Radiation Mechanism Research Articles

Probing the low-energy particle content of blazar jets through MeV observations

Many of the blazars observed by Fermi actually have the peak of their time-averaged gamma-ray emission outside the ∼GeV Fermi energy range, at ∼MeV energies. The detailed shape of the emission spectrum around the ∼MeV peak places important constraints on acceleration and radiation mechanisms in the blazar jet and may not be the simple broken power law obtained by extrapolating from the observed X-ray and GeV gamma-ray spectra. In particular, state-of-the-art simulations of particle acceleration by shocks show that a significant fraction (possibly up to ≈90%) of the available energy may go into bulk quasi-thermal heating of the plasma crossing the shock rather than producing a nonthermal power-law tail. Other gentler but possibly more pervasive acceleration mechanisms, such as shear acceleration at the jet boundary, may result in a further build-up of the low-energy (γ ≲ 102) particle population in the jet. As already discussed for the case of gamma-ray bursts, the presence of a low-energy Maxwellian-like bump in the jet particle energy distribution can strongly affect the spectrum of the emitted radiation, for example producing an excess over the emission expected from a power-law extrapolation of a blazar’s GeV-TeV spectrum. We explore the potential detectability of the spectral component ascribable to a hot quasi-thermal population of electrons in the high-energy emission of flat-spectrum radio quasars (FSRQs). We show that for the typical physical parameters of FSRQs, the expected spectral signature is located at ∼MeV energies. For the brightest Fermi FSRQ sources, the presence of such a component will be constrained by the upcoming MeV Compton Spectrometer and Imager (COSI) satellite.

High energy radiation induced degradation of poly(lactic acid) (PLLA) film: radiation chemical yield, kinetics, mechanism and radioracemization evidences

High energy radiation induced degradation of poly(lactic acid) (PLLA) film: radiation chemical yield, kinetics, mechanism and radioracemization evidences

Radiation Mechanism of Interaction with Matter

Radiation Mechanism of Interaction with Matter

Disinfection effectiveness and mechanism of in-duct microwave radiation on A. versicolor adhere to a SiC composite filter

In this research, the disinfection effectiveness and mechanism of in-duct microwave radiation on A. versicolor aerosols adhere to the SiC composite filter are experimentally studied. Firstly, the disinfection effectiveness of in-duct microwave radiation on A. versicolor adhere to the SiC composite filter and its influencing factors are studied. Subsequently, the disinfection mechanism, i.e. the non-thermal and thermal effects, are analysed. Results show that A. versicolor adhere to the SiC composite filter can be efficiently disinfected by in-duct microwave radiation under appropriate operating conditions. Specially, the disinfection rate of various measurement points on the SiC composite filter can reach more than 90% when the operating power is 700 W and disinfection time is 5 min, and about 100% when the disinfection time extended 15 min. The disinfection rate increases with the increments of the operating power and disinfection time, but compared to latter, the increment of the former has a greater impact on the disinfection rate. In the process of microwave disinfection of A. versicolors, non-thermal effect is present but their impact is relatively limited. Ideal disinfection effectiveness cannot be achieved by non-thermal effect alone. Effective disinfection of A. versicolor requires the combination of non-thermal and thermal effects.

Black Hole Mass and Optical Radiation Mechanism of the Tidal Disruption Event AT 2023clx

We present the optical light curves of the tidal disruption event AT 2023clx in the declining phase, observed with Mephisto. Combining our light curve with the ASAS-SN and ATLAS data in the rising phase, and fitting the composite multi-band light curves with MOSFiT, we estimate black hole mass for AT 2023clx is between 105.67 and 105.82 M ⊙. This event may be caused by either a full disruption of a 0.1 M ⊙ star, or a partial disruption of a 0.99 M ⊙ star, depending on the data adopted for the rising phase. Based on those fit results and the non-detection of soft X-ray photons in the first 90 days, we propose that the observed optical radiation is powered by stream-stream collision. We speculate that the soft X-ray photons may gradually emerge in 100–600 days after the optical peak, when the debris is fully circularized into a compact accretion disk.

Thermal management of radiation mechanism over a stretchable curved surface inside the circle: performance enhancement of molybdenum disulfide and silicon dioxide hybrid nanofluid for thermal technology advancement

The main perspective of this research focuses on addressing the pressing industry problem related to energy inefficiency by studying the heat transfer improvement of solar radiative and heat absorption/emission phenomena over a stretchable curved sheet inside the circle. To increase the model novelty, the combined influence of thermal relaxation, Newtonian heating, radiation mechanism, and Darcy-Forchheimer are included in the problem formulation of governing equations. Furthermore, this research employs the Cattaneo–Christov heat theory model to investigate the thermal flux via utilising the above-mentioned phenomenon with the purpose of advancing thermal technology. In this perspective, Molybdenum disulfide ( Mo S 2 ) with a base fluid of Propylene glycol ( C 3 H 8 O 2 ) is utilised as nanoparticles for nanofluid (NFs), and for making hybrid nanofluid (HNFs), Molybdenum disulfide ( Mo S 2 ) and silicon dioxide ( Si O 2 ) are utilised with of Propylene glycol ( C 3 H 8 O 2 ) . The equations are converted into ordinary Differential equations using Similarity variables. Shifted Legendre collocation scheme (SLCS) is then utilised to solve the simulation of the modelled equations. The findings show that the solar radiation effects boosted the heating performance of the Mo S 2 − Si O 2 / C 3 H 8 O 2 hybrid nanofluid.

Research and Prospects of Radiation Mechanisms in Macroscopic Astrophysics

In the field of astrophysics, the study of radiation from different celestial bodies is of great significance. Celestial bodies such as stars, galaxies, and planets emit various types of radiation. However, traditional research has limitations in understanding the radiation mechanisms of some celestial bodies, and the specific processes and factors affecting radiation are not fully clear, which restricts the further development of astrophysics. In this study, a multi-band observation and comprehensive data analysis method is adopted. Through the calibration and normalization of observation data, spectral analysis, image analysis, and other means, the characteristics and mechanisms of celestial body radiation are explored. The results show that different celestial bodies have unique radiation characteristics and evolution processes. This research can optimize the design and planning of space missions. Galaxies consist of numerous stars and have unique radiation features due to active galactic nuclei and interstellar medium. Planets reflect and emit radiation based on their interaction with stars and internal heat sources. This research holds significant value in understanding the structure and evolution of the universe. It provides insights into the physical processes occurring in celestial bodies and helps people better understand the nature of the cosmos.

New Insights on Gamma-Ray Burst Radiation Mechanisms from Multiwavelength Observations

Abstract The study of high-energy gamma-ray emission from gamma-ray bursts (GRBs) involves complex synchrotron radiation and synchrotron self-Compton scattering (SSC) mechanisms with multiple parameters exhibiting a wide distribution. Recent advancements in GRB research, particularly the observation of very high energy (VHE, $\rm >100~GeV$) radiation, have ushered in a new era of multiwavelength exploration, offering fresh perspectives and limitations for understanding GRB radiation mechanisms. This study aimed to leverage VHE observations to refine constraints on synchrotron + SSC radiation from electrons accelerated by forward shocks. By analyzing two external environments - the uniform interstellar medium and stratified stellar wind medium, we conducted spectral and variability fitting for five specific bursts (GRB~180720B, GRB~190114C, GRB~190829A, GRB~201216C, and GRB~221009A) to identify the optimal parameters characterizing these events. A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factor $\epsilon_B$ is more concentrated with VHE emissions. This suggests that VHE emissions may offer greater constraints on this microphysical parameter. Additionally, we found that the energy budget between VHE and keV-MeV $\gamma$-ray emissions under the SSC radiation exhibits an almost linear relationship, which may serve as a tool to differentiate radiation mechanisms. We anticipate future statistical analyses of additional VHE bursts to validate our findings.

Unraveling Temperature Distribution Within Crystalline Silicon PV Modules by Different Finite Element Method‐Based Thermal Modeling Approaches

AbstractIn this work, the steady‐state spatial temperature distribution in commercial high‐efficiency crystalline silicon PV modules is studied using different FEM‐based thermal models that encompass conductive, convective, and radiative heat transfer mechanisms. The results show that the lateral temperature distribution within the PV module depends on the module inclination angle and may be highly inhomogeneous, with a temperature difference of ≈5 °C between its warmest and coolest solar cells. Furthermore, It is demonstrated that wind plays a crucial role in determining the operating temperature of PV devices. Specifically, it is shown that forced convection has an even more significant positive effect at higher wind speeds and larger PV module dimensions since the transformation of laminar to turbulent wind contributes to additional cooling. Finally, the power losses associated with the lateral temperature variations across the PV module are analyzed. The results show that the effect of temperature inhomogeneity plays a negligible role in the performance of standard single‐junction silicon PV modules due to a very small temperature coefficient of the solar cell short‐circuit current.

Numerical analysis of the energy efficiency measures for improving the truck cabin thermal performance

This paper presents the numerical analysis of the thermal performance of a truck cabin. The results obtained for a standard truck cabin setup are compared to the configurations with energy saving measures implemented. As a very promising energy efficiency measure, the application of the infrared panels is considered. Based on the radiative heat transfer mechanism, the infrared panels influence directly all inner cabin surfaces. This includes also the truck cabin occupants, whose perception of the indoor comfort reaches neutral values much faster and at lower ambient air temperatures. As a result, there is much lower energy demand for the cabin heating, required for maintaining the desired indoor comfort. The preliminary numerical analysis indicates the energy saving potential of around 30% for this innovative cabin thermal concept, as compared to the original energy demand for the traditional cabin heating configuration.

Conformal leaky wave antenna based on gap waveguide technology

Abstract Due to structural and aerodynamic limitations, conformal antennas are increasingly sought after in antenna design. Gap waveguide technology has also gained traction for its potential in leaky wave antenna development. This paper proposes a novel conformal leaky wave antenna utilizing this emerging gap waveguide technology. Prior research has not extensively explored the radiation characteristics of such antennas on curved and conformal surfaces. This work addresses this gap by investigating the design procedure, radiation mechanism, and optimization methods for leaky wave antennas on conformal surfaces. The proposed antenna achieves a gain of approximately 18 dB and a scanning angle ranging from 1 to 33 degrees within the frequency band of 9.5 GHz to 12 GHz. Fabrication and subsequent measurements of the antenna were conducted, with the results demonstrating good agreement with the simulations.

Interplay between classical and quantum dissipation in light-matter dynamics.

A quantum-electrodynamics approach is presented to describe the dynamics of electrons that exchange energy with both photon and phonon baths. Our ansatz is a dissipative quantum Liouville equation, cast in the Redfield form, with two driving terms associated with radiative and vibrational relaxation mechanisms, respectively. Remarkably, within the radiative contribution, there is a term that exactly replicates the expression derived from a semiclassical treatment where the power dissipated by the electronic density is treated as the emission from a classical dipole [Bustamante et al., Phys. Rev. Lett. 126, 087401 (2021)]. Analysis of the distinct contributions to the total radiation shows that the semiclassical emission depends on the coherences, with the remainder of the quantum-electrodynamics driving term determined by the excited populations, thus accounting for the relaxation of eigenstates or incoherent mixed states. This approach is used to investigate the response of the Su-Schrieffer-Heeger model for trans-polyacetylene to both pulsed and continuous laser irradiation. Upon excitation with a short pulse and in the absence of the vibrational mechanism, the conducting band population exhibits a stepwise relaxation, characterized by cycles of exponential decay followed by a transient subradiant state. The latter arises from the collective coupling between Bloch states featuring a quasi-continuum energy spectrum in reciprocal space. The separate examination of the semiclassical dynamics reveals that it is this contribution that is responsible for the collective behavior. If vibrational dissipation is active, following the laser pulse, the excited electrons rapidly populate the minimum of the conduction band, and the emission spectrum shifts to lower frequencies with respect to absorption. Meanwhile, continuous irradiation drives the system to a stationary state with a broad emission spectrum.

Main Heat Transfer Mechanisms in Hot Stamping Processes: a Review

Objectives: The article reviews heat transfer mechanisms in the hot stamping process, highlighting models to calculate the interfacial heat transfer coefficient (IHTC), crucial for optimizing the cooling and quality of formed products. Theoretical Framework: In hot stamping of high-strength steels, the IHTC is affected by variables such as contact pressure, roughness and temperature. Cooling efficiency directly impacts the temperature distribution and martensitic microstructure of the material, essential for structural strength. Method: The review compares IHTC calculation methods, such as inverse heat conduction analysis and Newton's law of cooling, detailing the convection, radiation and conduction mechanisms at each stage of the process: transfer, positioning and forming. Results and Discussion: The inverse heat conduction analysis proved to be the most accurate for determining the IHTC, compared to the finite element method (FEM). The study suggests that efficient cooling channels and high conductivity materials in the matrix reduce cooling time and improve the quality of the final product. Research Implications: Findings provide a basis for improving thermal management in hot stamping, reducing cycle time and increasing productivity. Originality/Value: This work contributes a comprehensive reference on IHTC, assisting researchers and engineers in optimizing heat transfer and production efficiency in the manufacture of automotive components.

Wideband star-shaped antenna based on artificial magnetic conductor surface for unidirectional radiation

Gathering the advantages of low profile, high gain, high efficiency, and wideband operation in a planar antenna is a challenging objective for the antenna designer. Low profile wideband antennas are usually characterized by low gain. An antenna of wideband impedance matching usually suffers continuous variations of the gain over such a wideband due to the variation of the radiation mechanisms and surface current distributions over the frequency band of impedance matching. Therefore, the motivation of the present work is to provide both impedance matching and stabilized high gain by the aid of wideband artificial magnetic conductor (AMC) with a design of the unit cell that is suitable to the antenna structure and the desired frequency band. The present work, proposes the utilization of low-size wideband AMS surface (AMCS) to be placed behind a wideband omnidirectional antenna to enhance the gain over the frequency band of operation. In this way, the radiating structure combines high gain and wideband operation in the same design. A wideband planar monopole printed antenna is designed to operate as omnidirectional antenna with perfect impedance matching and radiation efficiency over the frequency band 3.6-7.2GHz when placed in free space. The gain of the free-standing antenna varies from 2dBi to 4.5dBi over the frequency band. A wideband AMCS is designed to enhance the antenna gain over frequency band of operation. The designed AMCS is composed of only 3×3 unit cells and overall dimensions of 10×10cm. This surface is placed parallel to the planar antenna at a distance 1.7cm behind it. The enhanced gain of the radiating structure of the AMCS-backed antenna reaches 8.5dBi without affecting the bandwidth over which the input impedance is matched to the feeding line. The radiation efficiency of the AMCS-backed antenna is maintained above 98% over the frequency band of operation (3.7-7.2GHz). The wideband antenna and the AMCS are fabricated for practical evaluation of the overall AMCS-backed antenna performance including the measurements of impedance matching, gain and radiation efficiency. The measurements and simulation results are in good consent.

Mechanism and performance of thermal radiation recycling for in-space 3D printed continuous carbon fibre-reinforced PEEK composites

ABSTRACT The benefits of space recycling lie in reducing launch mass and achieving self-sufficiency. For 3D printed continuous fibre-reinforced composites (CFRCs), a reverse melt recycling technology was proposed, involving heating resin opposite to the 3D printing path and continuously peeling-off the fibres from the melt. An infrared radiation heating recycling device suitable for a vacuum environment was designed and the temperature distributions were optimised, achieving recycling of continuous carbon fibre-reinforced polyether ether ketone (CF/PEEK) thin-walled rotational structures. The recycled filaments with diameters of 0.7 and 0.8 mm could achieve good surface quality and low pore defects. The porosity decreased from 11.2% of original samples to 5.7% of remanufactured samples, leading to improvements in mechanical properties with flexural strength and modulus increased by 4.8% and 50.8% respectively. Overall, the recycling technology emphasised a non-degradation recycling solution for 3D-printed CFRCs in space to form a full lifecycle application model for space composites.

The proposed mechanism of glow of mesosphere clouds

The question of the physical mechanism of electromagnetic radiation scattering by mesospheric (noctilucent) clouds is considered. A hypothesis has been expressed about the special electromagnetic characteristics of nanometer-sized ice particles that make up mesospheric clouds. Particle ice consists of a recently discovered crystalline modification of water — ice 0, formed by the condensation of vapor on dust particles at temperatures of –140…–23°C. Ice 0 is a ferroelectric, and upon contact with a dielectric, a layer with high electrical conductivity is formed. Due to plasmon resonance in nanosized layers, strong scattering of electromagnetic radiation occurs over a wide frequency range. This mechanism causes the glow of noctilucent clouds when illuminated by the radiation of the Sun.

Assessing Radiative Feedbacks and Their Contribution to the Arctic Amplification Measured by Various Metrics

AbstractArctic amplification (AA), characterized by a more rapid surface air temperature (SAT) warming in the Arctic than the global average, is a major feature of global climate warming. Various metrics have been used to quantify AA based on SAT anomalies, trends, or variability, and they can yield quite different conclusions regarding the magnitude and temporal patterns of AA. This study examines and compares various AA metrics for their temporal consistency in the region north of 70°N from the early twentieth to the early 21st century using observational data and reanalysis products. We also quantify contributions of different radiative feedback mechanisms to AA based on short‐term climate variability in reanalysis and model data using the Kernel‐Gregory approach. Albedo and lapse rate feedbacks are positive and comparable, with albedo feedback being the leading contributor for all AA metrics. The net cloud feedback, which has large uncertainties, depends strongly on the data sets and AA metrics used. By quantifying the influence of internal variability on AA and related feedbacks based on global climate model ensemble simulations, we find that water vapor and cloud feedbacks are most heavily affected by internal variability.

Impact of the Abrasive Solution Heating Process With Different Techniques on the Etching Parameters for the SSNTD (CN-85)

Abstract The presented work aims to compare and analyze the impact of the abrasive solution heating process using three different techniques on the etching parameters for the solid-state nuclear track detector (SSNTD) (CN-85). Water bath technique (WB) is using water as a conduction medium of heat transfer to heat the etching solution. The thermal oven technique (TO) is using air as a convection heat transfer medium to heat the etching solution. Finally, the micro-wave technique (MW) as electromagnetic radiation no need for a medium to heat the etching solution. That comparison will be achieved at different irradiation times to an Americium-241 source (241Am) of 5.486 MeV energy and 10 μCi activity as an alpha particle's emitter. Two irradiation times 10 s and 20 s are applied. Small pieces of CN-85 detectors (1 × 1) cm2 were used. CN-85 detector parameters of the etching process, with the three applying techniques (WB, TO, and MW), are estimated and compared. The obtained results from the three techniques are compared. The etching process time is developed to nearly 5 min for MW with heating by radiation mechanism compared to 25–35 min for etching techniques (WB and TO) with heating by conduction and convection mechanisms, respectively. The efficiency of MW technique with range of from 70% to 75% are five times greater than that for WB and TO techniques.

Electromagnetic radiation of granite under dynamic compression

To elucidate the characteristics and mechanism of electromagnetic radiation in granite under impact loading, based on the quasi-static compression tests, this paper conducts dynamic compression experiments on granite using Hopkinson pressure bar and one-stage light-gas gun as loading methods. Combined with experimental and theoretical analyses, the relationship between mechanical and electromagnetic responses under impact loads of different intensities, and the time-domain signals of electromagnetic radiation generated by a single crack under different strain rates are studied. The intensity and frequency of electromagnetic radiation increase with the increasing compressive strain rate. According to the thermal activation theory, it reveals the microscopic mechanism of the transition from intergranular microcracks to transgranular microcracks in terms of strain sensitivity. It also serves as the physical basis for the increase in electromagnetic radiation intensity amplitude and frequency with increasing compressive strain rate. Transgranular microcracks are the primary cause of electromagnetic radiation generated by fractures.

Phenomenology of an extended 1+2 Higgs doublet model with S3 family symmetry

In order to explain the mass hierarchy and mixing pattern in the leptonic sector, we explore an extension of the Standard Model whose scalar sector includes one active and two inert doublets as well as some scalar singlets. The model includes a S3 family symmetry supplemented by extra cyclic symmetries. As a consequence of our construction, a Dark Matter (DM) candidate is predicted and its properties are consistent with the observed cosmic abundances and the constraints imposed by direct and indirect detection experiments. The model allows Charged Lepton Flavor Violation (CLFV) processes like μ→eγ and μ→3e, but the predicted branching ratios align with experimental limits. Additionally, our analysis elucidates the generation of the active neutrino masses through a one-loop radiative seesaw mechanism matching the observed neutrino oscillation data. The model agrees with experimental data on Higgs Diphoton decay rates and on oblique parameters.