Siga este link para ver outros tipos de publicações sobre o tema: Radiation.
Artigos de revistas sobre o tema "Radiation"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores artigos de revistas para estudos sobre o assunto "Radiation".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja os artigos de revistas das mais diversas áreas científicas e compile uma bibliografia correta.
1
Renwick, Bryce, Nimra Zaidi, Marta Madurska, Khalid Irshad, Donald Bain e Donald Reid. "RADIATION PROTECTION IN COMPLEX ENDOVASCULAR PROCEDURES". International Journal of Surgery and Medicine 3, n.º 1 (2017): 1. http://dx.doi.org/10.5455/ijsm.endovascular-radiation.
Texto completo da fonte
2
Kolesnichenko, Aleksandr Vladimirovich. "Simple waves and small perturbations in radiative gas dynamics". Keldysh Institute Preprints, n.º 48 (2023): 1–34. http://dx.doi.org/10.20948/prepr-2023-48.
Texto completo da fonteResumo:
The paper analyses one-dimensional simple waves and small-amplitude disturbances in radiating and scattering grey gas. The governing equation of radiation acoustics describing the dynamics of simple waves is derived. Radiation-thermal dissipation conditions and radiation resistance force are introduced into this equation to describe the propagation and attenuation of various radiation perturbation waves. To study non-equilibrium wave phenomena in a radiating medium, the phenomenological Whitham method is used. This method is an effective way to analyse fundamental modes when more than one velocity appears in the governing equation. The use of this method is demonstrated in the paper by considering the evolution of one-dimensional harmonic waves caused by a short-wave initial perturbation of the equilibrium state of the radiating and scattering medium. For all wave modes, analytical solutions have been obtained, which allow us to understand their physical significance. These solutions can be, in particular, an additional test for radiative hydrodynamic codes operating in the radiative acoustics regime. The general approach can be useful in the development of higher-order Godunov numerical schemes for radiation hydrodynamics problems.
3
Kolesnichenko, Aleksandr Vladimirovich. "To simple waves and small-amplitude perturbations in radiation gasodynamics". Mathematica Montisnigri 59 (2024): 28–48. http://dx.doi.org/10.20948/mathmontis-2024-59-4.
Texto completo da fonteResumo:
The paper analyzes one-dimensional simple waves and small-amplitude perturbations in radiating and scattering gray gas. The governing equation of radiation acoustics describing the dynamics of simple waves is derived. The conditions of radiation-thermal dissipation and radiation resistance force are introduced into this equation to describe the propagation with dissipation and attenuation of various radiation perturbation waves. The phenomenological approximate Whitham method is used to investigate non-equilibrium wave phenomena in radiative medium. This method is an effective way to analyze fundamental modes when more than one velocity appears in the governing equation. The use of this method is demonstrated in this paper by considering the evolution of one-dimensional harmonic waves caused by a short-wave initial perturbation of the equilibrium state of the radiating and scattering medium. Analytical solutions are obtained for all wave modes, which allow us to interpret their physical meaning. These solutions can be, in particular, an additional test for radiative hydrodynamic codes operating in the radiative acoustics regime. The presented approach may be useful in detailing higher-order numerical Godunov schemes for radiation acoustics problems.
4
Salim, Shesnia. "“Academic success depends upon research and publications!” - PHILIP ZIMBARDO". Journal of Radiation Research and Imaging 2, n.º 1 (9 de maio de 2023): 9–10. http://dx.doi.org/10.46439/radiation.2.007.
Texto completo da fonte
5
Schwarz, Benjamin, Matthias Sammer, Nicole Matejka, Sarah Rudigkeit e Judith Reindl. "High-LET targeted microbeam irradiation induces local chromatin reorganization in living cells showing active basal mechanisms at highly complex DNA damage sites". Journal of Radiation Research and Imaging 2, n.º 1 (9 de maio de 2023): 1–8. http://dx.doi.org/10.46439/radiation.2.006.
Texto completo da fonteResumo:
DNA repair eukaryotic cells have additional protective mechanisms that avoid uncontrolled interaction of different parts of the chromatin and damaged regions. Key factors here are the regulation of chromatin density and mobility. The 4D (temporal and spatial) organization of chromatin is controlling this security barrier by regulating the accessibility of genes, flexibility of DNA, and its ability to move inside the nucleus. How this regulation mechanisms are involved in DNA repair upon radiation damage is until now rarely known but an important part to understand the enhanced effectiveness of high linear energy transfer (LET) particles. The damage recognition via PARP1 and the subsequent chromatin decondensation via PARylation is a crucial step in the DNA damage response (DDR). Upon We used the SNAKE microbeam with a beam spot size of <1 µm to induce highly localized DNA damage in living cells using 55 MeV Carbon ions to investigate the chromatin rearrangements in the early stage of DDR. The nuclei were irradiated with a cross pattern consisting of 1000 ions per spot and 25 spots per cell either with one (11 000 Gy), two (22 000 Gy), or three crosses (33 000 Gy). The chromatin rearrangement was imaged live for several minutes after irradiation at the beam using SiR chromatin stain. Upon 91% of the cells show a localized decondensation starting from a few seconds up to minutes after irradiation. The chromatin is decondensed by 6%-8% in the beam path with a local condensation at the edges of up to 8%. Our results suggest that chromatin decondensation is a fast process in the first few seconds after damage induction. Furthermore, decondensation status does not change over minutes, which gives evidence that this process and therefore DDR is paused or even stopped. In combination with the existing knowledge about early reactions to damage induction our data support the model of PARP induced chromatin decondensation. Furthermore, it is evident that also ultra-high doses of radiation are, in first place not able to inactivate initial basal mechanisms as response to damage induction.
6
Kitov, B. I. "Fluorescence of anisotropic primary X-ray radiation". Аналитика и контроль 26, n.º 1 (2022): 6–12. http://dx.doi.org/10.15826/analitika.2022.26.1.002.
Texto completo da fonteResumo:
In the X-ray spectral fluorescence analysis, the anisotropy of primary radiation results in an uneven radiation of a sample’s surface, strengthening the role of some sections and weakening the role of others. The goal of the current work was to determine the minimal distance from the window of the X-ray tube with a cone-shaped anode at which the intensity of the sample’s radiation becomes homogeneous. The research method was the computer modeling of the X-ray fluorescence experiment. The working model was built on the basis of two equations for the densities of the fluxes of braking and characteristic radiations of the massive anode, which took into account the absorption of primary radiation by the anode’s material and the back-scattering of electrons. The ring source was represented in the model as the sum of infinitely small linear elements of equal power, and the sample was disc-shaped and coaxial with the source. The calculation diagram was very well consistent with the experimental diagram of radiation’s direction described in the research literature. Two spatial distributions were calculated. The first one described the distribution of primary radiation’s intensity on the surface of the sample, while the second one described the distribution of the fluorescent radiation, which was more valuable for the X-ray spectrometry. The calculations showed that although the second distribution, unlike the first one, considered the absorption of the primary radiation and secondary radiation in the sample, the shapes of both radiations were close. It was demonstrated that the area of the sample, which carried the most information on the composition of the irradiated material, was ring-shaped, and the width of this ring depended on the distance to the X-ray tube’s window. As the distance increased, the diagram of the spatial distribution of the radiation’s intensity became smoother, and, when the distance exceeded two diameters of the anode, the radiation became homogeneous. The constructed model, which considered the anisotropy of the primary analysis, could be applied in the method of fundamental parameters of X-ray fluorescence analysis for a spectrometer with compressed geometry.
7
Gore, J. P., U. S. Ip e Y. R. Sivathanu. "Coupled Structure and Radiation Analysis of Acetylene/Air Flames". Journal of Heat Transfer 114, n.º 2 (1 de maio de 1992): 487–93. http://dx.doi.org/10.1115/1.2911299.
Texto completo da fonteResumo:
A coupled radiation-structure analysis of turbulent, non-premixed, strongly radiating acetylene/air flames is described. The analysis extends the laminar flamelet concept to include the effects of local radiative heat loss/gain. A new method for the calculation of the radiative source term is presented. New measurements of mean and fluctuating emission temperatures and radiation intensities, and previous data concerning flame structure are used to evaluate the predictions. Results show good agreement between measurements and predictions of flame structure similar to past uncoupled calculations. The mean emission temperatures and the mean visible radiation intensities are substantially underpredicted by the uncoupled analysis. The coupled calculations provide reasonable estimates of both quantities.
8
Guseva, A. A., e I. S. Grigor’Ev. "Mathematical simulation of aircraft engine jet exhausts radiation". Journal of «Almaz – Antey» Air and Space Defence Corporation, n.º 4 (30 de dezembro de 2018): 30–36. http://dx.doi.org/10.38013/2542-0542-2018-4-30-36.
Texto completo da fonteResumo:
The paper deals with the problems of mathematical simulation of aircraft engine jet exhausts radiation, the simulation being carried out by means of shader subroutines for the concurrent computation of the radiative transfer equation on the video card resources. The combination of an analytical model of an isobaric jet and ray tracing of computation of the radiative transfer equation allows us to develop a flexible model of aircraft jet radiation, the model taking into account the main parameters of streams in the jet and in the co-current flow, the spectral lines of the radiating components, and provides real-time computation. For the graphic implementation of the model, the OpenGL standard is used
9
Degl'Innocenti, Egidio Landi. "The Physics of Polarization". Proceedings of the International Astronomical Union 10, S305 (dezembro de 2014): 1. http://dx.doi.org/10.1017/s1743921315004433.
Texto completo da fonteResumo:
AbstractThe introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.The introductory lecture delivered at the Symposium has covered the subjects itemized above with the exclusion of Sections 10, 11, 14, 18, and 19.
10
Tan, Yuantao, Yaoke Duan, Qing Chi, Rong Wang, Yue Yin, Dongjie Cui, Shuang Li et al. "The Role of Reactive Oxygen Species in Plant Response to Radiation". International Journal of Molecular Sciences 24, n.º 4 (8 de fevereiro de 2023): 3346. http://dx.doi.org/10.3390/ijms24043346.
Texto completo da fonteResumo:
Radiation is widespread in nature, including ultraviolet radiation from the sun, cosmic radiation and radiation emitted by natural radionuclides. Over the years, the increasing industrialization of human beings has brought about more radiation, such as enhanced UV-B radiation due to ground ozone decay, and the emission and contamination of nuclear waste due to the increasing nuclear power plants and radioactive material industry. With additional radiation reaching plants, both negative effects including damage to cell membranes, reduction of photosynthetic rate and premature aging and benefits such as growth promotion and stress resistance enhancement have been observed. ROS (Reactive oxygen species) are reactive oxidants in plant cells, including hydrogen peroxide (H2O2), superoxide anions (O2•−) and hydroxide anion radicals (·OH), which may stimulate the antioxidant system of plants and act as signaling molecules to regulate downstream reactions. A number of studies have observed the change of ROS in plant cells under radiation, and new technology such as RNA-seq has molecularly revealed the regulation of radiative biological effects by ROS. This review summarized recent progress on the role of ROS in plant response to radiations including UV, ion beam and plasma, and may help to reveal the mechanisms of plant responses to radiation.
11
Philipona, Rolf, Andreas Kräuchi, Rigel Kivi, Thomas Peter, Martin Wild, Ruud Dirksen, Masatomo Fujiwara, Miho Sekiguchi, Dale F. Hurst e Ralf Becker. "Balloon-borne radiation measurements demonstrate radiative forcing by water vapor and clouds". Meteorologische Zeitschrift 29, n.º 6 (25 de novembro de 2020): 501–9. http://dx.doi.org/10.1127/metz/2020/1044.
Texto completo da fonte
12
Smith, Warren P., Melville E. Nicholls e Roger A. Pielke. "The Role of Radiation in Accelerating Tropical Cyclogenesis in Idealized Simulations". Journal of the Atmospheric Sciences 77, n.º 4 (20 de março de 2020): 1261–77. http://dx.doi.org/10.1175/jas-d-19-0044.1.
Texto completo da fonteResumo:
Abstract Recent numerical modeling studies indicate the importance of radiation in the transformation from a tropical disturbance to a tropical depression, a process known as tropical cyclogenesis. This paper employs a numerical modeling framework to examine the sensitivity to radiation in idealized simulations for different initial vortex strengths, and in doing so highlights when during tropical cyclogenesis radiation is most important. It is shown that all else being equal, a stronger initial vortex reduces the impact that radiation has on accelerating tropical cyclogenesis. We find that radiation’s primary role is to moisten the core of a disturbance through nocturnal differential radiative forcing between the disturbance and its cloud-free surroundings, and after sufficient moistening occurs over a deep layer and the winds are sufficiently strong at the surface, radiation no longer plays as significant a role in tropical cyclogenesis.
13
Budaev, Bair V., e David B. Bogy. "The role of EM wave polarization on radiative heat transfer across a nanoscale gap". Journal of Applied Physics 132, n.º 5 (7 de agosto de 2022): 054903. http://dx.doi.org/10.1063/5.0094382.
Texto completo da fonteResumo:
This work presents a novel study of radiative heat transfer between closely separated plates based on an extension of Planck’s spectrum of thermal radiations to systems with a steady heat flux. This extension together with electromagnetic wave theory is chosen specifically to avoid the commonly used so-called fluctuation dissipation theory, which is also limited to equilibrium systems. The spectrum of thermal radiation with a heat flux is described by the introduction of an analog of a chemical potential, which creates a bias toward the direction of heat transfer. This is the first comprehensive study of radiative heat transfer based on the generalization of Planck’s spectrum for systems with a heat flux, which eliminates contradictions arising when a heat flux is described in terms of the laws limited to equilibrium systems. The total heat flux is split into fluxes carried by waves with different frequencies, directions of propagation, and polarizations. This simplifies the analysis because due to the stochastic independence, the energy fluxes of such waves are additive, and this also reveals that the heat carrying capacity of radiation with the parallel polarization is significantly higher than that of the perpendicularly polarized radiation. This suggests that the rate of radiative heat transfer may be noticeably increased by the control of the polarization of thermal radiation.
14
Kolesnichenko, Aleksandr Vladimirovich. "Application to radiation acoustics of the Whitham method for analysing wave phenomena in magnetised plasma". Keldysh Institute Preprints, n.º 49 (2023): 1–35. http://dx.doi.org/10.20948/prepr-2023-49.
Texto completo da fonteResumo:
The exact governing equation of radiative acoustics in radiating grey gas is derived in this work, taking into account the influence of the transverse magnetic field. The radiative MHD is described by three equations of hydrodynamics and two equations of radiation momentum with extensive use of the formalism of radiative thermodynamics. In order to describe the propagation of linear radiative magneto-acoustic perturbation waves with scattering and attenuation, radiation-thermal dissipation conditions, radiation drag force, and magnetic force and Joule heat are introduced into these equations. The Eddington approximation is used, which allows us to study the modes of radiative magneto-hydrodynamic waves in two asymptotic cases - optically thin and thick gas. The exact governing equation derived in this paper allows, using the heuristic Whitham method, to obtain a set of approximate governing equations of lower order, each of which is part of a reliable approximation to the exact equation in a certain region of the independent time variable. The relatively simple form of such equations allows, without formally solving the full problem, to investigate the physical processes occurring in each radiative magneto-hydrodynamic linear travelling wave.
15
Aho-Mantila, L., F. Subba, M. Bernert, D. P. Coster, S. Wiesen, M. Wischmeier, X. Bonnin et al. "Predictions of radiation pattern and in–out asymmetries in the DEMO scrape-off layer using fluid neutrals". Nuclear Fusion 62, n.º 5 (2 de março de 2022): 056015. http://dx.doi.org/10.1088/1741-4326/ac4d62.
Texto completo da fonteResumo:
Abstract Strongly radiating and detached high-power discharges in present-day full-metal tokamaks have a characteristic radiation pattern involving condensation of radiation near the X-point, with significant radiative losses above the X-point. In contrast, Demonstration Fusion Power Plant (DEMO) divertor exhaust scoping studies using reduced physics models, including a fluid description for the neutrals, place the strongest radiation fronts in the divertor legs, near the separatrix. The present contribution studies sensitivity of the radiation pattern corresponding to maximal divertor impurity radiation to those physics models that are typically neglected in the simulations due to their computational expense: cross-field drifts, complex impurity models and kinetic neutrals. Model benchmarking is carried out in comparison to L-mode discharges, which are shown to feature both divertor and X-point radiation. The simulated plasma conditions with maximal divertor radiation have in–out asymmetries in the divertor legs and at the divertor entrance, and the asymmetries and the radiation patterns are observed to be sensitive to both cross-field drift effects and the neutral model. DEMO simulations, carried out using SOLPS-ITER, show an impact of cross-field drifts on the divertor asymmetries, but the impact is not large enough to move the radiation front from the divertor legs to regions above the X-point.
16
NITTA, HIDEO. "DIFFRACTED CHANNELING RADIATION AND OTHER COMPOUND RADIATION PROCESSES". International Journal of Modern Physics A 25, supp01 (junho de 2010): 128–35. http://dx.doi.org/10.1142/s0217751x10049979.
Texto completo da fonteResumo:
Radiations from a crystal irradiated with relativistic charged particles are reviewed with the emphasis on their fundamental processes. As their "compound processes" diffraction of both channeling radiation and coherent bremsstrahlung are considered. Coherent polarization radiation from neutral particles with magnetic moment is discussed within the framework of classical electrodynamics.
17
Golkarfard, Vahid, Seyyed Abdolreza Gandjalikhan Nassab e Amir Babak Ansari. "Simulation of Solid Particles in Combined Conduction, Convection and Radiation Gas Flow over a Backward-Facing Step in a Duct". Applied Mechanics and Materials 110-116 (outubro de 2011): 5276–82. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.5276.
Texto completo da fonteResumo:
A numerical simulation procedure for studying deposition of aerosol particles in a laminar convection flow of radiating gas over a backward-facing step including the effect of thermal force is developed. In the gas flow, all of the heat transfer mechanisms consisting of conduction, convection and radiation take place simultaneously. Behavior of solid particles is studied numerically based on an Eulerian–Lagrangian method. Two dimensional Navier-Stokes and energy equations are solved using CFD techniques, while the radiating transfer equation (RTE) is solved by discrete ordinate method (DOM) for calculating radiative heat flux distribution. The objective of this research is to study the effect of Reynolds number variation and also radiation on thermophoretic deposition of particles. Numerical results show a decrease in deposition percent by increasing in Reynolds number and the radiation effect is negligible. The results are compared with the existing experimental and numerical data and good agreement is found.
18
Blázquez, Miguel, Rüdiger Ortiz-Álvarez, Francisco Gasulla, Israel Pérez-Vargas e Sergio Pérez-Ortega. "Bacterial communities associated with an island radiation of lichen-forming fungi". PLOS ONE 19, n.º 3 (18 de março de 2024): e0298599. http://dx.doi.org/10.1371/journal.pone.0298599.
Texto completo da fonteResumo:
Evolutionary radiations are one of the most striking processes biologists have studied in islands. A radiation is often sparked by the appearance of ecological opportunity, which can originate in processes like trophic niche segregation or the evolution of key innovations. Another recently proposed mechanism is facilitation mediated by the bacterial communities associated with the radiating species. Here we explore the role of the bacterial communities in a radiation of lichen-forming fungi endemic to Macaronesia. Bacterial diversity was quantified by high throughput sequencing of the V1–V2 hyper-variable region of 172 specimens. We characterized the taxonomic and phylogenetic diversity of the bacterial communities associated with the different species, tested for compositional differences between these communities, carried out a functional prediction, explored the relative importance of different factors in bacterial community structure, searched for phylosymbiosis and tried to identify the origin of this pattern. The species of the radiation differed in the composition of their bacterial communities, which were mostly comprised of Alphaproteobacteria and Acidobacteriia, but not in the functionality of those communities. A phylosimbiotic pattern was detected, but it was probably caused by environmental filtering. These findings are congruent with the combined effect of secondary chemistry and mycobiont identity being the main driver of bacterial community structure. Altogether, our results suggest that the associated bacterial communities are not the radiation’s main driver. There is one possible exception, however, a species that has an abnormally diverse core microbiome and whose bacterial communities could be subject to a specific environmental filter at the functional level.
19
Ansaria, Amir, e Nassaba Gandjalikhan. "Forced convection of radiating gas over an inclined backward facing step using the blocked-off method". Thermal Science 17, n.º 3 (2013): 773–86. http://dx.doi.org/10.2298/tsci110112132a.
Texto completo da fonteResumo:
The present work investigates the laminar forced convection flow of a radiating gas over an inclined backward facing step (BFS) in a horizontal duct. The momentum and energy equations are solved numerically by the CFD techniques to obtain the velocity and temperature fields. Since, the twodimensional Cartesian coordinate system is used to solve the governing equations; the flow over inclined surface is simulated by considering the blocked-off region in regular grid. Discretized forms of the governing equations in the (x,y) plane are obtained by the control volume method and solved using the SIMPLE algorithm. The fluid is treated as a gray, absorbing, emitting and scattering medium. Therefore, all of the convection, conduction and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the radiative heat flux distribution inside the radiating medium. In the numerical results, effects of inclination angle, optical thickness, scattering albedo and the radiation-conduction parameter on the heat transfer behavior of the convection flow are investigated. This research work is a new one in which a combined convection-radiation thermal system with a complex flow geometry is simulate by efficient numerical techniques.
20
Zhang, Tianyu, Jiming Sun e Yi Yang. "A Numerical Study of Effects of Radiation on Deep Convective Warm Based Cumulus Cloud Development with a 3-D Radiative Transfer Model". Atmosphere 11, n.º 11 (2 de novembro de 2020): 1187. http://dx.doi.org/10.3390/atmos11111187.
Texto completo da fonteResumo:
The effects of radiation heating and cooling on cumulus cloud development have been the focus of considerable attention for many years. However, it is still not clear how radiation impacts cloud droplet growth. Since cloud inhomogeneity has a great influence on radiation transmission, we coupled the 3D atmospheric radiative transfer model using the spherical harmonic discrete ordinate method with WRF-LES, which can improve the simulation accuracy of the inhomogeneous effect of clouds on radiation compared with that of the 1D radiation method. The shortwave and longwave radiation fluxes for upward and downward directions were simulated with different solar zenith angles. The comparison of 1D and 3D radiative solvers for deep convective cloud cases shows that the 3D radiative solver provides an accurate structure of solar and thermal radiation characteristics and the spatial distribution field. The solar radiation heating is likely to increase perpendicular to the solar incidence direction. For longwave radiation, the cooling effect on the cloud top and the heating effect on the cloud base are both more intense in the 3D radiation model. This study focuses on 3D cloud-radiative interactions in an inhomogeneous cloud field in a large eddy simulation, and the results suggest that compared with the widely used 1D radiative solver in WRF, the 3D radiation model can provide a precise description of the radiation field in an inhomogeneous atmosphere.
21
Genner, Martin J., Benjamin P. Ngatunga, Semvua Mzighani, Alan Smith e George F. Turner. "Geographical ancestry of Lake Malawi's cichlid fish diversity". Biology Letters 11, n.º 6 (junho de 2015): 20150232. http://dx.doi.org/10.1098/rsbl.2015.0232.
Texto completo da fonteResumo:
The Lake Malawi haplochromine cichlid flock is one of the largest vertebrate adaptive radiations. The geographical source of the radiation has been assumed to be rivers to the south and east of Lake Malawi, where extant representatives of the flock are now present. Here, we provide mitochondrial DNA evidence suggesting the sister taxon to the Lake Malawi radiation is within the Great Ruaha river in Tanzania, north of Lake Malawi. Estimates of the time of divergence between the Lake Malawi flock and this riverine sister taxon range from 2.13 to 6.76 Ma, prior to origins of the current radiation 1.20–4.06 Ma. These results are congruent with evaluations of 2–3.75 Ma fossil material that suggest past faunal connections between Lake Malawi and the Ruaha. We propose that ancestors of the Malawi radiation became isolated within the catchment during Pliocene rifting that formed both Lake Malawi and the Kipengere/Livingstone mountain range, before colonizing rivers to the south and east of the lake region and radiating within the lake basin. Identification of this sister taxon allows tests of whether standing genetic diversity has predisposed Lake Malawi cichlids to rapid speciation and adaptive radiation.
22
Salim, Mohamed H., Sebastian Schubert, Jaroslav Resler, Pavel Krč, Björn Maronga, Farah Kanani-Sühring, Matthias Sühring e Christoph Schneider. "Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system". Geoscientific Model Development 15, n.º 1 (10 de janeiro de 2022): 145–71. http://dx.doi.org/10.5194/gmd-15-145-2022.
Texto completo da fonteResumo:
Abstract. Including radiative transfer processes within the urban canopy layer into microscale urban climate models (UCMs) is essential to obtain realistic model results. These processes include the interaction of buildings and vegetation with shortwave and longwave radiation, thermal emission, and radiation reflections. They contribute differently to the radiation budget of urban surfaces. Each process requires different computational resources and physical data for the urban elements. This study investigates how much detail modellers should include to parameterize radiative transfer in microscale building-resolving UCMs. To that end, we introduce a stepwise parameterization method to the Parallelized Large-eddy Simulation Model (PALM) system 6.0 to quantify individually the effects of the main radiative transfer processes on the radiation budget and on the flow field. We quantify numerical simulations of both simple and realistic urban configurations to identify the major and the minor effects of radiative transfer processes on the radiation budget. The study shows that processes such as surface and vegetation interaction with shortwave and longwave radiation will have major effects, while a process such as multiple reflections will have minor effects. The study also shows that radiative transfer processes within the canopy layer implicitly affect the incoming radiation since the radiative transfer model is coupled to the radiation model. The flow field changes considerably in response to the radiative transfer processes included in the model. The study identified those processes which are essentially needed to assure acceptable quality of the flow field. These processes are receiving radiation from atmosphere based on the sky-view factors, interaction of urban vegetation with radiation, radiative transfer among urban surfaces, and considering at least single reflection of radiation. Omitting any of these processes may lead to high uncertainties in the model results.
23
Boers, Reinout, Theo Brandsma e A. Pier Siebesma. "Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015)". Atmospheric Chemistry and Physics 17, n.º 13 (4 de julho de 2017): 8081–100. http://dx.doi.org/10.5194/acp-17-8081-2017.
Texto completo da fonteResumo:
Abstract. A 50-year hourly data set of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to the trend in yearly-averaged all-sky radiation (1.81 ± 1.07 W m−2 decade−1). Yearly-averaged clear-sky and cloud-base radiation data show large year-to-year fluctuations caused by yearly changes in the occurrence of clear and cloudy periods and cannot be used for trend analysis. Therefore, proxy clear-sky and cloud-base radiations were computed. In a proxy analysis hourly radiation data falling within a fractional cloudiness value are fitted by monotonic increasing functions of solar zenith angle and summed over all zenith angles occurring in a single year to produce an average. Stable trends can then be computed from the proxy radiation data. A functional expression is derived whereby the trend in proxy all-sky radiation is a linear combination of trends in fractional cloudiness, proxy clear-sky radiation and proxy cloud-base radiation. Trends (per decade) in fractional cloudiness, proxy clear-sky and proxy cloud-base radiation were, respectively, 0.0097 ± 0.0062, 2.78 ± 0.50 and 3.43 ± 1.17 W m−2. To add up to the all-sky radiation the three trends have weight factors, namely the difference between the mean cloud-base and clear-sky radiation, the clear-sky fraction and the fractional cloudiness, respectively. Our analysis clearly demonstrates that all three components contribute significantly to the observed trend in all-sky radiation. Radiative transfer calculations using the aerosol optical thickness derived from visibility observations indicate that aerosol–radiation interaction (ARI) is a strong candidate to explain the upward trend in the clear-sky radiation. Aerosol–cloud interaction (ACI) may have some impact on cloud-base radiation, but it is suggested that decadal changes in cloud thickness and synoptic-scale changes in cloud amount also play an important role.
24
Magee, John L. "Nonhomogeneous processes in radiation research: Radical diffusion models". Canadian Journal of Physics 68, n.º 9 (1 de setembro de 1990): 853–57. http://dx.doi.org/10.1139/p90-123.
Texto completo da fonteResumo:
Radiation research has come to mean investigations of the nature of penetrating radiations and their effects on the materials they traverse. The radiations themselves are fast charged particles (including atomic nuclei and electrons) and short wave length electromagnetic photons (X and γ rays). These radiations have the common property that they deposit their energy nonhomogeneously (in tracks) as they are stopped in matter. Chemically reactive species (excited molecules, ions, radicals, etc.) are created in the tracks. Irradiated systems are the earliest examples of systems recognized to be nonhomogeneous. The tracks formed by radiations develop by expansion and reaction of the newly created reactive species among themselves and with any molecules of the stopping medium. The radiation chemical yields of products depend on the nature of the track, which in turn depends on the radiation. Radiation chemists have been successful in the construction of models that describe track expansion and the prediction of radiation chemical yields. The development of this field, over the years, is reviewed.
25
STANTON, ROBERT. "Radiation Protection of Workers (Ionising Radiations)". Health Physics 55, n.º 6 (dezembro de 1988): 1017. http://dx.doi.org/10.1097/00004032-198812000-00026.
Texto completo da fonte
26
Hasan, Bismah, e Kamran Raza. "Dual Band Slotted Printed Circular Patch Antenna With Superstrate and EBG Structure for 5G Applications". January 2019 38, n.º 1 (1 de janeiro de 2019): 227–38. http://dx.doi.org/10.22581/muet1982.1901.19.
Texto completo da fonteResumo:
Slotted circular printed layered patch antenna is designed, simulated and fabricated for 5G (Fifth Generation) wireless communication applications. The antenna consists of slots in the main radiating circular patch element for miniaturizing the size of the radiating element and providing dual band radiation characteristics. The feed line is separated on bottom substrate layer with EBG (Electromagnetic Band-Gap) embedded for enhancing the gain characteristics of the antenna. Superstrate layer is also used for improving the gain of the antenna where the distance from the radiating antenna element is optimized for maximizing the impedance bandwidth and radiation characteristics. The feed realization and impedance matching of the radiating slotted circular patch antenna is done by inducing slot at the middle ground plane of the slot embedded circular patch antenna system. The proposed configuration provides power radiation gain values of more than 5 dB for the Ka band of communications, whereas the impedance bandwidth of the antenna is verified for the dual resonances at 27.5 and 28.5 GHz. Dual band radiation characteristics are attained by embedding and optimizing the slot length and width in the circular patch radiator element that is placed on the upper face of the substrate RT Rogers Duroid 5880 layer. The length of the microstrip feed line embedded in the lower layer of the substrate is optimized for providing required bandwidth characteristics for the dual frequency point radiations. The antenna configuration is designed, modeled and simulated in CST (Central Standard Time) Microwave studio. The antenna is fabricated and measured vs simulated frequency response, gain patterns and current density plots are presented for the verification of antenna operation in the desired frequency bands.
27
Zhao, De Chun, e Long Sheng Zhang. "Biological Effects of Electromagnetic Radiation and Protection". Applied Mechanics and Materials 513-517 (fevereiro de 2014): 3313–16. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.3313.
Texto completo da fonteResumo:
With the development of science and technology, electronic equipments are widely applied in society. Electronic equipments make life more convenient and efficient. However, a variety of harmful electromagnetic radiation is generated when the electronic equipment is working. The electromagnetic radiation not only affects the normal operation of other electronic device but also pollutes the environment survival for human. Furthermore, electromagnetic radiation is harm to human. Therefore, it is important to take measures to prevent various electromagnetic radiations. Firstly this paper introduces relevant knowledge of electromagnetic radiation and standards on electromagnetic radiation. Then, it analyses the biological effect of electromagnetic radiations according to the radiation distribution of cell-phone. Finally, it proposes protective measures based on the study of the biological effect.
28
Cisterna-Osorio, Pedro, Sergio Quijada-Vera, Daniela Ruiz-Duran, Rodrigo Peirano-Cuevas e Pamela Ortiz-Briones. "First Results: Innovative Solar Disinfection Technology for Treated Wastewater that Integrates Materiality, Geometry, and Reflective Panels". International Journal of Environmental Research and Public Health 17, n.º 18 (8 de setembro de 2020): 6523. http://dx.doi.org/10.3390/ijerph17186523.
Texto completo da fonteResumo:
Climate change is having drastic consequences in Chile. The lack of water in various regions is causing environmental impacts on ecosystems, including the decrease in the productive activities of rural economies and the deterioration in the quality of life of the inhabitants that occupy the affected physical spaces. In this paper, we propose a sustainable, low-cost treatment of wastewater and its reuse as an adaptation and mitigation policy, patented in 2019, that consists of a wastewater disinfection system based on solar energy. This system can work in both continuous and discontinuous modes. The water passes through a canal of reflective material in the continuous regime, and in the batch regime, the water remains in the canal. The panels are located parallel to the lateral faces of the canal. These panels concentrate the radiation in the canal through reflection. The trapezoidal geometry of the disinfectant canal deflects the radiation and reflects in the direction of the front walls of the canal, radiating what is returned and vice versa. The fraction of the radiation reflected outside the canal reaches the reflective side panels that return the radiation to the canal. The synergy of these three considerations increases the radiation in the canal area, augmenting the elimination of the bacterial load. In the trapezoidal reflective canal without panels, only 5% of the measured radiation exceeded the atmospheric radiation, eliminating 83% of the coliforms. The incorporation of panels surpassed the atmospheric radiation over 36% of the measured radiations, and the removal of coliforms exceeded 99.7%.
29
Nia, M. Foruzan, e S. A. Gandjalikhan Nassab. "Conjugate Heat Transfer Study of Combined Radiation and Forced Convection Turbulent Separated Flow". International Journal of Nonlinear Sciences and Numerical Simulation 18, n.º 1 (1 de fevereiro de 2017): 29–39. http://dx.doi.org/10.1515/ijnsns-2015-0134.
Texto completo da fonteResumo:
AbstractIn the current study, a numerical investigation of two-dimensional combined convection-radiation heat transfer of turbulent gas flow over a backward-facing step (BFS) in a horizontal rectangular duct is presented. The computational domain contains two different parts including gas flow and solid element that makes the problem as a conjugate one. The gas phase is considered to be a radiating media that can absorb, emit and scatter thermal radiation, where in solid phase, heat transfer takes place by conduction. The set of governing equations for gas flow is solved numerically using the CFD technique and the $$k - \varepsilon $$ model is employed for computation of turbulence fluctuations. To evaluate the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). Inside the solid phase, the conduction equation is solved to obtain the temperature distribution. The effects of conduction ratio, optical thickness, radiation-conduction parameter and albedo coefficient on heat transfer behavior of the system are carried out.
30
Moein Addini, M., e S. A. Gandjalikhan Nassab. "Combined Mixed Convection and Radiation Heat Transfer in an Obstacle Wall Mounted Lid-driven Cavity". International Journal of Nonlinear Sciences and Numerical Simulation 17, n.º 6 (29 de setembro de 2016): 277–89. http://dx.doi.org/10.1515/ijnsns-2015-0095.
Texto completo da fonteResumo:
AbstractThis paper presents a numerical investigation for laminar mixed convection flow of a radiating gas in a lid-driven cavity with a rectangular-shaped obstacle attached on the bottom wall. The vertical walls of the square cavity are assumed to be adiabatic, while other walls of cavity and obstacle are kept at constant temperature. The fluid is treated as a gray, absorbing, emitting and scattering medium. The governing differential equations consisting the continuity, momentum and energy are solved numerically by the computational fluid dynamics techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides convection and conduction, radiative heat transfer also takes place in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation is solved numerically by the discrete ordinate method. The streamline and isotherm plots and the distributions of convective, radiative and total Nusselt numbers along the bottom wall of cavity are presented. The effects of Richardson number, obstacle location, radiation–conduction parameter, optical thickness and albedo coefficient on the flow and temperature distributions are carried out. Comparison between the present numerical results with those obtained by other investigators in the cases of conduction–radiation and pure convection systems shows good consistencies.
31
Oreshkin, V. I., e E. V. Oreshkin. "Effect of the plasma self-radiation on the growth of thermal filamentation instabilities in imploding Z pinches". Plasma Physics and Controlled Fusion 63, n.º 12 (3 de novembro de 2021): 125013. http://dx.doi.org/10.1088/1361-6587/ac2af7.
Texto completo da fonteResumo:
Abstract The development of thermal filamentation (TF) instabilities in a current-carrying plasma shell under the action of the plasma self-radiation was analyzed in terms of a small perturbation theory. A stationary collisional radiative model was used to calculate the parameters of the bremsstrahlung, recombination radiation, and spectral line radiation. It has been shown that radiative losses can either enhance or weaken the growth of TF instabilities. The pattern of the effect is governed by the dependence of the energy lost by the plasma due to radiation, Q Rad, on the plasma temperature T. If Q Rad increases slower than ∼T, the radiative losses enhance TF instabilities. In the opposite case, that is when Q Rad increases faster than ∼T, the radiative losses lead to suppression of TF instabilities. When the energy lost due to radiation is greater than the Joule energy input, TF instabilities can be completely stabilized due to radiation. The plasma parameter ranges for which stabilization of TF instabilities may occur due to radiation have been found for aluminum and argon.
32
Stupakov, G. "Electromagnetic Radiation in Accelerator Physics". Reviews of Accelerator Science and Technology 03, n.º 01 (janeiro de 2010): 39–56. http://dx.doi.org/10.1142/s179362681000035x.
Texto completo da fonteResumo:
This article reviews some fundamental concepts and presents several recent techniques used for calculation of radiation in various environments. They include properties of longitudinal and transverse formation lengths of radiation, usage of the parabolic equation and the Kirchhoff diffraction integral in radiation, coherent radiation and fluctuations in the beam, and the radiative reaction force resulting from coherent radiation.
33
Liu, Hong, Li Zheng, Hong Jun Yang, Wei Yang e Yong Lin Zheng. "Spontaneous Radiation Energy of Current Filaments in GaAs Photoconductive Semiconductor Switches". Applied Mechanics and Materials 423-426 (setembro de 2013): 2659–62. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.2659.
Texto completo da fonteResumo:
The spontaneous radiation energy of the current filaments in high gain GaAs photoconductive semiconductor switches (PCSS) is quantificationally analyzed. The spontaneous radiation formula of the current filaments was derived. The concept of the distribution function of the radiation intensity dependent on radiation wavelength was first introduced in GaAs samples. The radiative recombination coefficients of four peak wavelengths were estimated by the statistical-physical method in high gain GaAs PCSS. Calculated according to the radiative recombination coefficient of 890 nm radiation, the spontaneous radiation energies are consistent with the experimental observations. This explains the observations about optical output energy versus filament current.
34
Koutsantoniou, Leela Elpida. "Algorithms and radiation dynamics for the vicinity of black holes". Astronomy & Astrophysics 657 (24 de dezembro de 2021): A32. http://dx.doi.org/10.1051/0004-6361/202140682.
Texto completo da fonteResumo:
We examine radiation and its effects on accretion disks orbiting astrophysical black holes. These disks are thermally radiating and can be geometrically and optically thin or thick. In this first paper of the series, we discuss the physics and the formulation required for this study. Subsequently, we construct and solve the relativistic radiative transfer equation, or find suitable solutions where that is not possible. We continue by presenting some of the accretion disks we considered for this work. We then describe the families of codes developed in order to study particle trajectories in strong gravity, calculate radiation forces exerted onto the disk material, and generate observation pictures of black hole systems at infinity. Furthermore, we also examine the veracity and accuracy of our work. Finally, we investigate how we can further use our results to estimate the black hole spin and the motion of disk material subjected to these radiation forces.
35
Sakher, Elfahem, Billel Smili, Mohamed Bououdina e Stefano Bellucci. "Structural Study of Nano-Clay and Its Effectiveness in Radiation Protection against X-rays". Nanomaterials 12, n.º 14 (7 de julho de 2022): 2332. http://dx.doi.org/10.3390/nano12142332.
Texto completo da fonteResumo:
With the increasing applications of nuclear technology, radiation protection has become very important especially for the environment and the personnel close to radiation sources. Natural clays can be used potentially for shielding the X-ray radiations. In this study, the correlation between structural parameters and radiation shielding performance of natural clay extracted from Algerian Sahara (Adrar, Reggan, and Timimoune) was investigated. Phase composition and structural parameters (lattice parameters, average crystallite size, and microstrain) were determined by the Rietveld refinements of X-ray diffraction patterns in the frame of HighScore Plus software. The obtained results showed that the studied clays are nanocrystalline (nano-clay) since the calculated crystallite size was ≈3 nm for the feldspar phase. FTIR spectra confirmed the presence of all phases already detected by XRD analysis besides Biotite (around the band at 3558 cm−1). The remaining bands corresponded to absorbed and adsorbed water (3432 cm−1 and 1629 cm−1, respectively) and atmospheric CO2 (2356 cm−1). The shielding properties (mass absorption coefficient—µ/ρ and radiative attenuation rate—RA) for (green-yellow, green, and red) clays of Adrar, (red, white, and white-red) clays of Reggan, and red clay of Timimoune at same energy level were examined. The results of clay samples were compared with each other. The obtained results indicated that the green clay of Adrar exhibited the superior radiation shielding, i.e., 99.8% and 243.4 cm2/g for radiative attenuation rate and mass absorption coefficient, respectively.
36
Atashafrooz, M., e SA Gandjalikhan Nassab. "Simulation of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a duct under bleeding condition". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, n.º 2 (17 de maio de 2012): 332–45. http://dx.doi.org/10.1177/0954406212447657.
Texto completo da fonteResumo:
This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.
37
Li, Shuqin, Qingguo Chang, Xiang Chen e Sicheng Liao. "Research on Short Term Prediction Algorithm for Freeway Pavement Ice". Academic Journal of Science and Technology 5, n.º 3 (23 de abril de 2023): 90–92. http://dx.doi.org/10.54097/ajst.v5i3.7783.
Texto completo da fonteResumo:
This article focuses on the short-term prediction algorithm for ice condensation on highway pavement. Solar radiation, ground long wave radiation, and atmospheric inverse radiation are the main factors affecting road surface temperature changes. According to the principle of radiation heat transfer, there is a radiation balance relationship among these three factors. Therefore, based on the balance relationship between these three radiations and the physical heat formula, this article designs a short-term prediction algorithm for road icing. Based on the basic theory of radiation heat transfer, the energy balance between solar shortwave radiation, atmospheric inverse radiation, and ground longwave radiation is calculated to predict the temperature of highway road surfaces.
38
Stroud, James T., e Jonathan B. Losos. "Bridging the Process-Pattern Divide to Understand the Origins and Early Stages of Adaptive Radiation: A Review of Approaches With Insights From Studies of Anolis Lizards". Journal of Heredity 111, n.º 1 (27 de novembro de 2019): 33–42. http://dx.doi.org/10.1093/jhered/esz055.
Texto completo da fonteResumo:
Abstract Understanding the origins and early stages of diversification is one of the most elusive tasks in adaptive radiation research. Classical approaches, which aim to infer past processes from present-day patterns of biological diversity, are fraught with difficulties and assumptions. An alternative approach has been to study young clades of relatively few species, which may represent the putative early stages of adaptive radiation. However, it is difficult to predict whether those groups will ever reach the ecological and morphological disparity observed in the sorts of clades usually referred to as adaptive radiations, thereby making their utility in informing the early stages of such radiations uncertain. Caribbean Anolis lizards are a textbook example of an adaptive radiation; anoles have diversified independently on each of the 4 islands in the Greater Antilles, producing replicated radiations of phenotypically diverse species. However, the underlying processes that drove these radiations occurred 30–65 million years ago and so are unobservable, rendering major questions about how these radiations came to be difficult to tackle. What did the ancestral species of the anole radiation look like? How did new species arise? What processes drove adaptive diversification? Here, we review what we have learned about the cryptic early stages of adaptive radiation from studies of Anolis lizards, and how these studies have attempted to bridge the process-pattern divide of adaptive radiation research. Despite decades of research, however, fundamental questions linking eco-evolutionary processes to macroevolutionary patterns in anoles remain difficult to answer.
39
Gillespie, Rosemary G., Gordon M. Bennett, Luc De Meester, Jeffrey L. Feder, Robert C. Fleischer, Luke J. Harmon, Andrew P. Hendry et al. "Comparing Adaptive Radiations Across Space, Time, and Taxa". Journal of Heredity 111, n.º 1 (janeiro de 2020): 1–20. http://dx.doi.org/10.1093/jhered/esz064.
Texto completo da fonteResumo:
Abstract Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.
40
Kolesnichenko, A. V. "Jeans Instability of an Astrophysical Self-Gravitating Medium in the Presence of High Radiation Pressure and Diffuse Radiative Transfer". Астрономический вестник 57, n.º 3 (1 de maio de 2023): 262–74. http://dx.doi.org/10.31857/s0320930x23030040.
Texto completo da fonteResumo:
Within the problem of modeling the evolution of a protostellar disk, a discussion is presented on the effect of radiation on the Jeans gravitational instability for a self-gravitating optically thick (for intrinsic infrared radiation) gas-and-dust medium, taking into account the influence of radiation pressure perturbations and radiative diffusion transfer on the critical wavelength. Two radiative diffusion approximations are considered: the case of perfect thermal equilibrium with the same temperature of matter and radiation and the case of the time dependence of the radiation field with an energy separation between radiation and matter. An analysis of the normal regime of modes is used to derive dispersion relations, which enable the derivation of modifications of the classical Jeans instability criterion under the influence of radiation pressure and radiation diffusion. In particular, it is shown that, in contrast to the system’s local thermodynamic equilibrium, where the acoustic velocity of perturbed gas propagates with the isothermal speed of sound, in the case of different temperatures of radiation and gas, the perturbing wave propagates with the adiabatic speed of sound in gas. The results obtained are aimed at solving the problem of gravitational instability of individual massive protostellar disks or self-gravitating radiative media characterized by large optical depths for their dust-transformed intrinsic infrared radiation.
41
Ruzmaikin, Alexander, Hartmut H. Aumann e Jonathan H. Jiang. "Interhemispheric Variability of Earth’s Radiation". Journal of the Atmospheric Sciences 72, n.º 12 (19 de novembro de 2015): 4615–28. http://dx.doi.org/10.1175/jas-d-15-0106.1.
Texto completo da fonteResumo:
Abstract The variability of interhemispheric symmetry of Earth’s energy serves as an independent indicator of climate change. The analysis of updated data obtained from satellite measurements at the top of the atmosphere (TOA) shows that in accord with Earth’s orbital requirements the annually averaged incident solar radiation is the same in the Northern and Southern Hemispheres, the annual mean of the reflected shortwave radiation is almost north–south symmetric, and the annual mean of the outgoing longwave radiation is larger in the Northern Hemisphere by 1.4 W m−2. These mean radiations systematically differ from the mean radiations found from the numerical atmospheric models that participated in the Coupled Model Intercomparison Project phase 5 (CMIP5). The hemispheric differences of the TOA radiations vary on the annual and interannual time scales. The multidecadal variability in Earth’s north–south temperature difference reveals a similarity of trends in both hemispheres. The Atlantic meridional transport (in contrast to the Pacific meridional transport) is found to be coherent with the interhemispheric ocean heat content (OHC) difference on decadal and multidecadal time scales, indicating a critical role of the Atlantic in the interhemispheric energy balance change.
42
Tajima, Y., e J. Fukue. "9.17. Accretion disk winds driven by the disk radiation field under radiation drag". Symposium - International Astronomical Union 184 (1998): 415–16. http://dx.doi.org/10.1017/s0074180900085442.
Texto completo da fonteResumo:
The radiative winds from a geometrically thin accretion disk are studied. The effect of radiation drag which causes in the intense radiation fields around the accretion disk is examined recently. Then, we numerically consider the radiatively-accelerated accretion-disk winds which consist of ionized gas particles, taking into account radiation drag of the order ofv/c.
43
Choi, Sung-Jin, Joon-Bum Jee, Kyu-Tae Lee e Il-Sung Zo. "Analyzing the Improvement Effect of the k-Distribution Method on the Radiation Parameterization for WRF Model". Atmosphere 15, n.º 7 (30 de junho de 2024): 796. http://dx.doi.org/10.3390/atmos15070796.
Texto completo da fonteResumo:
To address the need for the accurate parameterization of radiative absorption by gasses (for predicting atmospheric warming), Chou et al. developed a new k-distribution method. In this study, we compared the improved k-distribution method (hereinafter referred to as the NEW method) with the New Goddard radiation schemes (hereinafter referred to as the OLD method) for the WRF (the weather research and forecasting) model. The results of radiative flux calculations by the NEW and OLD methods of k-distribution using the New Goddard Radiation Scheme were compared with the results of the line-by-line (LBL) method, and the results showed that the radiative flux calculated by the NEW was accurate to within 1.00 Wm−2 with respect to the LBL, while the OLD showed large differences at altitudes above the upper troposphere and near the surface. Therefore, in this study, we selected clear-sky and cloudy-day conditions and compared the weather elements prediction results of WRF using the NEW and OLD methods. For the clear-sky days, the downward shortwave radiation at the surface and the temperature at 2 m above the surface (hereinafter referred to as T2) over land and ocean were reversed in sign due to the highly sensitive absorption coefficients of gasses. For cloudy days, the absorption effect by gasses harmonized with the scattering effect induced by cloud droplets; the differences in the shortwave and longwave radiations and radiative heating rate between the NEW and OLD methods were obvious. Thus, it was analyzed that the proposed NEW method could lead to significant improvements in forecasting weather elements.
44
Shahid, Saman, Asma Majeed, Rana Aatif Siddique, Khalid Masood e Shahid Ali. "Lifetime Risk of Radiation Induced Severe Hereditary Stochastic (SHS) Effects in Medical Radiation Personnel". Pakistan Journal of Medical and Health Sciences 15, n.º 5 (30 de maio de 2021): 1105–7. http://dx.doi.org/10.53350/pjmhs211551105.
Texto completo da fonteResumo:
Background: Hereditary risk assessments in medical radiation workers must be accentuated as a precaution against genetic diseases. Ionizing radiations can induce hereditary or genetic radiation effects. Aim: To evaluate the lifetime risk of severe hereditary stochastic (SHS) effects in INMOL’s medical radiation personnel. Methods: The determination of the ‘whole-body’ effective doses was performed by ‘dose assessment algorithm’. We adopted the procedure described by ICRP for the assessment of lifetime severe hereditary annual risks by using ‘nominal probability coefficient’. Results: The AAEDs were between 1.41-1.79 mSv (in NM), 1.07-1.43 mSv (in RT) and 1.21-1.70 mSv (in RD) during 2014-2018. A declining trend is observed in AAED values in five consecutive years, due to improvements in radiation protection and safety measures. The risks of severe hereditary effects were also decreased from 2014-2018. The SHS risk was decreased from 5.012×10-4 to 3.948 ×10-4 in NM, 4.004×10-4 to 2.996×10-4 in RT and 4.76×10-4 to 3.388×10-4 in DR department. Conclusion: This study is emphasizing towards evaluating risks of hereditary effects from chronic exposure of radiations in occupational workers to avoid further late genetic complications. Such quantitative indicators would be useful in comparing other lifetime death risks from other harmful substances. Keywords: Hereditary Stochastic Effects; Annual Average Effective Doses; Nominal Probability Coefficient; Medical Radiation; Occupational Radiation Risk Assessments
45
Perovich, Donald K. "Sunlight, clouds, sea ice, albedo, and the radiative budget: the umbrella versus the blanket". Cryosphere 12, n.º 6 (27 de junho de 2018): 2159–65. http://dx.doi.org/10.5194/tc-12-2159-2018.
Texto completo da fonteResumo:
Abstract. The surface radiation budget of the Arctic Ocean plays a central role in summer ice melt and is governed by clouds and surface albedo. I calculated the net radiation flux for a range of albedos under sunny and cloudy skies and determined the break-even value, where the net radiation is the same for cloudy and sunny skies. Break-even albedos range from 0.30 in September to 0.58 in July. For snow-covered or bare ice, sunny skies always result in less radiative heat input. In contrast, leads always have, and ponds usually have, more radiative input under sunny skies than cloudy skies. Snow-covered ice has a net radiation flux that is negative or near zero under sunny skies, resulting in radiative cooling. Areally averaged albedos for sea ice in July result in a smaller net radiation flux under cloudy skies. For May, June, August, and September, the net radiation is smaller under sunny skies.
46
Shan, Shiquan, e Zhijun Zhou. "Second Law Analysis of Spectral Radiative Transfer and Calculation in One-Dimensional Furnace Cases". Entropy 21, n.º 5 (2 de maio de 2019): 461. http://dx.doi.org/10.3390/e21050461.
Texto completo da fonteResumo:
This study combines the radiation transfer process with the thermodynamic second law to achieve more accurate results for the energy quality and its variability in the spectral radiation transfer process. First, the core ideas of the monochromatic photon exergy theory based on the equivalent temperature and the infinite-staged Carnot model are reviewed and discussed. Next, this theory is combined with the radiation transfer equation and thus the spectral radiative entropy and the radiative exergy transfer equations are established and verified based on the second law of thermodynamics. Finally, one-dimensional furnace case calculations are performed to determine the applicability to engineering applications. It is found that the distribution and variability of the spectral radiative exergy flux in the radiation transfer process can be obtained using numerical calculations and the scatter media could slightly improve the proportion of short-wavelength radiative exergy during the radiation transfer process. This has application value for research on flame energy spectrum-splitting conversion systems.
47
Trabing, Benjamin C., Michael M. Bell e Bonnie R. Brown. "Impacts of Radiation and Upper-Tropospheric Temperatures on Tropical Cyclone Structure and Intensity". Journal of the Atmospheric Sciences 76, n.º 1 (28 de dezembro de 2018): 135–53. http://dx.doi.org/10.1175/jas-d-18-0165.1.
Texto completo da fonteResumo:
Abstract Potential intensity theory predicts that the upper-tropospheric temperature acts as an important constraint on tropical cyclone (TC) intensity. The physical mechanisms through which the upper troposphere impacts TC intensity and structure have not been fully explored, however, due in part to limited observations and the complex interactions between clouds, radiation, and TC dynamics. In this study, idealized Weather Research and Forecasting Model ensembles initialized with a combination of three different tropopause temperatures and with no radiation, longwave radiation only, and full diurnal radiation are used to examine the physical mechanisms in the TC–upper-tropospheric temperature relationship on weather time scales. Simulated TC intensity and structure are strongly sensitive to colder tropopause temperatures using only longwave radiation, but are less sensitive using full radiation and no radiation. Colder tropopause temperatures result in deeper convection and increased ice mass aloft in all cases, but are more intense only when radiation was included. Deeper convection leads to increased local longwave cooling rates but reduced top-of-the-atmosphere outgoing longwave radiation, such that the total radiative heat sink is reduced from a Carnot engine perspective in stronger storms. We hypothesize that a balanced response in the secondary circulation described by the Eliassen equation arises from upper-troposphere radiative cooling anomalies that lead to stronger tangential winds. The results of this study further suggest that radiation and cloud–radiative feedbacks have important impacts on weather time scales.
48
Bratman, Vladimir, Yuri Lurie, Yuliya Oparina e Andrey Savilov. "Capabilities of Terahertz Cyclotron and Undulator Radiation from Short Ultrarelativistic Electron Bunches". Instruments 3, n.º 4 (11 de outubro de 2019): 55. http://dx.doi.org/10.3390/instruments3040055.
Texto completo da fonteResumo:
Mechanisms of coherent spontaneous cyclotron and undulator radiations of short dense bunches, in which electrons move along the same stationary helical trajectories, but have different dynamic properties, have been compared in detail. The results are based on the simplest 1D model in the form of a plane consisting of uniformly distributed synchronously moving and in-phase emitting particles, as well as numerical 3D codes developed to study the dynamics of bunches in waveguides taking into account the effects of the radiation and spatial charge fields. For cyclotron radiation under group synchronism conditions, the Coulomb expansion of a bunch occurs along the surface of a constant wave phase with the formation of an effectively radiating coherent structure. A significantly higher radiation frequency, but with a lower efficiency, can be obtained in the regime of simultaneous excitation of high-frequency (autoresonant) and low-frequency waves; in the field of the latter, stabilization of the bunch phase size can be achieved. Such a two-wave generation is much more efficient when the bunches radiate in the combined undulator and strong guiding magnetic fields under conditions of the negative mass instability, when both the Coulomb interaction of the particles and the radiation field stabilize the longitudinal size of the bunch.
49
Cheng, Tien-Chun, Chung-Jen Tseng, Ling-Chia Weng e Shih-Kuo Wu. "Combined natural convection and radiation with temperature-dependent properties". Thermal Science 22, n.º 2 (2018): 921–30. http://dx.doi.org/10.2298/tsci160225171c.
Texto completo da fonteResumo:
This paper investigates the effects of temperature dependence of radiative properties of a medium on radiation and natural convection interaction in a rectangular enclosure. The radiative transfer equation is solved using the discrete ordinates method, and the momentum, continuity, and energy equations are solved by the finite volume method. Effects of the conduction-to-radiation parameter, Rayleigh number, and optical thickness are discussed. Results show that temperature dependence of radiative properties affects the temperature gradient, and hence the energy transport even in relatively weak radiation condition. On the other hand, temperature dependence of radiative properties has relatively insignificant effects on convection characteristics, even though it does affect the way that energy transfers into the system. As conduction-to-radiation parameter is decreased or Rayleigh number is increased, the effects of temperature dependence of radiative properties become more significant.
50
Rosida, NFN, e Indah Susanti. "PENGARUH AEROSOL TERHADAP FLUKS RADIASI NETO DI LAPISAN ATAS ATMOSFER DAN DI PERMUKAAN BERDASAR DATA SATELIT [INFLUENCE OF AEROSOL ON NET RADIATION FLUX AT THE TOP OF ATMOSPHERE AND SURFACE BASED ON SATELLITE]". Jurnal Sains Dirgantara 14, n.º 2 (21 de julho de 2017): 27. http://dx.doi.org/10.30536/j.jsd.2016.v14.a2444.
Texto completo da fonteResumo:
The direct effects of aerosols on radiation budget in Indonesia have been analyzed based on radiation flux net data from the Clouds and the Earth's Radiant Energy System (CERES) instrument and aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra. Radiation budget calculated including short wave and long-wave radiation. Data from March 2000 until February 2010, processed using Grads version 2 to obtain aerosol radiative forcing value. Net radiation in clean sky, estimated using slope method. The analysis showed high temporal variation of aerosols density in the atmosphere with a value AODmax> 2, which generally causes decreases net radiation flux, so providing a cooling effect. The influence of aerosols on the net radiation flux can be very clearly seen in the case of forest fires. AOD in 2006 increased and caused radiation flux anomalies ranging from -9 watt/m-2 to -14 watts/m-2, with the largest decline occurred in the surface. From all the data period, aerosol radiative forcing at TOA level (ARFTOA) on Indonesia was -0.49 watt/m-2 and aerosol radiative forcing at the surface level (ARFSurf) on Indonesia was -17.72 watt/m-2, that influence to the Indonesian climate condition.