition, shape, internal structure, and orientation. Hence, microwave and sub-millimetre observations have applications including weather forecasting, geophysical retrievals and model validation. To simulate these observations requires a scattering-capable radiative transfer model and an estimate of the bulk optical properties of the hydrometeors. This article describes the module used to integrate single-particle optical properties over a particle size distribution (PSD) to provide bulk optical properties for the Radiative Transfer for TOVS microwave and sub-millimetre scattering code, RTTOV-SCATT, a widely used fast model. Bulk optical properties can be derived from a range of particle models including Mie spheres (liquid and frozen) and non-spherical ice habits from the Liu and Atmospheric Radiative Transfer Simulator (ARTS) databases, which include pristine crystals, aggregates, and hail. The effects of different PSD and particle options on simulated brightness temperatures are explored, based on an analytical two-stream solution for a homogeneous cloud slab. The hydrometeor scattering “spectrum” below 1000 GHz is described, along with its sensitivities to particle composition (liquid or ice), size and shape. The optical behaviour of frozen particles changes in the frequencies above 200 GHz, moving towards an optically thick and emission-dominated regime more familiar from the infrared. This region is little explored but will soon be covered by the Ice Cloud Imager (ICI).
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Flamant, G., J. D. Lu, and B. Variot. "Radiation Heat Transfer in Fluidized Beds: A Comparison of Exact and Simplified Approaches." Journal of Heat Transfer 116, no. 3 (August 1, 1994): 652–59. http://dx.doi.org/10.1115/1.2910919.
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Radiation heat transfer at heat exchanger walls in fluidized beds has never been examined through a complete formulation of the problem. In this paper a wall-to-bed heat transfer model is proposed to account for particle convection, gas convection, and radiation exchange in a variable porosity medium. Momentum, energy, and intensity equations are solved in order to determine the velocity, temperature, radiative heat flux profiles and heat transfer coefficients. The discrete-ordinates method is used to compute the radiative intensity equation and the radiative flux divergence in the energy equation. Both the gray and the non-gray assumptions are considered, as well as dependent and independent scattering. The exact solution obtained is compared with several simplified approaches. Large differences are shown for small particles at high temperature but the simplified solutions are valid for large particle beds. The dependency of radiative contribution on controlling parameters is discussed.
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Poletaev, N. L. "The heating of a stream of particles by thermal counter radiation." Pozharovzryvobezopasnost/Fire and Explosion Safety 30, no. 2 (May 15, 2021): 15–22. http://dx.doi.org/10.22227/pvb.2021.30.02.15-22.
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Introduction. It is accepted that the depth of heating of the dust/gas/air mixture by the radiation of combustion products SR is equal to the length LR of the free path of radiation in the mixture. Numerical simulation of combustion of a gas-air mixture that has inert particles, taking into account the re-radiation of heat by heated particles of the fresh mixture, led to ratio SR >> LR. In this work, the analytical assessment of ratio χS = SR/LR is performed.One-dimensional problem model. The co-authors determined stationary temperature distribution over the flow of initially cold monodisperse particles suspended in vacuum. Particle velocity V is directed toward a heat-radiating, absolutely black surface that is permeable by particles. Simplifying assumptions are used: radiation consists of two oppositely-directed flows of electromagnetic energy; interaction between particles and radiation is described in the approximation of geometric optics; the temperature inside the particle is the same. Problem solving. It is shown that χS is determined by V=Vcp / (εT 0,5, σTb)3 , where cp, εT, σ, Tb are, respectively, heat capacity per unit volume of the suspended matter, integral emissivity of the particle material, the Stefan-Boltzmann constant, and the surface temperature. For ≤ 2.8, re-emission can be neglected: χS ≈ 1. At ≤ 1.2, temperature distribution regulates re-emission: χS ≈ 5 –1/(2 – εT) >> 1.Solution discussion. The analytical solution satisfactorily describes the available numerical solutions and experimental data for the case of combustion of a dust/gas/air mixture after specifying the parameters of a simplified model: the radiating surface should be understood as the flame front, Tb is the combustion temperature, and cp is the overall heat capacity of the mixture. The estimate ≤ 1.2 indicates the final high temperature of the gas suspension, the possibility of its autoignition far from the flame, and the need to change initial assumptions when simulating re-emission.Conclusions. Analytical evaluations make it possible to employ ratios SR >> LR and SR ≈ LR for the suspension over a thermal radiation source in vacuum. Conditions for the application of the results of simplified simulation of re-emission to the combustion of a dust/gas/air mixture are formulated.
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Klein, Hanna H., Rachamim Rubin, and Jacob Karni. "Generation of a Radiation Absorbing Medium for a Solar Receiver by Elutriation of Fine Particles From a Spouted Bed." Journal of Solar Energy Engineering 128, no. 3 (February 15, 2006): 406–8. http://dx.doi.org/10.1115/1.2212441.
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In high-temperature solar-thermal systems the conversion of solar to thermal energy requires a radiation absorbing surface to transfer the radiative solar energy to the working fluid. The present study focuses on the generation of a moving radiation absorber using particles suspended in the working fluid. Three methods of particle entrainment in a gas were investigated. Elutriating fine particles from a spouted bed was found to be the preferred method. The diameter range of the entrained carbon black particles was 0.030-25μm, with 99.7% of the particles having an equivalent diameter less than 1μm, and 48% of the projected surface area was due to agglomerated particles with average equivalent diameter >5μm. The moving radiation absorber was tested in a solar receiver using nitrogen as a working fluid. The inner wall temperatures in the receiver cavity were below the gas exit temperature, which shows that the bulk heat transfer from the incoming solar radiation to the gas takes place via the moving radiation absorbing particles.
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Kitzmann, D., A. B. C. Patzer, and H. Rauer. "On the Climatic Impact of CO2Ice Particles in Atmospheres of Terrestrial Exoplanets." Proceedings of the International Astronomical Union 8, S293 (August 2012): 303–8. http://dx.doi.org/10.1017/s1743921313013045.
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AbstractClouds play a significant role for the energy budget in planetary atmospheres. They can scatter incident stellar radiation back to space, effectively cooling the surface of terrestrial planets. On the other hand, they may contribute to the atmospheric greenhouse effect by trapping outgoing thermal radiation. For exoplanets near the outer boundary of the habitable zone, condensation of CO2can occur due to the low atmospheric temperatures. These CO2ice clouds may play an important role for the surface temperature and, therefore, for the question of habitability of those planets. However, the optical properties of CO2ice crystals differ significantly from those of water droplets or water ice particles. Except for a small number of strong absorption bands, they are almost transparent with respect to absorption. Instead, they are highly effective scatterers at long and short wavelengths. Therefore, the climatic effect of a CO2ice cloud will depend on how much incident stellar radiation is scattered to space in comparison to the amount of thermal radiation scattered back towards the planetary surface. This contribution aims at the potential greenhouse effect of CO2ice particles. Their scattering and absorption properties are calculated for assumed particle size distributions with different effective radii and particle densities. An accurate radiative transfer model is used to determine the atmospheric radiation field affected by such CO2particles. These results are compared to less detailed radiative transfer schemes employed in previous studies.
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Miyahara, Nobuyuki, Tatuaki Kanai, and Masahiro Endo. "Particle beam radiation therapy." Proceedings of the JSME Bioengineering Conference and Seminar 2000.11 (2000): 127–28. http://dx.doi.org/10.1299/jsmebs.2000.11.0_127.
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Karlsson, Erik. "Detectors for particle radiation." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 270, no. 2-3 (July 1988): 604. http://dx.doi.org/10.1016/0168-9002(88)90737-1.
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More, Richard, Frank Graziani, Jim Glosli, and Michael Surh. "Radiation in particle simulations." High Energy Density Physics 6, no. 1 (January 2010): 29–38. http://dx.doi.org/10.1016/j.hedp.2009.07.002.
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Slater, James M. "Considerations in Identifying Optimal Particles for Radiation Medicine." Technology in Cancer Research & Treatment 5, no. 2 (April 2006): 73–79. http://dx.doi.org/10.1177/153303460600500201.
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Of the many ionizing particles discovered so far, only a few are reasonable to consider for radiation therapy. These include photons, protons, neutrons, electrons, mesons, antiprotons, and ions heavier than hydrogen. Most of these particles are used therapeutically to destroy or inactivate malignant and sometimes benign cells. Since the late 1930s, accelerators have been developed that have expanded radiation oncologists' abilities to produce various ionizing particle beams. Over the past decade, radiation oncologists have become increasingly interested in pursuing particles other than the conventional photons that have been used almost exclusively since X-rays were discovered in 1895. Physicians recognize that normal-tissue morbidity from all forms of anti-cancer treatment is the primary factor limiting the success of those treatments. In radiation therapy, all particles mentioned above can destroy any cancer cell; controlling the beam in three dimensions, thus providing the physician with the capability of avoiding normal-tissue injury, is the fundamental deficiency in the use of X-rays (photons). Heavy charged particles possess near-ideal characteristics for exercising control in three dimensions; their primary differences are due to the number of protons contained within their nuclei. As their number of protons increase (atomic number) their ionization density (LET) increases. In selecting the optimal particle for therapy from among the heavy charged particles, one must carefully consider the ionization density created by each specific particle. Ionization density creates both advantages and disadvantages for patient treatment; these factors must be matched with the patients' precise clinical needs. The current state of the art involves studying the clinical advantages and disadvantages of the lightest ion, the proton, as compared to other particles used or contemplated for use. Full analysis must await adequate data developed from long-term studies to determine the precise role of each potential particle for human use. It is expected that one particle beam will emerge as the mainstream for treating human disease, and a small number of particles may emerge in an adjunctive role.
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Wang, K. Y., and W. W. Yuen. "Rapid Heating of Gas/Small Particle Mixture." Journal of Solar Energy Engineering 109, no. 2 (May 1, 1987): 143–49. http://dx.doi.org/10.1115/1.3268191.
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The concept of using a mixture of particles and air as a medium to absorb radiative energy has been proposed for various applications. In this paper, carbon particles mixed with gas form a medium that absorbs radiation from sources such as concentrated solar energy. A single-particle, two-temperature model is used to study the transient temperature of the particle/gas mixture as it undergoes a constant pressure expansion process. The results indicate that for particles smaller than 1 μm in diameter, the surrounding air can be heated as quickly as the particles, while for particles larger than 1 mm in diameter, the air temperature stays relatively unchanged and the particles are heated to a very high temperature. The scattering albedos from the particles are also calculated, revealing that their contribution from scattering to the heating process is insignificant for particles with diameter less than 1 μm.
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Ran, Jing, Ping Zhang, Wei Zhong Yang, Da Li Zhou, Heng Liu, and Zhe Li. "Preparation and Properties of Zinc Oxide and Titanium Oxide Ultra-Fine Composite Particles for Attenuation of Ultraviolet Radiation." Key Engineering Materials 336-338 (April 2007): 822–25. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.822.
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A co-precipitation preparation method and the properties of an ultraviolet (UV)-attenuating agent are described in this paper. The composite particles of ultra-fine zinc oxide and titanium oxide are used to attenuate UV radiation. Preparation of TiOSO4, ZnCl2 solution and the co-precipitation of the composite particles by alkali are included during the process. Various types of surfactants have been used to modify the composite particles. Particle sizes are determined by laser particle analyzer, and reflectance and absorption coefficient are determined by UV-VIS spectrophotometer. Results show that particle size of the composite particles as well as total reflectance and absorption coefficient depend on the surfactants, pH value, and carline temperature. The average sizes of zinc oxide and titanium oxide ultra-fine particles range from39 to 65 nm. Attenuation capability of ultraviolet radiation becomes stronger when the particle average sizes becomes smaller. Composites less than 40 nm with titanium oxide of rutile phase attenuate most effectively the ultraviolet radiation ranging from 280 nm to 390 nm.
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Jayaprakash Mishra and Tumbanath Samantara. "Study of Unsteady Two Phase Flow over An Inclined Permeable Stretching Sheet with Effects of Electrification and Radiation." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 97, no. 2 (August 31, 2022): 26–38. http://dx.doi.org/10.37934/arfmts.97.2.2638.
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An analysis on flow and heat transfer with in a two-dimensional unsteady radiative boundary layer with fluid-particle interaction has been studied. The flow is occurred due to the suddenly linear movement of an inclined permeable stretching sheet. The flow is considered in a neutral medium where no external electric or magnetic field is supplied. But due to the random motion of particles leads to interaction between fluid-particle, particle-particle and particle-wall, a tribo-electric effect occurs. As a result, both the fluid as well as particles are electrified which creates a major impact on flow field. Hence, a balanced mathematical model has been formulated considering both electrification and radiation parameter on both the phases. Using similarity transformation, the governing equations are transferred to ODEs and solved by built in solver Bvp4c of MATLAB. The impacts of various parameters on the flow field have been discussed and determined the heat transfer characteristics. The stronger electric filed significantly enhances the temperature of both fluid and particle phase, which occurs more heat transfer on the surface.
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Otto, S., T. Trautmann, and M. Wendisch. "On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations." Atmospheric Chemistry and Physics 11, no. 9 (May 12, 2011): 4469–90. http://dx.doi.org/10.5194/acp-11-4469-2011.
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Abstract. Realistic size equivalence and shape of Saharan mineral dust particles are derived from in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10 %. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20 %. Large dust particles significantly contribute to all the radiative effects reported. They strongly enhance the absorbing properties and forward scattering in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land.
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Uvarova, Lyudmila A., Irina V. Krivenko, Marina A. Smirnova, and Alexey B. Nadykto. "Electromagnetic Radiation and Heat Transfer in Disperse Systems Consisting of Spherical and Cylindrical Particles." EPJ Web of Conferences 224 (2019): 02008. http://dx.doi.org/10.1051/epjconf/201922402008.
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The article deals with the electromagnetic radiation transfer in systems of spherical disperse particles with different optical characteristics. A model of the electromagnetic radiation transfer in cylindrical particles containing a small volume of different chemical substance is developed. The substance differs substantially from that of the particle in a radiation absorption coefficient for the wavelength under study in the long wave approximation. The finite element method is used to calculate the temperature field for the system of spherical particles in a two-dimensional approximation. The configurations of particle packing is chosen on a random basis, which significantly complicated the calculations, the longitudinal and transverse diameters of particle clusters, the distance between centers of two largest particles, and similar natural geometric properties have been considered as characteristic system dimensions.The possibility of controlling heat transfer in such systems is studied. It follows from our model calculations that both electromagnetic and thermal interaction of dispersed particles can be noticeable at large distances between their centers; that near the boundary of the dispersed particle there is a thermal surface layer of the particle, where the temperature distribution is essentially heterogeneous. It is concluded that the thermal mechanism of destruction of a weakly absorbing particle due to a strong increase in temperature because of electromagnetic resonance in a neighboring particle with a strong absorption. It is established that the effect of collective influences in polydisperse system can change temperature by more than 1,5 times.
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Bagrov, Vladislav, Anna Kasatkina, and Alexey Pecheritsyn. "Effective Angle of Synchrotron Radiation." Symmetry 12, no. 7 (July 2, 2020): 1095. http://dx.doi.org/10.3390/sym12071095.
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An exact analytical expression for the effective angle is determined for an arbitrary energy value of a radiating particle. An effective angle of instantaneous power is defined for synchrotron radiation in the framework of classical electrodynamics. This definition explicitly contains the most symmetric distribution of half the total of the instantaneous power of synchrotron radiation. Two exact analytical expressions for the effective angle are considered for the arbitrary energy values of a radiating particle, and the second expression brings to light the exact asymptotics of the effective angle in the ultrarelativistic limit.
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Blakely, Eleanor A. "The 20th Gray lecture 2019: health and heavy ions." British Journal of Radiology 93, no. 1115 (November 1, 2020): 20200172. http://dx.doi.org/10.1259/bjr.20200172.
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Objective Particle radiobiology has contributed new understanding of radiation safety and underlying mechanisms of action to radiation oncology for the treatment of cancer, and to planning of radiation protection for space travel. This manuscript will highlight the significance of precise physical and biologically effective dosimetry to this translational research for the benefit of human health. This review provides a brief snapshot of the evolving scientific basis for, and the complex current global status, and remaining challenges of hadron therapy for the treatment of cancer. The need for particle radiobiology for risk planning in return missions to the Moon, and exploratory deep-space missions to Mars and beyond are also discussed. Methods Key lessons learned are summarized from an impressive collective literature published by an international cadre of multidisciplinary experts in particle physics, radiation chemistry, medical physics of imaging and treatment planning, molecular, cellular, tissue radiobiology, biology of microgravity and other stressors, theoretical modeling of biophysical data, and clinical results with accelerator-produced particle beams. Results Research pioneers, many of whom were Nobel laureates, led the world in the discovery of ionizing radiations originating from the Earth and the Cosmos. Six radiation pioneers led the way to hadron therapy and the study of charged particles encountered in outer space travel. Worldwide about 250,000 patients have been treated for cancer, or other lesions such as arteriovenous malformations in the brain between 1954 and 2019 with charged particle radiotherapy, also known as hadron therapy. The majority of these patients (213,000) were treated with proton beams, but approximately 32,000 were treated with carbon ion radiotherapy. There are 3500 patients who have been treated with helium, pions, neon or other ions. There are currently 82 facilities operating to provide ion beam clinical treatments. Of these, only 13 facilities located in Asia and Europe are providing carbon ion beams for preclinical, clinical, and space research. There are also numerous particle physics accelerators worldwide capable of producing ion beams for research, but not currently focused on treating patients with ion beam therapy but are potentially available for preclinical and space research. Approximately, more than 550 individuals have traveled into Lower Earth Orbit (LEO) and beyond and returned to Earth. Conclusion Charged particle therapy with controlled beams of protons and carbon ions have significantly impacted targeted cancer therapy, eradicated tumors while sparing normal tissue toxicities, and reduced human suffering. These modalities still require further optimization and technical refinements to reduce cost but should be made available to everyone in need worldwide. The exploration of our Universe in space travel poses the potential risk of exposure to uncontrolled charged particles. However, approaches to shield and provide countermeasures to these potential radiation hazards in LEO have allowed an amazing number of discoveries currently without significant life-threatening medical consequences. More basic research with components of the Galactic Cosmic Radiation field are still required to assure safety involving space radiations and combined stressors with microgravity for exploratory deep space travel. Advances in knowledge The collective knowledge garnered from the wealth of available published evidence obtained prior to particle radiation therapy, or to space flight, and the additional data gleaned from implementing both endeavors has provided many opportunities for heavy ions to promote human health.
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Chen, Bingbing. "Study on Tunnelling Radiation in 4 Dimension Black Holes Vector Particles." Journal of Physics: Conference Series 2083, no. 2 (November 1, 2021): 022110. http://dx.doi.org/10.1088/1742-6596/2083/2/022110.
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Abstract Recent studies show that the tunnelling radiation of vector particles has been studied successfully by WKB approximation and Hamilton-Jacobi method. In view of this, the main purpose of this paper is to study the Proca equation and the vector particles tunnelling radiation in a 4-dimensional black hole. Finally, the results here show that the temperature of the vector particle is the same as that of the Dirac particle.
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Reinhardt, B., R. Buras, L. Bugliaro, S. Wilbert, and B. Mayer. "Determination of circumsolar radiation from Meteosat Second Generation." Atmospheric Measurement Techniques 7, no. 3 (March 31, 2014): 823–38. http://dx.doi.org/10.5194/amt-7-823-2014.
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Abstract. Reliable data on circumsolar radiation, which is caused by scattering of sunlight by cloud or aerosol particles, is becoming more and more important for the resource assessment and design of concentrating solar technologies (CSTs). However, measuring circumsolar radiation is demanding and only very limited data sets are available. As a step to bridge this gap, a method was developed which allows for determination of circumsolar radiation from cirrus cloud properties retrieved by the geostationary satellites of the Meteosat Second Generation (MSG) family. The method takes output from the COCS algorithm to generate a cirrus mask from MSG data and then uses the retrieval algorithm APICS to obtain the optical thickness and the effective radius of the detected cirrus, which in turn are used to determine the circumsolar radiation from a pre-calculated look-up table. The look-up table was generated from extensive calculations using a specifically adjusted version of the Monte Carlo radiative transfer model MYSTIC and by developing a fast yet precise parameterization. APICS was also improved such that it determines the surface albedo, which is needed for the cloud property retrieval, in a self-consistent way instead of using external data. Furthermore, it was extended to consider new ice particle shapes to allow for an uncertainty analysis concerning this parameter. We found that the nescience of the ice particle shape leads to an uncertainty of up to 50%. A validation with 1 yr of ground-based measurements shows, however, that the frequency distribution of the circumsolar radiation can be well characterized with typical ice particle shape mixtures, which feature either smooth or severely roughened particle surfaces. However, when comparing instantaneous values, timing and amplitude errors become evident. For the circumsolar ratio (CSR) this is reflected in a mean absolute deviation (MAD) of 0.11 for both employed particle shape mixtures, and a bias of 4 and 11%, for the mixture with smooth and roughend particles, respectively. If measurements with sub-scale cumulus clouds within the relevant satellite pixels are manually excluded, the instantaneous agreement between satellite and ground measurements improves. For a 2-monthly time series, for which a manual screening of all-sky images was performed, MAD values of 0.08 and 0.07 were obtained for the two employed ice particle mixtures, respectively.
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Kryvdyk, Volodymyr. "Radiation Bursts from a Presupernova Collapsar." International Astronomical Union Colloquium 192 (2005): 215–18. http://dx.doi.org/10.1017/s0252921100009210.
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SummaryThe radiation from the magnetic presupernova star is calculated. This radiation will generate when the magnetosphere of presupernova star compresses during collapse and its magnetic field increases considerably. The variable magnetic field will accelerate the charged particle, which generate radiation when moving in the magnetic field. The particles dynamics and their non-thermal emission in the magnetospheres of presupernova collapsing star with initial dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere are considered. The radiation flux depend on the distance to the star, its magnetic field, and the particle spectrum in the magnetosphere. This flux can be observed by means of modern instruments in broad band (from radio waves to gamma rays). The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of radiation bursts with duration equal to the stellar collapse time.
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Bespalov, P. A., V. V. Zaitsev, and A. V. Stepanov. "Energetic Particles in a Flare Loop: Spectra and Radiation Signatures." Symposium - International Astronomical Union 142 (1990): 421–27. http://dx.doi.org/10.1017/s0074180900088343.
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It has been shown that high energy particle spectra, particle dynamics, and radiation in a flare loop are determined by wave-particle interactions. The electron-whistler interaction occurs under conditions of strong pitch angle diffusion that makes the particle distribution function isotropic. The flare loop electrons retain information about the particle source spectrum. The interaction of energetic ions with Alfven waves is characterized by strong, moderate, and weak diffusion. The time delays in hard X-ray and gamma-ray emission during one-step acceleration processes might be understood in terms of a trap-plus-turbulent propagation model. The density of precipitating particles is less than or equal to the trapping one. Radiation signatures of flare loop electrons are discussed.
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Vergara-Temprado, Jesús, Annette K. Miltenberger, Kalli Furtado, Daniel P. Grosvenor, Ben J. Shipway, Adrian A. Hill, Jonathan M. Wilkinson, Paul R. Field, Benjamin J. Murray, and Ken S. Carslaw. "Strong control of Southern Ocean cloud reflectivity by ice-nucleating particles." Proceedings of the National Academy of Sciences 115, no. 11 (February 28, 2018): 2687–92. http://dx.doi.org/10.1073/pnas.1721627115.
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Large biases in climate model simulations of cloud radiative properties over the Southern Ocean cause large errors in modeled sea surface temperatures, atmospheric circulation, and climate sensitivity. Here, we combine cloud-resolving model simulations with estimates of the concentration of ice-nucleating particles in this region to show that our simulated Southern Ocean clouds reflect far more radiation than predicted by global models, in agreement with satellite observations. Specifically, we show that the clouds that are most sensitive to the concentration of ice-nucleating particles are low-level mixed-phase clouds in the cold sectors of extratropical cyclones, which have previously been identified as a main contributor to the Southern Ocean radiation bias. The very low ice-nucleating particle concentrations that prevail over the Southern Ocean strongly suppress cloud droplet freezing, reduce precipitation, and enhance cloud reflectivity. The results help explain why a strong radiation bias occurs mainly in this remote region away from major sources of ice-nucleating particles. The results present a substantial challenge to climate models to be able to simulate realistic ice-nucleating particle concentrations and their effects under specific meteorological conditions.
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Durant, Adam J., Sandy P. Harrison, I. Matthew Watson, and Y. Balkanski. "Sensitivity of direct radiative forcing by mineral dust to particle characteristics." Progress in Physical Geography: Earth and Environment 33, no. 1 (February 2009): 80–102. http://dx.doi.org/10.1177/0309133309105034.
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Airborne dust affects the Earth's energy balance — an impact that is measured in terms of the implied change in net radiation (or radiative forcing, in W m-2) at the top of the atmosphere. There remains considerable uncertainty in the magnitude and sign of direct forcing by airborne dust under current climate. Much of this uncertainty stems from simplified assumptions about mineral dust-particle size, composition and shape, which are applied in remote sensing retrievals of dust characteristics and dust-cycle models. Improved estimates of direct radiative forcing by dust will require improved characterization of the spatial variability in particle characteristics to provide reliable information dust optical properties. This includes constraints on: (1) particle-size distribution, including discrimination of particle subpopulations and quantification of the amount of dust in the sub-10 µm to <0.1 µm mass fraction; (2) particle composition, specifically the abundance of iron oxides, and whether particles consist of single or multi-mineral grains; (3) particle shape, including degree of sphericity and surface roughness, as a function of size and mineralogy; and (4) the degree to which dust particles are aggregated together. The use of techniques that measure the size, composition and shape of individual particles will provide a better basis for optical modelling.
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Guevara Vasquez, Fernando, and China Mauck. "Periodic particle arrangements using standing acoustic waves." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2232 (December 2019): 20190574. http://dx.doi.org/10.1098/rspa.2019.0574.
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We determine crystal-like materials that can be fabricated by using a standing acoustic wave to arrange small particles in a non-viscous liquid resin, which is cured afterwards to keep the particles in the desired locations. For identical spherical particles with the same physical properties and small compared to the wavelength, the locations where the particles are trapped correspond to the minima of an acoustic radiation potential which describes the net forces that a particle is subject to. We show that the global minima of spatially periodic acoustic radiation potentials can be predicted by the eigenspace of a small real symmetric matrix corresponding to its smallest eigenvalue. We relate symmetries of this eigenspace to particle arrangements composed of points, lines or planes. Since waves are used to generate the particle arrangements, the arrangement’s periodicity is limited to certain Bravais lattice classes that we enumerate in two and three dimensions.
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Pörtner, Lukas, Ying Gu, and Martin Schiemann. "Investigation of Pulverized Biomass and Coal Char Emissivity." Energies 13, no. 18 (September 5, 2020): 4620. http://dx.doi.org/10.3390/en13184620.
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Current work presents an optical setup, its calibration and reference process and the first results from single particle emissivity measurements of pulverized biomass and coal fuel particles. In contrast to earlier attempts, the setup offers the possibility of emissivity measurements during the whole particle burn-off. A laser ignites a single particle, placed in the center of the setup. Two photomultipliers observe the emitted particle radiation in the visible range (550 nm and 700 nm) for temperature calculation, using two-color pyrometry. An InSb-detector records the emitted particle radiation between 2.4 µm and 5.5 µm, which is later used to calculate particle emissivity in this range. The conclusion of multiple particle measurements lead to decreasing particle emissivity with increasing temperature. For coal particles the emissivity decreases from 0.45 at 2300 K to 0.03 at 3400 K. Biomass char shows a similar trend with a decrease from 0.18 (2100 K) to 0.03 (2900 K).
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Guo, Zhixiong, and Shigenao Maruyama. "Prediction of Radiative Heat Transfer in Industrial Equipment Using the Radiation Element Method." Journal of Pressure Vessel Technology 123, no. 4 (May 23, 2001): 530–36. http://dx.doi.org/10.1115/1.1388235.
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The radiation element method by ray emission method, REM2, has been formulated to predict radiative heat transfer in three-dimensional arbitrary participating media with nongray and anisotropically scattering properties surrounded by opaque surfaces. To validate the method, benchmark comparisons were conducted against the existing several radiation methods in a rectangular three-dimensional media composed of a gas mixture of carbon dioxide and nitrogen and suspended carbon particles. Good agreements between the present method and the Monte Carlo method were found with several particle density variations, in which participating media of optical thin, medium, and thick were included. As a numerical example, the present method is applied to predict radiative heat transfer in a boiler model with nonisothermal combustion gas and carbon particles and diffuse surface wall. Elsasser narrow-band model as well as exponential wide-band model is adopted to consider the spectral character of CO2 and H2O gases. The distributions of heat flux and heat flux divergence in the boiler furnace are obtained. The difference of results between narrow-band and wide-band models is discussed. The effects of gas model, particle density, and anisotropic scattering are scrutinized.
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Zhang, Shenyi, Robert F. Wimmer-Schweingruber, Jia Yu, Chi Wang, Qiang Fu, Yongliao Zou, Yueqiang Sun, et al. "First measurements of the radiation dose on the lunar surface." Science Advances 6, no. 39 (September 2020): eaaz1334. http://dx.doi.org/10.1126/sciadv.aaz1334.
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Human exploration of the Moon is associated with substantial risks to astronauts from space radiation. On the surface of the Moon, this consists of the chronic exposure to galactic cosmic rays and sporadic solar particle events. The interaction of this radiation field with the lunar soil leads to a third component that consists of neutral particles, i.e., neutrons and gamma radiation. The Lunar Lander Neutrons and Dosimetry experiment aboard China’s Chang’E 4 lander has made the first ever measurements of the radiation exposure to both charged and neutral particles on the lunar surface. We measured an average total absorbed dose rate in silicon of 13.2 ± 1 μGy/hour and a neutral particle dose rate of 3.1 ± 0.5 μGy/hour.
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Granja, C., J. Jakubek, P. Soukup, M. Jakubek, D. Turecek, L. Marek, S. Polansky, et al. "Spectral and directional sensitive composition characterization of mixed-radiation fields with the miniaturized radiation camera MiniPIX Timepix2." Journal of Instrumentation 17, no. 11 (November 1, 2022): C11014. http://dx.doi.org/10.1088/1748-0221/17/11/c11014.
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Abstract The semiconductor pixel detector Timepix2 is operated with highly integrated readout electronics as a miniaturized and portable MiniPIX TPX2 radiation camera for radiation imaging and spectral-sensitive particle tracking in wide field-of-view. The device provides room-temperature operation, ease of use (single USB 2.0 port), online response with single track visualization, fast frame readout (up to 60 fps) and double per-pixel response for detailed measurements with per-pixel energy and counting or energy and timing sensitivity. We evaluate the response and applicability of a MiniPIX TPX2 camera with the Timepix2 ASIC chip equipped with a 300 µm thick silicon sensor for wide-range composition and spectral characterization of mixed-radiation fields. Measurements were performed in high-energy proton radiotherapy environments with protons of selected energies in the range 225–70 MeV and water-equivalent targets of varying configuration (size, dimension, geometry). High-resolution pattern recognition and spectral-tracking analysis of the single particle tracks in the pixelated detector enable to resolve and classify all detected signals according particle species, direction and energy loss. Based on the experimental calibrations performed with well-defined radiation fields together with quantum imaging visualization of single particle tracks, ten broad-range particle-event classes are resolved. Mixed-radiation fields are thus analyzed according particle-event types in wide range of deposited energy, linear-energy-transfer LET, particle fluxes and dose rates. The spatial distribution over the detector sensor matrix of the distinguished groups can be visualized as well as the directional mapping of energetic charged particles.
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Bingham, R. "Particle acceleration by electromagnetic waves." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1871 (January 24, 2008): 1749–56. http://dx.doi.org/10.1098/rsta.2007.2183.
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We consider the symmetry in the interaction of photons and electrons, which has led to a common description of electron and photon accelerations; effects such as photon Landau damping arise naturally from such a treatment. Intense electromagnetic waves can act as a photon mirror to charged particles. The subsequent acceleration is equivalent to the photon pulse accelerating electrons. During the interaction or reflection process, the charged particle can emit bursts of radiation similar to the radiation emitted from the particles during wave breaking of plasma waves.
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KOROL, ANDREI V., ANDREY V. SOLOV'YOV, and WALTER GREINER. "TOTAL ENERGY LOSSES DUE TO THE RADIATION IN AN ACOUSTICALLY BASED UNDULATOR: THE UNDULATOR AND THE CHANNELING RADIATION INCLUDED." International Journal of Modern Physics E 09, no. 01 (February 2000): 77–105. http://dx.doi.org/10.1142/s0218301300000064.
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This paper is devoted to the investigation of the radiation energy losses of an ultra-relativistic charged particle channeling along a crystal plane which is periodically bent by a transverse acoustic wave. In such a system there are two essential mechanisms leading to the photon emission. The first one is the ordinary channeling radiation. This radiation is generated as a result of the transverse oscillatory motion of the particle in the channel. The second one is the acoustically induced radiation. This radiation is emitted because of the periodic bending of the particle's trajectory created by the acoustic wave. The general formalism described in our work is applicable for the calculation of the total radiative losses accounting for the contributions of both radiation mechanisms. We analyze the relative importance of the two mechanisms at various amplitudes and lengths of the acoustic wave and the energy of the projectile particle. We establish the ranges of projectile particle energies, in which total energy loss is small for the LiH, C, Si, Ge, Fe and W crystals. This result is important for the determination of the projectile particle energy region, in which acoustically induced radiation of the undulator type and also the stimulated photon emission can be effectively generated. The latter effects have been described in our previous works.
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Nachbar, Mario, Henrike Wilms, Denis Duft, Tasha Aylett, Kensei Kitajima, Takuya Majima, John M. C. Plane, Markus Rapp, and Thomas Leisner. "The impact of solar radiation on polar mesospheric ice particle formation." Atmospheric Chemistry and Physics 19, no. 7 (April 3, 2019): 4311–22. http://dx.doi.org/10.5194/acp-19-4311-2019.
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Abstract. Mean temperatures in the polar summer mesopause can drop to 130 K. The low temperatures in combination with water vapor mixing ratios of a few parts per million give rise to the formation of ice particles. These ice particles may be observed as polar mesospheric clouds. Mesospheric ice cloud formation is believed to initiate heterogeneously on small aerosol particles (r<2 nm) composed of recondensed meteoric material, so-called meteoric smoke particles (MSPs). Recently, we investigated the ice activation and growth behavior of MSP analogues under realistic mesopause conditions. Based on these measurements we presented a new activation model which largely reduced the uncertainties in describing ice particle formation. However, this activation model neglected the possibility that MSPs heat up in the low-density mesopause due to absorption of solar and terrestrial irradiation. Radiative heating of the particles may severely reduce their ice formation ability. In this study we expose MSP analogues (Fe2O3 and FexSi1−xO3) to realistic mesopause temperatures and water vapor concentrations and investigate particle warming under the influence of variable intensities of visible light (405, 488, and 660 nm). We show that Mie theory calculations using refractive indices of bulk material from the literature combined with an equilibrium temperature model presented in this work predict the particle warming very well. Additionally, we confirm that the absorption efficiency increases with the iron content of the MSP material. We apply our findings to mesopause conditions and conclude that the impact of solar and terrestrial radiation on ice particle formation is significantly lower than previously assumed.
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Chauhan, Vinita, Matthew Howland, and Ruth Wilkins. "A Comparitive Assessement of Cytokine Expression in Human-Derived Cell Lines Exposed to Alpha Particles and X-Rays." Scientific World Journal 2012 (2012): 1–9. http://dx.doi.org/10.1100/2012/609295.
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Alpha- (α-) particle radiation exposure has been linked to the development of lung cancer and has been identified as a radiation type likely to be employed in radiological dispersal devices. Currently, there exists a knowledge gap concerning cytokine modulations associated with exposure toα-particles. Bio-plex technology was employed to investigate changes in proinflammatory cytokines in two human-derived cell lines. Cells were irradiated at a dose of 1.5 Gy to eitherα-particles or X-rays at equivalent dose rates. The two cell lines exhibited a unique pattern of cytokine expression and the response varied with radiation type. Of the 27 cytokines assessed, only vascular endothelin growth factor (VEGF) was observed to be modulated in both cell lines solely afterα-particle exposure, and the expression of VEGF was shown to be dose responsive. These results suggest that certain proinflammatory cytokines may be involved in the biological effects related toα- particle exposure and the responses are cell type and radiation type specific.
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Wang, Li, Long Yang, Junjie Liu, and Pei Wang. "Study on Spectral Radiative Heat Transfer Characteristics of a Windowed Receiver with Particle Curtain." Energies 14, no. 10 (May 13, 2021): 2801. http://dx.doi.org/10.3390/en14102801.
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In this paper, a windowed receiver with a particle curtain is numerically simulated under full-spectrum conditions. The discrete phase model (DPM) is used to model the particle flow and interactions between the particle phase and the air phase. The scattering, absorption of the particle curtain and quartz glass window are considered in detail. The spectral characteristics of glass have an important influence on the heat transfer characteristics and the receiver efficiency. The results show that the quartz window can reduce the convective heat loss and the cavity re-radiation heat loss. Under the same conditions, the receiver efficiency of a windowed receiver with a particle curtain is increased by 11.9% compared with an aerowindow receiver with a particle curtain. Under the same mass flow, the particle curtain thickness and particle size have a non-negligible influence on the flow pattern and temperature distribution of the particle curtain. When the particle curtain thickness is low, the flow stability of the particle curtain is high; as the particle curtain thickness increases, the volume fraction of the particle curtain decreases, and the flow stability of the particle curtain decreases, which affects the shape of the curtain. The scattering and absorption characteristics of the particles are different, resulting in different net fluxes of incident radiation under the reflection of the particle curtain and the back wall. As the particle curtain thickness increases, the particle average exit temperature and the receiver efficiency show a trend of first increasing and then decreasing. When d = 30 mm, the incident radiation (G) at the position of the particle curtain is larger, the particle average exit temperature reaches 1156.72 K, and the receiver efficiency reaches 74.4%. Therefore, different particle sizes also have a significant impact on the flow pattern of the particle curtain and the radiation distribution inside it. In the range of 250–750 μm particle size, the particles average exit temperature reaches above 1150 K, and the receiver efficiency is above 72.6%. As the particle size increases, the particle average exit temperature, and the receiver efficiency show a trend of first decreasing and then increasing. When the particle size is 500 mm, the particle average exit temperature reaches 1175.8 K, and the receiver efficiency reaches 79.4%.
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Bijarniya, Jay Prakash, Jahar Sarkar, Shivam Tiwari, and Pralay Maiti. "Experimentally optimized particle–polymer matrix structure for efficient daytime radiative cooling." Journal of Renewable and Sustainable Energy 14, no. 5 (September 2022): 055101. http://dx.doi.org/10.1063/5.0098335.
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The polymer–particle matrix structure has attracted great interest for daytime radiative cooling due to its various advantages; however, cost-effective fabrication process development and proper material selection are crucial tasks. Herein, we illustrate the selection of fabrication process and materials based on development, characterization, and experimental performance. The initial selection is based on solar radiation backscattering and isotropic thermal emission properties of polymers and particles. Among potential polymers (PMMA, PVDF, and PU), PMMA is experimentally found more suitable for radiative cooling because of negligible absorption in the solar radiation spectrum. Among the selected particles (CaCO3, BaSO4, ZnO, and SiO2), the experimental performance of BaSO4 in the polymer matrix is found to be excellent. Furthermore, the optimum particle volumetric concentration is found at 70%, with an optimum thickness of 500 μm for the substrate independent radiative cooler. Spray-coating is found to be a better option for fabrication as compared to drop casting. The performance evaluation was carried out at Varanasi, India for over two months to investigate the environmental parameters' effect on performance. For an optimized structure, the observed maximum temperature drop from the ambient is 6 °C (17 °C lower than bare roof surface) during noontime and 9 °C during the evening. At ambient temperature, the recorded cooling power is 35 W/m2 at noon (solar peak) and 78 W/m2 in the evening for the experimentally optimized structure.
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Arkar, Kyaw, Mikhail M. Vasiliev, Oleg F. Petrov, Evgenii A. Kononov, and Fedor M. Trukhachev. "Dynamics of Active Brownian Particles in Plasma." Molecules 26, no. 3 (January 21, 2021): 561. http://dx.doi.org/10.3390/molecules26030561.
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Experimental data on the active Brownian motion of single particles in the RF (radio-frequency) discharge plasma under the influence of thermophoretic force, induced by laser radiation, depending on the material and type of surface of the particle, are presented. Unlike passive Brownian particles, active Brownian particles, also known as micro-swimmers, move directionally. It was shown that different dust particles in gas discharge plasma can convert the energy of a surrounding medium (laser radiation) into the kinetic energy of motion. The movement of the active particle is a superposition of chaotic motion and self-propulsion.
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Jordan, V. I. "Parametric Optimization of the Particle Temperature Distribution of the Gas-Thermal Flux by the Means of Thermal Radiation Spectrum of Particles." Izvestiya of Altai State University, no. 1(111) (March 6, 2020): 11–17. http://dx.doi.org/10.14258/izvasu(2020)1-01.
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This paper discusses the application of a method for measuring the distributed temperature parameter of particles based on the solution of the inverse problem that uses the experimentally recorded integral thermal radiation spectrum of heterogeneous gas-thermal flux particles. The output signal that registers the thermal radiation spectrum of particles is measured by a linear multi-element photodetector. The measuring equation for the output signal is presented as a Fredholm equation of the first kind with a temperature density distribution function and the Plank function.
A brief derivation of the inverse operator is provided for the solution of the inverse problem of determination of particle temperature distribution. Integral spectrum functions of thermal radiation of particles are derived for two model functions of particle temperature distribution. Parameters of these two model functions are optimized using the least-squares method and the experimentally obtained integral thermal radiation spectrum.
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Kryvdyk, V. "Particle Acceleration and Radiation in Magnetospheres of Collapsing Stars." Symposium - International Astronomical Union 195 (2000): 403–6. http://dx.doi.org/10.1017/s0074180900163296.
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Particle dynamics and nonthermal emission therefrom in the magnetospheres of collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of charged particles (power-law, relativistic Maxwell, and Boltzmann distributions) are considered. The radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and an initial power-law particle energy distribution in the magnetosphere. The effects can be observed by means of modern instruments.
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Nasr, K., R. Viskanta, and S. Ramadhyani. "An Experimental Evaluation of the Effective Thermal Conductivities of Packed Beds at High Temperatures." Journal of Heat Transfer 116, no. 4 (November 1, 1994): 829–37. http://dx.doi.org/10.1115/1.2911455.
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Combined conduction and radiation heat transfer in packed beds of spherical particles was investigated. Three different packing materials (alumina, aluminum, and glass) of various particle diameters (2.5 to 13.5 mm) were tested. Internal bed temperature profiles and corresponding effective thermal conductivities were measured under steady-state conditions for a temperature range between 350 K and 1300 K. The effects of particle diameter and local bed temperature were examined. It was found that higher effective thermal conductivities were obtained with larger particles and higher thermal conductivity packing materials. The measured values for the effective thermal conductivity were compared against the predictions of two commonly used models, the Kunii–Smith and the Zehner–Bauer–Schlu¨nder models. Both models performed well at high temperatures but were found to overpredict the effective thermal conductivity at low temperatures. An attempt was made to quantify the relative contributions of conduction and radiation. Applying the diffusion approximation, the radiative conductivity was formulated, normalized, and compared with the findings of other investigators.
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Veklenko, Boris A. "Coherent Stimulated Radiation, Coherent Spontaneous Radiation and Coupled Photon Pairs in Non-Uniform Thermally Excited Gaseous Media: Calculation Procedure." Light & Engineering, no. 03-2022 (June 2022): 61–67. http://dx.doi.org/10.33383/2021-121.
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This work continues the author’s study of the processes of interaction between a quantum electromagnetic field and a spatially non-uniform gaseous medium [1, 5]. Previously unknown optical effects caused by consideration of high-order quantum correlators were discovered. This is caused by the problem of calculation of high-order photonic correlators starting from the fourth order, which appears when the interaction between the quantum electromagnetic field is described using the Feynman diagrams, According to T.A. Matsubara’s technique applied nowadays, these correlators are just neglected. The author’s articles [1, 5] describe the calculation method allowing us to avoid thiscomplication. The method is based on the following. High-order quantum correlators appear when multi-particle problems are studied. If the number of particles is small (hydrogen atom), the problem disappears. Therefore, if we replace a multi-particle problem with a single-particle problem (even if this particle is rather complex), the problem will be solved. Such solution (by using the Γ-operators technique) is described in the said author’s articles. While the standard secondary quantisation technique uses operators of creation and destruction of separate particles, the Γ-operators technique deals with operators of creation and destruction of photon conglomerates (systems). It turns out that high-order correlators just do not appear when the Γ-operators technique is used. This article demonstrates a specific example of application of the Γ-technique.
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Evans, G., W. Houf, R. Greif, and C. Crowe. "Gas-Particle Flow Within a High Temperature Solar Cavity Receiver Including Radiation Heat Transfer." Journal of Solar Energy Engineering 109, no. 2 (May 1, 1987): 134–42. http://dx.doi.org/10.1115/1.3268190.
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A study has been made of the flow of air and particles and the heat transfer inside a solar heated, open cavity containing a falling cloud of 100-1000 micron solid particles. Two-way momentum and thermal coupling between the particles and the air are included in the analysis along with the effects of radiative transport within the particle cloud, among the cavity surfaces, and between the cloud and the surfaces. The flow field is assumed to be two-dimensional with steady mean quantities. The PSI-Cell (particle source in cell) computer code is used to describe the gas-particle interaction. The method of discrete ordinates is used to obtain the radiative transfer within the cloud. The results include the velocity and temperature profiles of the particles and the air. In addition, the thermal performance of the solid particle solar receiver has been determined as a function of particle size, mass flow rate, and infrared scattering albedo. A forced flow, applied across the cavity aperture, has also been investigated as a means of decreasing convective heat loss from the cavity.
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Frankel, Ari, H. Pouransari, F. Coletti, and A. Mani. "Settling of heated particles in homogeneous turbulence." Journal of Fluid Mechanics 792 (March 8, 2016): 869–93. http://dx.doi.org/10.1017/jfm.2016.102.
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We study the case of inertial particles heated by thermal radiation while settling by gravity through a turbulent transparent gas. We consider dilute and optically thin regimes in which each particle receives the same heat flux. Numerical simulations of forced homogeneous turbulence are performed taking into account the two-way coupling of both momentum and temperature between the dispersed and continuous phases. Particles much smaller than the smallest flow scales are considered and the point-particle approximation is adopted. The particle Stokes number (based on the Kolmogorov time scale) is of order unity, while the nominal settling velocity is up to an order of magnitude larger than the Kolmogorov velocity, marking a critical difference with previous two-way coupled simulations. It is found that non-heated particles enhance turbulence when their settling velocity is sufficiently high compared to the Kolmogorov velocity. Energy spectra show that the non-heated particle settling impacts both the very small and very large flow scales, while the intermediate scales are weakly affected. When heated, particles shed plumes of buoyant gas, further modifying the turbulence structure. At the considered radiation intensities, clustering is strong but the classic mechanism of preferential concentration is modified, while preferential sweeping is eliminated or even reversed. Particle heating also causes a significant reduction of the mean settling velocity, which is caused by rising buoyant plumes in the vicinity of particle clusters. The turbulent kinetic energy is affected non-monotonically as the radiation intensity is increased due to the competing effects of the downward gravitational force and the upward buoyancy force. The thermal radiation influences all scales of the turbulence. The effects of settling and buoyancy on the turbulence anisotropy are also discussed.
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Zhang, Xiaolin, Yu Zhou, Yuanzhi Wang, Aojie Huang, Chang Gao, Siqi He, and Mao Mao. "Scavenging of Black Carbon Aerosols by Radiation Fog in Urban Central China." Atmosphere 13, no. 2 (January 27, 2022): 205. http://dx.doi.org/10.3390/atmos13020205.
Full textAbstract:
Radiation fog episodes are characterized by aerosol radiative properties measured at Hefei in urban central China, which hopefully benefits numerical weather prediction and air quality improvement for local governments. In this study, a high mean aerosol optical depth (AOD) is seen over Hefei during the sampling period, whereas an AOD of ~3.0 at 550 nm is observed during the fog episodes. We redefine the fog scavenging coefficient based on its starting and ending points in time, and a black carbon (BC) scavenging coefficient of 30% is observed. Meanwhile, the fog process cannot reduce aerosol number concentrations at size bins between 0.5 and 0.6 μm, whereas a mean particle scavenging coefficient of 21% at sizes within 0.6–1 μm is seen. Significantly large median aerosol scattering coefficient (2690 Mm−1) and absorption coefficient (446 Mm−1) at 550 nm, and low scattering Angstrom exponent in fog are observed, while distinctive particle size distributions between fog and haze are shown. Particle mean size distribution in fog is lower than that in haze at size bins between 0.7 and 2.1 μm, whereas the reverse is true for sizes within 0.5–0.7 μm and larger than 2.1 μm. Aerosol scattering during fog episodes undergoes a bigger increase than particle absorption, and this increase of scattering in fog is even higher than in haze. Median single scattering albedos of 0.86, 0.82, and 0.76 at 550 nm and aerosol radiative forcing efficiencies of −15.0, −14.0, and −10.0 W/m2 are seen for fog, haze and clear periods, respectively, and more negative radiative forcing efficiency emphasizes the significance of fog episodes on climate forcing. Our study clearly reveals the changes of aerosol radiative properties during radiation fog, particularly a synchronous variation of fog aerosol backscattering ratio with the visibility, indicating that more large particles are formed with fog becoming thicker and are scavenged with the dissipation of fog.
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Serret, Olivier. "Gravitational waves or particle radiation?" Physics Essays 30, no. 3 (September 15, 2017): 298–99. http://dx.doi.org/10.4006/0836-1398-30.3.298.
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