Littérature scientifique sur le sujet « Radiations spatiales »
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Articles de revues sur le sujet "Radiations spatiales"
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Kitov, B. I. « Fluorescence of anisotropic primary X-ray radiation ». Аналитика и контроль 26, no 1 (2022) : 6–12. http://dx.doi.org/10.15826/analitika.2022.26.1.002.
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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.
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Schwarz, Benjamin, Matthias Sammer, Nicole Matejka, Sarah Rudigkeit et 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, no 1 (9 mai 2023) : 1–8. http://dx.doi.org/10.46439/radiation.2.006.
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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.
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Volosyuk, V. K., S. S. Zhyla, V. V. Pavlikov, A. D. Abramov et V. G. Yakovlev. « Оptimal algorithm of radio brightness estimation in the spatial distributed radiometric sys-tems ». Radiotekhnika, no 191 (22 décembre 2017) : 143–49. http://dx.doi.org/10.30837/rt.2017.4.191.13.
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Optimization of processing of radio thermal radiation noise processes in multichannel spatially-distributed radiometric systems is performed. The received algorithms applicable in the systems of aperture synthesis are received within the maximum likelihood method in the assumption that spectral brightness of radiation within the frequency band of the receiver is constant, but as the image of a radiating object it depends on spatial (angular) coordinates. Feature of the solved tasks consists in using spectral VF -transforms which do not require execution of the spatiotemporal band-limitedness (quasi monochromatic approximation) condition and make it possible to solve the problem of synthesis of algorithms for processing wideband and ultra wideband processes.
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Karabekova, D. Zh. « VARIATION OF SPATIALLY HETEROGENEOUS RADIATION BY COORDINATE-SENSITIVE RECEIVER ». Eurasian Physical Technical Journal 17, no 1 (juin 2020) : 113–18. http://dx.doi.org/10.31489/2020no1/113-118.
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Bratman, Vladimir, Yuri Lurie, Yuliya Oparina et Andrey Savilov. « Capabilities of Terahertz Cyclotron and Undulator Radiation from Short Ultrarelativistic Electron Bunches ». Instruments 3, no 4 (11 octobre 2019) : 55. http://dx.doi.org/10.3390/instruments3040055.
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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.
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Mordachev, V. I. « Assessment of the Contribution of Radiations of User Equipment to the Anthropogenic Electromagnetic Background Created by Mobile (Cellular) Communications ». Doklady BGUIR 21, no 5 (26 octobre 2023) : 50–58. http://dx.doi.org/10.35596/1729-7648-2023-21-5-50-58.
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The declared increase in spatial density of user (terminal, peripheral, etc.) radiating equipment (UE) of mobile communications up to 0.1 UE/m2 in 4G (LTE) networks, up to 1.0 UE/m2 in 5G (NR) networks and up to 10 UE/m2 in promising 6G networks may cause an unacceptable increase in electromagnetic background and in corresponding forced risks to public health. The paper proposes a method for assessing the contribution of UE radiations to the level of anthropogenic electromagnetic background created by mobile communications. This method is based on the analysis of the electromagnetic loading on the area created by stationary and mobile radiation sources of mobile communications and determined by the area density of mobile traffic, its asymmetry in downlink and uplink data transmission, the degree of UE concentration in the observation point vicinity, the radio channels spectral efficiency, the size of base stations service areas and other characteristics. The calculated data are given, indicating that in places of UE concentration, the component of electromagnetic background formed by UE radiations may be predominant, many times exceeding the contribution of base station radiations, and determining the actual level of forced risks to public health, which requires consideration in the system of their hygienic rationing.
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Kang, Sinkyu, Sungwoo Kim et Dowon Lee. « Spatial and temporal patterns of solar radiation based on topography and air temperature ». Canadian Journal of Forest Research 32, no 3 (1 mars 2002) : 487–97. http://dx.doi.org/10.1139/x01-221.
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Incident solar radiation is a driving force for many ecological and hydrological processes. For this study, we developed TopoRad, a new radiation model, to describe spatial and temporal patterns of daily radiation based on topography and daily temperature regimes. The model was applied to the Mount Jumbong Forest, located in the mid-eastern area of the Korean peninsula; and the model calculations were evaluated by varying the spatial scales of the digital elevation models (DEMs). In the TopoRad, a clearness index was used to calculate global radiation on a horizontal surface and to partition direct and diffuse radiation. Topographic corrections were separately calculated for each direct and diffuse radiation, using daily topographic modifiers calculated from a DEM. TopoRad predicted daily global radiation of five weather stations with a mean absolute error of 3.1 MJ·m2·day1 and a mean bias of 0.3 MJ·m2·day1. In the spatial application for Mount Jumbong Forest, distinctively different patterns between direct and diffuse radiations were found where direct radiation (5.2 MJ·m2·day1) had more influence than diffuse radiation (4.6 MJ·m2·day1) on annual mean daily radiation. When the scaling effect was inspected across different spatial resolutions, the predicted global radiation was nonlinearly related to spatial resolutions. As the spatial resolution became more coarse, the predicted radiation decreased for south-facing slopes and increased for north-facing slopes, indicating that the predictions from the models cannot be generalized for gradients. TopoRad is better suited to predict daily radiation in rugged landscapes where fine-scale prediction is required.
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Linder, Hans Peter. « Plant species radiations : where, when, why ? » Philosophical Transactions of the Royal Society B : Biological Sciences 363, no 1506 (25 juin 2008) : 3097–105. http://dx.doi.org/10.1098/rstb.2008.0075.
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The spatial and temporal patterns of plant species radiations are largely unknown. I used a nonlinear regression to estimate speciation and extinction rates from all relevant dated clades. Both are surprisingly high. A high species richness can be the result of either little extinction, thus preserving the diversity that dates from older radiations (a ‘mature radiation’), or a ‘recent and rapid radiation’. The analysis of radiations from different regions (Andes, New Zealand, Australia, southwest Africa, tropics and Eurasia) revealed that the diversity of Australia may be largely the result of mature radiations. This is in sharp contrast to New Zealand, where the flora appears to be largely the result of recent and rapid radiations. Mature radiations are characteristic of regions that have been climatically and geologically stable throughout the Neogene, whereas recent and rapid radiations are more typical of younger (Pliocene) environments. The hyperdiverse Cape and Neotropical floras are the result of the combinations of mature as well as recent and rapid radiations. Both the areas contain stable environments (the Amazon basin and the Cape Fold Mountains) as well as dynamic landscapes (the Andes and the South African west coast). The evolution of diversity can only be understood in the context of the local environment.
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KAWAMURA, TOHRU, KAZUHIKO HORIOKA et FUMIHIRO KOIKE. « Potential of Kα radiation by energetic ionic particles for high energy density plasma diagnostics ». Laser and Particle Beams 24, no 2 (juin 2006) : 261–67. http://dx.doi.org/10.1017/s0263034606060393.
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In this paper, potential of diagnostics with the use ofKα radiation for an energy deposition process from an intense ion-beam to background plasma is considered quantitatively.Kα radiation is a good candidate for the purpose. The wavelength ofKα radiation is varied according to the charge state of an emitter atom, and the diagnostics spatially resolved with radiations from various kinds of charge states can give us a profile of plasma temperature in a target material. For the calculation ofKα yield, an atomic population kinetics code is developed, and the result shows thatKα radiation has potential to get information of a plasma profile heated by an intense ion-beam.
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Essery, Richard, Peter Bunting, Aled Rowlands, Nick Rutter, Janet Hardy, Rae Melloh, Tim Link, Danny Marks et John Pomeroy. « Radiative Transfer Modeling of a Coniferous Canopy Characterized by Airborne Remote Sensing ». Journal of Hydrometeorology 9, no 2 (1 avril 2008) : 228–41. http://dx.doi.org/10.1175/2007jhm870.1.
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Abstract Solar radiation beneath a forest canopy can have large spatial variations, but this is frequently neglected in radiative transfer models for large-scale applications. To explicitly model spatial variations in subcanopy radiation, maps of canopy structure are required. Aerial photography and airborne laser scanning are used to map tree locations, heights, and crown diameters for a lodgepole pine forest in Colorado as inputs to a spatially explicit radiative transfer model. Statistics of subcanopy radiation simulated by the model are compared with measurements from radiometer arrays, and scaling of spatial statistics with temporal averaging and array size is discussed. Efficient parameterizations for spatial averages and standard deviations of subcanopy radiation are developed using parameters that can be obtained from the model or hemispherical photography.
Thèses sur le sujet "Radiations spatiales"
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Kündig, Jamil. « Cellules solaires en couches minces de silicium : résistance aux radiations et applications spatiales / ». [S.l.] : [s.n.], 2003. http://library.epfl.ch/theses/?nr=2874.
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Pacaud, Rémi. « Étude et modélisation numérique de l’effet des radiations spatiales sur l’évolution des propriétés physiques et électriques des matériaux embarqués ». Thesis, Toulouse, ISAE, 2018. http://www.theses.fr/2018ESAE0039/document.
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Ma thèse consiste à établir un modèle numérique 1D qui permettra d'approfondir nos connaissances dans la compréhension des mécanismes physiques régissant le transport de charges dans les matériaux diélectriques comme le Kapton ou le Téflon soumis à des irradiations hauts-flux/hautes-énergies. Ce modèle est implémenté sous l'environnement Eclipse. Ensuite, les résultats numériques seront comparés aux résultats expérimentaux pour contrôler le bon fonctionnement du code une dimension (1D). A plus ou moins long terme, cette thèse permettra de déboucher sur une bonne compréhension du transport de charges dans les polymères embarqués en environnement spatial, ce qui permettra de comprendre l'origine des décharges électriques qui se produisent sur les panneaux solaires des satellites utilisés en orbite géostationnaireI have to establish a 1D numerical model that enables to better understand the physical mechanisms that steer charge transport in dielectric materials such as Kapton or Teflon under high fluxes and high energy electron beams. This model is implemented in Java under the Eclipse environment. Then, numerical results will be compared to experimental results in order to verify whether the 1D model is functional or not. In the near future, this phd will allow to better understand charge transport in satellite embedded polymers. We will then be able to understand the origin of electric discharges that occur on satellite solar panels used in geostationary orbit
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Pedroza, Guillaume. « Evaluation de la fiabilité de composants optoélectroniques pour des applications spatiales : apport des caractérisations et des modélisations électro-optiques ». Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14470/document.
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Ce mémoire présente les résultats de travaux portant sur l’analyse de la fiabilité de diodes laser de pompe émettant à 980 nm et de photodiodes InGaAs pour des applications spatiales. La sévérité de l’environnement spatial (vide, radiations, contraintes thermomécaniques) impose d’évaluer la robustesse de ces deux technologies qui ont été spécialement conçues pour des applications de télécommunications sous-marines. L’objectif de ce mémoire est donc de proposer une méthodologie d’évaluation de la fiabilité en s’appuyant la caractérisation électro-optique, l’analyse physico-chimique et la modélisation. Les diodes laser ont été vieillies sous ultravide (pression de 10-7 mbar) pendant 5000h sous 800 mA et 60°C. Certains composants, dont l’herméticité du boîtier a été volontairement rompue, ont présenté des défaillances de type COD (Catastrophic Optical Damage). Les caractéristiques des composants, dont le boîtier est resté hermétique, n’ont cependant pas dérivé. Après avoir modélisé les caractéristiques électriques du composant, mené des analyses physiques (AFM, MEB, MET, cathodoluminescence et ToF-SIMS) et calculé la variation de la pression à l’intérieur du boîtier, nous avons estimé la durée de vie du composant fonctionnant sous ultravide à 26 ans.Les photodiodes ont été irradiées par des protons d’énergie comprise entre 30 et 190 MeV sous une fluence comprise entre 5.1010 et 1012 p/cm², entrainant une augmentation du courant d’obscurité de trois décades. La modélisation du courant d’obscurité a permis d’estimer la durée de vie du composant en environnement spatial à 15 ans.Ces travaux ont également contribué à mettre en évidence des mécanismes de dégradation peu documentés (COD sous vide, difficulté d’ajustement avec le NIEL, dégradation du réseau de Bragg exposé aux rayonnements ionisants), ce qui permet de mieux appréhender le comportement des diodes laser et des photodiodes exposées à l’environnement spatialIn this work, the reliability of 980 nm pump laser diode and InGaAs photodiode modules has been estimated for space applications. The space environment is particularly harsh (vacuum, radiation, thermal and mechanical stresses) for these electro-optical devices, which were designed for long-haul submerged telecommunication applications. The main objective of this thesis is to provide a guideline for the space evaluation of optoelectronic devices, using characterization, physical analysis and modeling.Eight laser diodes were aged in vacuum (10-7 mbar) during 5000h, at 60°C and 800 mA bias current. The hermeticity of four of them was voluntarily broken to simulate a long term vacuum exposition. Three of four non-hermetic devices failed during the ageing, because of COD (Catastrophic Optical Damage) whereas the electro-optical characteristics of hermetic devices remained unchanged. The MTBF of laser diodes operating in vacuum was estimated to 26 years, by means of modeling (electro-optics and pressure) and physical analyses (AFM, SEM, TEM, cathodoluminescence, ToF-SIMS).InGaAs photodiodes were irradiated by protons, with energies ranging from 30 to 190 MeV and fluences ranging from 5.1010 to 1012 p/cm². The dark current increased by three decades after irradiation. The photodiode MTBF was then estimating to 15 years using dark current modeling.This study also permitted to show up almost new failure mechanisms (COD under vacuum, NIEL scaling errors in InGaAs, Bragg grating degradation under ionizing radiation and its effects on laser diode stabilization), which could contribute to the space evaluation of laser diodes and photodiodes for future missions
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Duchez, Jean-Bernard. « Étude du noircissement dans les fibres optiques dopées Ytterbium : interaction entre photo- et radio-noircissement ». Thesis, Nice, 2015. http://www.theses.fr/2015NICE4029.
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Cette thèse traite des dégradations induites par la pompe (photo-noircissement) et les radiations ionisantes externes (radio-noircissement) dans les fibres optiques en silice dopées ytterbium (FDY) utilisées en environnement sévère. Au travers de caractérisations expérimentales et de modélisations inédites, elle analyse leur interaction et en tire les conséquences quant à la tenue des FDY aux radiations sous pompe. La première partie porte sur l’identification des défauts induits (centres colorés) et leurs mécanismes de formation/guérison. Elle s’appuie sur un ensemble de caractérisations post-irradiation (RPE, ARI, TL) réalisées sur des échantillons de préformes et sur leur corrélation originale (guérison thermique, couplage TL et ARI). L’étude systématique en fonction de la composition met en évidence l’influence des co-dopants (Al, Ce) sur la capture des charges libérées lors des processus d’ionisation. La seconde partie analyse le noircissement se développant sous l’effet simultané de la pompe et de l’irradiation ionisante. A partir d’un banc de mesures autorisant le suivi de la dégradation en temps réel, on montre que photo- et radio-noircissements résultent des mêmes centres colorés blanchis par la pompe. Ce résultat, ajouté aux mécanismes préalablement identifiés, permet de proposer un modèle physique local de la dégradation photo-radio-induite. La confrontation des simulations issues de ce modèle à une large variété d’observations originales faites « en ligne » conduit à sa validation. Il est ainsi démontré que, pour des débits de dose inférieurs à une valeur critique, la dégradation des FDY pompées et irradiées ne peut excéder leur niveau de photo-noircissementThis thesis deals with the degradation induced by the pump (photodarkening, PN) and ionizing radiations (radiodarkening, RN) in ytterbium-doped optical fiber (YDF) used in harsh environments. Through original experimental characterizations and modeling, it analyses the interplay between PN and RN and reveals important and novel properties of the radiation resistance of pumped YDF. The first part investigates induced defects (color centers) together with their creation/recovery mechanisms. It used a set of post-irradiation characterizations (ESR, RIA, TSL) conducted on preform samples and benefited from their original correlation (thermal recovery protocols coupling TSL and RIA). A systematic study as a function of composition reveals the influence of co-dopants (Al, Ce) on the trapping of carrier freed during ionization processes. The second part examines the darkening build-up under the simultaneous action of the pump and an ionizing irradiation. By using a measurement bench that allowed us to follow the real-time “on line” degradation of fiber samples, we showed that photo- and radio-darkening both arise from the same color centers that can be bleached by the pump. On the basis of this finding and of the preceding identified mechanisms, we propose a local physical model of the photo-radio-induced darkening. The latter is thoroughly validated by further successful comparisons of simulated degradation with a wide variety of “on line” original observations. Then, we notably demonstrate that for dose rates lying below a critical value (explicited by our theory), the degradation of pumped and irradiated YDF never exceeds the photo-darkening level
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Bernal, Olivier. « Conception de Convertisseurs Analogique-Numérique en technologie CMOS basse tension pour chaînes Vidéo CCD Spatiales ». Phd thesis, Toulouse, INPT, 2006. http://oatao.univ-toulouse.fr/7495/1/bernal.pdf.
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Dans le cadre des Instruments d'Observation de la Terre, les technologies microélectroniques sur lesquelles sont basés les systèmes spatiaux embarqués, ont tendance à être de moins en moins basées sur les technologies dites durcies aux radiations au profit de technologies CMOS sub-microniques basse-tension dédiées principalement aux circuits numériques. Aussi, dans un premier temps, des méthodes de durcissement aux radiations présentes dans l'espace ont dû être analysées tant au niveau système qu'au niveau circuit et layout pour améliorer la fiabilité des Convertisseurs Analogique-Numérique (CAN) utilisés dans les chaînes Video CCD. Pour atteindre les performances des futurs imageurs CCD (12 bits à 20 Méchantillons/s), les CAN à architecture pipeline apparaissent comme les plus adaptés. Pour anticiper l'évolution des technologies vers les très basses tensions, les méthodes de conception en courant et en tension ont toutes deux été analysées. Dans ce cadre, l'approche originale en courant a aussi été abordée de par ses propriétés d'auto-calibrage (température, vieillissement). Afin de démontrer la faisabilité de CAN de haute résolution en courant, une mémoire de courant, cellule fondamentale d'un CAN en courant, a été implémentée en technologie CMOS 0.35μm. Le prototype de cette mémoire atteint une résolution supérieure à 13bits à 10Méchantillons/s. Toutefois, les performances en bruit de cette mémoire de courant (¼ 65dB) ne satisfont pas les critères en bruit d'un CAN 12bits. Aussi, une analyse comparative en bruit entre les circuits à capacités commutées en tension et à courants commutés a été effectuée afin de caractériser chacune des approches en bruit et de déterminer l'approche la moins pénalisante. Elle a permis de mettre en évidence un gain de 17dB environ des structures en tension sur celles en courant. C'est pourquoi, une approche en tension dont une méthode de conception optimisée a été développée, apparaît comme nécessaire pour les premiers étages de haute résolution au moins. Contrairement à l'approche en courant qui ne requiert pas de commutateurs analogiques performants et qui par là-même est plus adaptée au contexte spatial, l'approche en tension nécessite des commutateurs fonctionnant sur une large plage de tension. En général, les méthodes de conception basse-tension reposent sur une architecture dite “bootstrappée” pour améliorer leurs caractéristiques. Toutefois, non applicables directement de par les contraintes de l'environnement spatial, une autre architecture basée sur des transistors PMOS a été proposée. Enfin, pour pouvoir relaxer les contraintes sur la conception des circuits analogiques, une nouvelle méthode de calibrage et de correction numérique adaptable à la fois aux CAN en tension et en courant est proposée. Elle permet de corriger les erreurs de gain, d'offsets, et des niveaux de référence utilisés. Elle améliore aussi la linéarité du convertisseur, sa précision absolue, sa consommation et sa robustesse vis-à-vis des radiations. Pour le cas des structures en courant, la méthode proposée permet de doubler la vitesse d'échantillonnage du CAN.
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Belloir, Jean-Marc. « Spectroscopie du courant d’obscurité induit par les effets de déplacement atomique des radiations spatiales et nucléaires dans les capteurs d’images CMOS à photodiode pincée ». Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0029/document.
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Les imageurs CMOS représentent un outil d’avenir pour de nombreuses applications scientifiques de haut vol, tellesque l’observation spatiale ou les expériences nucléaires. En effet, ces imageurs ont vu leurs performancesdémultipliées ces dernières années grâce aux avancées incessantes de la microélectronique, et présentent aussi desavantages indéniables qui les destinent à remplacer les CCDs dans les futurs instruments spatiaux. Toutefois, enenvironnement spatial ou nucléaire, ces imageurs doivent faire face aux attaques répétées de particules pouvantrapidement dégrader leurs performances électro-optiques. En particulier, les protons, électrons et ions présents dansl’espace ou les neutrons de fusion nucléaire peuvent déplacer des atomes de silicium dans le volume du pixel et enrompre la structure cristalline. Ces effets de déplacement peuvent former des défauts stables introduisant des étatsd’énergie dans la bande interdite du silicium, et ainsi conduire à la génération thermique de paires électron-trou. Parconséquent, ces radiations non-ionisantes produisent une augmentation permanente du courant d’obscurité despixels de l’imageur et donc à une diminution de leur sensibilité et de leur dynamique. L’objectif des présents travauxest d’étendre la compréhension des effets de déplacement sur l’augmentation du courant d’obscurité dans lesimageurs CMOS. En particulier, ces travaux se concentrent sur l’étude de la forme de la distribution de courantd’obscurité en fonction du type, de l’énergie et du nombre de particules ayant traversé l’imageur, mais aussi enfonction des caractéristiques de l’imageur. Ces nombreux résultats permettent de valider physiquement etexpérimentalement un modèle empirique de prédiction de la distribution du courant d’obscurité pour une utilisationdans les domaines spatial et nucléaire. Une autre partie majeure de ces travaux consiste à utiliser pour la première foisla technique de spectroscopie de courant d’obscurité pour détecter et caractériser individuellement les défautsgénérés par les radiations non-ionisantes dans les imageurs CMOS. De nombreux types de défauts sont détectés etdeux sont identifiés, prouvant l’applicabilité de cette technique pour étudier la nature des défauts cristallins généréspar les effets de déplacement dans le silicium. Ces travaux avancent la compréhension des défauts responsables del’augmentation du courant d’obscurité en environnement radiatif, et ouvrent la voie au développement de modèles deprédiction plus précis, voire de techniques permettant d’éviter la formation de ces défauts ou de les faire disparaîtreCMOS image sensors are envisioned for an increasing number of high-end scientific imaging applications such asspace imaging or nuclear experiments. Indeed, the performance of high-end CMOS image sensors has dramaticallyincreased in the past years thanks to the unceasing improvements of microelectronics, and these image sensors havesubstantial advantages over CCDs which make them great candidates to replace CCDs in future space missions.However, in space and nuclear environments, CMOS image sensors must face harsh radiation which can rapidlydegrade their electro-optical performances. In particular, the protons, electrons and ions travelling in space or thefusion neutrons from nuclear experiments can displace silicon atoms in the pixels and break the crystalline structure.These displacement damage effects lead to the formation of stable defects and to the introduction of states in theforbidden bandgap of silicon, which can allow the thermal generation of electron-hole pairs. Consequently, nonionizingradiation leads to a permanent increase of the dark current of the pixels and thus a decrease of the imagesensor sensibility and dynamic range. The aim of the present work is to extend the understanding of the effect ofdisplacement damage on the dark current increase of CMOS image sensors. In particular, this work focuses on theshape of the dark current distribution depending on the particle type, energy and fluence but also on the imagesensor physical parameters. Thanks to the many conditions tested, an empirical model for the prediction of the darkcurrent distribution induced by displacement damage in nuclear or space environments is experimentally validatedand physically justified. Another central part of this work consists in using the dark current spectroscopy techniquefor the first time on irradiated CMOS image sensors to detect and characterize radiation-induced silicon bulk defects.Many types of defects are detected and two of them are identified, proving the applicability of this technique to studythe nature of silicon bulk defects using image sensors. In summary, this work advances the understanding of thenature of the radiation-induced defects responsible for the dark current increase in space or nuclear environments. Italso leads the way to the design of more advanced dark current prediction models, or to the development ofmitigation strategies in order to prevent the formation of the responsible defects or to allow their removal
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Jouni, Ali. « Space radiation effects on CMOS single photon avalanche diodes (SPADs) ». Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0012.
Texte intégralRésumé :
Le sujet de cette thèse traite des effets des radiations spatiales sur des détecteurs CMOS à avalanches, et particulièrement sur les dispositifs SPADs (pour Single Photon Avalanche Diode en anglais, ou photodiode à avalanche à photon unique). Ces photodiodes présentent un gain interne presque infini et sont donc sensibles à des très faibles conditions de lumières. Ainsi, avec en plus une excellente résolution temporelle, ces capteurs peuvent être très intéressant pour des applications spatiales nécessitant des mesures de temps de vols, comme la topographie d’objets célestes ou les Rendez-vous spatiaux. Cependant, l’espace est un environnement hostile du fait des radiations provenant du Soleil, des particules piégées dans la magnétosphère terrestre ainsi qu’au-delà du système solaire. De ce fait, dans le cadre de ces travaux de thèse, un modèle est mis en place pour prédire la dégradation du courant d’obscurité des SPADs, le Dark Count Rate (DCR), après des irradiations aux protons. Expérimentalement, deux technologies de matrices de SPADs sont irradiées avec des protons, des rayons X et des rayons γ. De ce fait, les effets ionisants et non-ionisants sont investigués pour ces capteurs à avalanches, et des différences en comparaison avec les pixelsdes capteurs d’images standard sont soulignées. Ensuite, les caractéristiques des défauts induits par la création d’états d’interface entre les oxides et le silicium et les dommages de déplacement atomique dans le substrat sont examinées, avec notamment la présence de comportement RTS (Random Telegraph Signal). Enfin, l’identification de la nature de ces défauts est réalisée par l’intermédiaire de recuits isochrones après l’expositions des matrices de SPADs aux trois différentes radiations mentionnées au-dessusThe subject of this thesis deals with the effects of space radiation on CMOS avalanche detectors, particularly on Single Photon Avalanche Diodes (SPADs). These photodiodes exhibit nearly infinite internal gain and are therefore sensitive to very low light conditions. Thus, with excellent temporal resolution, these sensors can be very interesting for space applications requiring time-of-flight measurements, such as the topography of celestial objects or space Rendezvous. However, space is a hostile environment due to radiation from the Sun, particles trapped in the Earth’s magnetosphere, and beyond the solar system. Consequently, within the framework of this thesis work, a model is established to predict thedegradation of the dark current of SPADs, the Dark Count Rate (DCR), after proton irradiations. Experimentally, two SPAD array technologies are irradiated with protons, X-rays, and γ rays. Hence, ionizing and non-ionizing effects are investigated for these avalanche sensors, and differences compared to pixels of standard image sensors are highlighted. Subsequently, the characteristics of defects induced by the creation of interface traps between oxides and silicon and atomic displacement damage in the substrate are examined, including the presence of Random Telegraph Signal (RTS) behaviors. Finally, the nature of these defects is identified through isochronal annealing after irradiations of the SPAD arrays using the three different radiation types mentioned above
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Ladaci, Ayoub. « Rare earth doped optical fibers and amplifiers for space applications ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES027/document.
Texte intégralRésumé :
Les fibres dopées aux terres rares (REDFs) représentent un composant clef dans la fabrication de sources laser et d’amplificateurs optiques (REDFAs). Leurs hautes performances rendent cette technologie particulièrement attractive pour les applications spatiales en tant que partie active des gyroscopes à fibres optiques, pour le transfert de données et les applications LIDARS. Cependant, la grande sensibilité de ces fibres actives limite l’intégration des REDFAs au sein des missions spatiales. De nombreuses études ont été menées pour dépasser ces limitations et différentes techniques de mitigation ont été identifiées telles que le co-dopage au Cérium ou le chargement en hydrogène de ces fibres optiques. Toutes ces solutions interviennent au niveau du composant sensible et sont classées parmi les stratégies de durcissement par composant permettant la fabrication de fibres dopées aux terres rares résistantes aux radiations adaptées aux besoins des missions spatiales actuelles associées à de faibles doses d’irradiation. Cependant, l’avènement de nouveaux programmes, de nouvelles missions invitent à considérer des doses d’irradiation plus importantes, nécessitant des REDFs et des RDFAs encore plus tolérants aux radiations. A cette fin, une optimisation de l’amplificateur optique au niveau système est étudiée dans le cadre de ce doctorat en exploitant une approche couplant simulation et expériences dont les avancées pourront venir en appui des techniques de durcissement plus conventionnelles. Après la présentation du contexte, des objectifs de ce travail (Chapitre I), les mécanismes fondamentaux de l’amplification et des effets des radiations sont brièvement décrits dans le Chapitre II. Les outils de simulation basés sur l’enrichissement d’un code à l’état de l’art et ses nouvelles fonctionnalités, décrites au Chapitre III, permettent non seulement l’évaluation des performances optiques du REDFA mais aussi de prédire leurs évolutions sous irradiation. De nombreuses études expérimentales ont été réalisées sur différents REDFAs développés durant la thèse et présentés dans le chapitre IV, leurs résultats comparés à ceux issus de la simulation afin de valider nos outils de simulation. Une fois validé, le code a été utilisé pour montrer comment l’optimisation de l’architecture du REDFA permet de mitiger les effets des radiations sur ses performances (Chapitre V). Finalement, le Chapitre VI présente l’étude de l’implémentation dans le code de nouveaux effets, tels que les effets thermiques, le multiplexage du signal d’entrée à travers un couplage théorie/expérienceRare earth doped fibers (REDFs) are a key component in optical laser sources and amplifiers (REDFAs). Their high performances render them very attractive for space applications as the active part of gyroscopes, high data transfer links and LIDARs. However, the high sensitivity of these active fibers to space radiations limits the REDFA integration in actual and future missions. To overcome these issues various studies were carried out and some mitigation techniques were identified such as the Cerium co-doping or the hydrogen loading of the REDFs. All these solutions occur at the component level and are classified as a hardening by component strategy allowing the manufacturing of radiation hardened REDFAs with adapted performances for low doses space mission. However, with the new space research programs, more challenging space missions are targeted with higher radiations doses requiring even more tolerant REDFs and REDFAs. To this aim, an optimization of the REDFA at the system level is investigated in this PhD thesis exploiting an approach coupling simulations and experiments offering the opportunity to benefit from the outputs of this hardening by system strategy in addition to other state-of-the-art approaches. After presenting the context, objectives of this work, the basic mechanisms about amplification and radiation effects as well as the architectures of REDFAs are described in chapters I and II. After that, we update a state of art REDFAs simulation code described in Chapter III, to consider not only the REDFA optical performances but also their evolutions when exposed to radiations. Several experiments on dedicated home-made REDFA have been performed using accelerated irradiation tests (Chapter IV) and the comparison between these data and those obtained through the new code validated the simulation tools. Thereafter, we exploit the validated code to highlight how the optimization of the REDFA architecture can participate to the mitigation of the radiation effects on the amplifier performances (Chapter V). Finally, in chapter VI the implementation in the code of several other effects, such as thermal effects, input signal multiplexing was investigated both from experimental and calculation point of views
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Park, Samuel. « Radiation transport in multiphase and spatially random media ». Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45051.
Texte intégralRésumé :
An important class of problems within radiation (e.g. neutrons, photons) transport are those in which the radiation migrates through a medium which has a random or stochastic composition. The uncertain medium composition introduces an uncertainty in the radiation angular/scalar flux, current, reaction rates and other quantities of interest. Stochastic media play an important role within radiation transport and have numerous applications such as radiation shielding, nuclear criticality assessment, as well as radiative transfer in clouds, stellar atmospheres and plasma physics. Stochastic radiation transport problems reduce to treating the adsorption, scatter and other macroscopic cross-section data as spatially correlated random fields. Several methods for the treatment of these uncertain-ties have been proposed however they are limited in their scope and computational efficiency. Multiphase and spatially random media are often characterised by non-Gaussian random fields which are much more challenging to model than Gaussian random fields. This thesis aims to investigate, develop and implement mathematically rigorous computational algorithms that are more efficient than the current methods for solving radiation transport with multiphase and spatially random media. In particular this thesis applies iso-probabilistic (e.g. Nataf) transforms to transform Gaussian random fields into non-Gaussian random fields. This approach enables the use of optimal spectral stochastic representations, such as the Karhunen-Loève and generalized polynomial chaos methods, to be used to simulate non-Gaussian random fields. This thesis also describes the verification of these iso-probabilistic spectral stochastic projection methods against standard radiation transport in random media benchmarks, such as the widely used Adams-Levermore-Pomraning benchmark. This thesis is the first time the general Nataf method has been applied to model radiation transport through multiphase and spatially random media.
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Al, Youssef Ahmad. « Étude par modélisation des événements singuliers (SET/SEU/SEL) induits par l’environnement radiatif dans les composants électroniques ». Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0021/document.
Texte intégralRésumé :
L’environnement radiatif spatial est particulièrement critique pour la fiabilité des circuits intégrés et systèmes électroniques embarqués. Cet environnement chargé en particules énergétiques (proton, électron, ions lourds, etc) peut conduire à des pannes transitoires (SET), ou permanentes (SEU) et dans certains cas destructives (type Latchup, SEL) dans les dispositifs embarqués. L'effet d'une seule particule est identifié comme un événement singulier (SEE). Les contraintes imposées par l'intégration technologique poussent les fabricants micro-électroniques à prendre en considération la vulnérabilité de leurs composants vis-à-vis du Latchup tout en considérant les phénomènes non destructifs tels que la corruption de données (SEU/MBU). Cette thèse est le fruit d'une collaboration entre l'ONERA et Sofradir, fabriquant électronique d'imageurs infrarouge. L'objectif de cette thèse est d'étudier les effets singuliers (SET/SEU/SEL) de la technologie CMOS utilisée par Sofradir dans des conditions de températures cryogéniques, et plus particulièrement l'effet LatchupThe spatial radiative environment is particularly critical for the reliability of integrated circuits and embedded electronic systems. This environment loaded with energetic particles (proton, electron, heavy ions, etc.) can lead to transient (SET), or permanent (SEU) and insome cases destructive failures (Latchup, SEL) in embedded devices. The effect of a single particle is identified as a single event effect(SEE). The constraints imposed by technological integration push microelectronics manufacturers to consider the vulnerability of their components to Latchup while consideringnon-destructive phenomena such as data corruption (SEU/MBU). This thesis is the result ofcollaboration between ONERA and Sofradir, an electronic manufacturer of infrared imagers. The aim of this thesis is to study the singular effects (SET / SEU / SEL) of the CMOS technology used by Sofradir under cryogenic temperature conditions, and more particularly the Latchup effect
Livres sur le sujet "Radiations spatiales"
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Sheng-I, Hsu. Spatial variation of solar radiation in Hong Kong. Hong Kong : Chinese University of Hong Kong, Dept.of Geography, 1986.
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W, Townsend Lawrence, Wilson J. W et United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., dir. Benchmark solutions for the galactic ion transport equations : Energy and spatially dependent problems. [Washington, DC] : National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.
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Center, Goddard Space Flight, dir. Small-scale spatial fluctuations in the soft X-ray background. Greenbelt, Md : National Aeronautics and Space Administration, Goddard Space Flight Center, 2001.
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Kuntz, Kip D. Small-scale spatial fluctuations in the soft X-ray background. Greenbelt, Md : National Aeronautics and Space Administration, Goddard Space Flight Center, 2001.
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Center, Goddard Space Flight, dir. Small-scale spatial fluctuations in the soft X-ray background. Greenbelt, Md : National Aeronautics and Space Administration, Goddard Space Flight Center, 2001.
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Quattrochi, Dale A. Spatial and temporal scaling of thermal infrared remote sensing data. [Washington, D.C : National Aeronautics and Space Administration, 1995.
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National Council on Radiation Protection and Measurements. Radiation protection for space activities : Supplement to previous recommendations. Bethesda, Maryland : National Council on Radiation Protection and Measurements, 2014.
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National Council on Radiation Protection and Measurements. Guidance on radiation received in space activities. Bethesda, Md : NCRP, 1989.
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National Council on Radiation Protection and Measurements. Potential impact of individual genetic susceptibility and previous radiation exposure on radiation risk for astronauts. Bethesda, Md : National Council on Radiation Protection and Measurements, 2011.
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United States. National Aeronautics and Space Administration., dir. Exploration of the solar-stellar connection at high specral resolution with the ultraviolet spectrometer and polarimeter and studies of thermal bifurcation at the ... Boulder, CO : University of Colorado at Boulder, 1987.
Trouver le texte intégralChapitres de livres sur le sujet "Radiations spatiales"
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Weik, Martin H. « spatially coherent radiation ». Dans Computer Science and Communications Dictionary, 1626. Boston, MA : Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_17820.
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Hammer, Annette, et H. G. Beyer. « Solar Radiation solar radiation , Spatial Solar Radiation spatial variability and Temporal Variability solar radiation temporal variability solar radiation spatial variability ». Dans Encyclopedia of Sustainability Science and Technology, 9744–58. New York, NY : Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-0851-3_449.
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Hammer, Annette, et H. G. Beyer. « Solar Radiation solar radiation , Spatial Solar Radiation spatial variability and Temporal Variability solar radiation temporal variability solar radiation spatial variability ». Dans Solar Energy, 634–48. New York, NY : Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-5806-7_449.
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Rosanov, Nikolay N. « Nonlinear Radiation Reflection ». Dans Spatial Hysteresis and Optical Patterns, 177–205. Berlin, Heidelberg : Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-04792-7_5.
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Evans, Charles R., Larry L. Smarr et James R. Wilson. « Numerical Relativistic Gravitational Collapse with Spatial Time Slices ». Dans Astrophysical Radiation Hydrodynamics, 491–529. Dordrecht : Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4754-2_15.
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Zhian, Sun, et Weng Duming. « A Climatological Calculation Method for Effective Radiation With its Spatial and Temporal Distribution Over China ». Dans Atmospheric Radiation, 145–48. Boston, MA : American Meteorological Society, 1987. http://dx.doi.org/10.1007/978-1-935704-18-8_24.
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Guodong, Gao, et Lu Yurong. « Calculation and Spatial and Temporal Distributions of the Components of the Radiation Balance for China ». Dans Atmospheric Radiation, 189–95. Boston, MA : American Meteorological Society, 1987. http://dx.doi.org/10.1007/978-1-935704-18-8_30.
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Zhibao, Shen, Yang Huayi et Ji Guoliang. « The Characteristics of Temporal and Spatial Variations in the Surface Radiation Balance Over the Qinghai-Xizang Plateau ». Dans Atmospheric Radiation, 52–62. Boston, MA : American Meteorological Society, 1987. http://dx.doi.org/10.1007/978-1-935704-18-8_11.
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Koskinen, Hannu E. J., et Emilia K. J. Kilpua. « Radiation Belts and Their Environment ». Dans Astronomy and Astrophysics Library, 1–25. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-82167-8_1.
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AbstractThe Van Allen radiation belts of high-energy electrons and ions, mostly protons, are embedded in the Earth’s inner magnetosphere where the geomagnetic field is close to that of a magnetic dipole. Understanding of the belts requires a thorough knowledge of the inner magnetosphere and its dynamics, the coupling of the solar wind to the magnetosphere, and wave–particle interactions in different temporal and spatial scales. In this introductory chapter we briefly describe the basic structure of the inner magnetosphere, its different plasma regions and the basics of magnetospheric activity.
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Bowman, Michael K., Alexander G. Maryasov et Yuri D. Tsvetkov. « EPR Measurement of the Spatial Distribution of Radiation Damage ». Dans Applications of EPR in Radiation Research, 581–627. Cham : Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09216-4_16.
Texte intégralActes de conférences sur le sujet "Radiations spatiales"
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Taylor, E. W., A. D. Sanchez, S. P. Chapman, S. A. De Walt, D. M. Craig, M. A. Kelly et M. F. Mitcham. « Responses of a Spatial Light Modulator to Pulsed Electron Irradiations ». Dans Spatial Light Modulators and Applications. Washington, D.C. : Optica Publishing Group, 1995. http://dx.doi.org/10.1364/slma.1995.lthd4.
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The application of photonic technologies in space and enhanced environments has progressed steadily. The first survivable fiber optic point to point links were demonstrated in 19841, paving the way for other proposed experiments including acousto-optic devices2. Radiation hardness studies of integrated3 and coupled wave optic4 devices have been performed. Photonic hardness standards are progressing from the studies of international round robin teams5,6. However, limited data exists on the radiation responses of organic spatial light modulators7 (SLMs) or acousto-optic modulators in radiation environments. This paper partially addresses this issue by examining the radiation response of a SLM.
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Luo, Qingzhou, Yechao Yan et Shuping Yue. « Computation of hillshade values considering diffuse radiation condition ». Dans International Symposium on Spatial Analysis, Spatial-temporal Data Modeling, and Data Mining, sous la direction de Yaolin Liu et Xinming Tang. SPIE, 2009. http://dx.doi.org/10.1117/12.838393.
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Sun, Li-Bo, et J. Fred Holmes. « Measurement of spatially filtered laser radiation in atmospheric turbulence ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.fp8.
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One effect of atmospheric turbulence on laser beam propagation is to randomly spatially modulate the intensity. Consequently, by optically spatially filtering the received intensity, the turbulence-induced spatial modulation can be separated from other effects. In a previous paper, the theory applicable to this problem was developed. This work involves measurement of the on-axis mean, variance, and autocovariance of the intensity for line of sight laser propagation after the received radiation has been high-pass spatially filtered. The experiment was conducted over a flat, featureless 500-m atmospheric propagation path that has nearly uniform turbulence. The experimental results are compared to theory and the usefulness of the technique for sensing the strength of turbulence discussed.
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Parshin, Yury N., et Maxim V. Grachev. « Efficiency of the Angular Coordinate Estimation under the Action of Spatially Correlated Interferences and Mutual Influence of Spatial Channels ». Dans 2019 Radiation and Scattering of Electromagnetic Waves (RSEMW). IEEE, 2019. http://dx.doi.org/10.1109/rsemw.2019.8792801.
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Hoszowska, J. « Spatial Coherence Preservation By Synthetic Single Diamond Crystals ». Dans SYNCHROTRON RADIATION INSTRUMENTATION : Eighth International Conference on Synchrotron Radiation Instrumentation. AIP, 2004. http://dx.doi.org/10.1063/1.1757901.
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Fedotova, Anna, Mohammadreza Younesi, Dennis Arslan, Thomas Pertsch, Isabelle Staude et Frank Setzpfandt. « Second-Harmonic Generation from Metasurfaces with Spatially Engineered Nonlinearity ». Dans CLEO : QELS_Fundamental Science. Washington, D.C. : Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_qels.2022.fth4b.7.
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We demonstrate resonant metasurfaces with spatially engineered nonlinearity based on periodically poled lithium niobate. Such spatial control of the nonlinearity unlocks additional degrees of freedom for controlling the properties of second-harmonic radiation from metasurfaces.
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Wu, Ziling, Iksung Kang, Tao Zhou, Van Coykendall, Baoliang Ge, Mathew J. Cherukara et George Barbastathis. « Photon-starved X-ray Ptychographic Imaging using Spatial Pyramid Atrous Convolution End-to-end Reconstruction (PtychoSPACER) ». Dans Computational Optical Sensing and Imaging. Washington, D.C. : Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cosi.2022.cf1d.6.
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We realize low-dose X-ray ptychography via Spatial Pyramid Atrous Convolution End-to-end Reconstruction (PtychoSPACER), which offers nanometer-scale resolution on the complex index of refraction for spatially extended samples non-destructively and reduces the risk of radiation damage.
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Tang, Mau-Tsu, Yen-Fang Song, Gung-Chian Yin, Fu-Rong Chen, Jian-Hua Chen, Yi-Ming Chen, Keng S. Liang, F. Duewer et Wenbing Yun. « Hard X-ray Microscopy with sub 30 nm Spatial Resolution ». Dans SYNCHROTRON RADIATION INSTRUMENTATION : Ninth International Conference on Synchrotron Radiation Instrumentation. AIP, 2007. http://dx.doi.org/10.1063/1.2436296.
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Lo, Y. C. « Performance Of An Infrared Beamline For High Spatial Resolution FTIR Microscopy ». Dans SYNCHROTRON RADIATION INSTRUMENTATION : Eighth International Conference on Synchrotron Radiation Instrumentation. AIP, 2004. http://dx.doi.org/10.1063/1.1757838.
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James, Daniel F. V. « Quantum-optical analysis of Wolf’s spectral shifts ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.fc6.
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Not long ago Wolf discovered a modification of the spectrum of radiation due to the spatial coherence of the source.1 His analysis used a model correlation function that demonstrated the effect, without discussing any physical mechanism by which the correlations may arise. This paper presents an analysis of one such physical mechanism, namely, the radiation reaction. Following earlier work by Varada and Agarwal,2 an explicit calculation, performed in the harmonic oscillator approximation, for two radiating atoms in equilibrium with a thermal field reveals a relationship between this effect and the well-known shift of atomic oscillator frequencies due to Lamb.
Rapports d'organisations sur le sujet "Radiations spatiales"
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Morkun, Volodymyr, Natalia Morkun, Andrii Pikilnyak, Serhii Semerikov, Oleksandra Serdiuk et Irina Gaponenko. The Cyber-Physical System for Increasing the Efficiency of the Iron Ore Desliming Process. CEUR Workshop Proceedings, avril 2021. http://dx.doi.org/10.31812/123456789/4373.
Texte intégralRésumé :
It is proposed to carry out the spatial effect of high-energy ultrasound dynamic effects with controlled characteristics on the solid phase particles of the ore pulp in the deslimer input product to increase the efficiency of thickening and desliming processes of iron ore beneficiation products. The above allows predicting the characteristics of particle gravitational sedimentation based on an assessment of the spatial dynamics of pulp solid- phase particles under the controlled action of high-energy ultrasound and fuzzy logical inference. The object of study is the assessment of the characteristics and the process of control the operations of thickening and deslaming of iron ore beneficiation products in the conditions of the technological line of the ore beneficiation plant. The subject of study is a cyber-physical system based on the use of high-energy ultrasound radiation pressure effects on iron-containing beneficiation products in the technological processes of thickening and desliming. The working hypothesis of the project is that there is a relationship between the physical-mechanical and chemical-mineralogical characteristics of the iron ore pulp solid- phase particles and their behavior in technological flows under the influence of controlled ultrasonic radiation, based on which the imitation modeling of the gravitational sedimentation process of the iron ore pulp solid-phase particles can be performed directly in the technological process. Also, the optimal control actions concerning the processes of thickening and desliming can be determined.
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Jing, Tao. High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator. Office of Scientific and Technical Information (OSTI), mai 1995. http://dx.doi.org/10.2172/95260.
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Clausen, Jay, Susan Frankenstein, Jason Dorvee, Austin Workman, Blaine Morriss, Keran Claffey, Terrance Sobecki et al. Spatial and temporal variance of soil and meteorological properties affecting sensor performance—Phase 2. Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/41780.
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An approach to increasing sensor performance and detection reliability for buried objects is to better understand which physical processes are dominant under certain environmental conditions. The present effort (Phase 2) builds on our previously published prior effort (Phase 1), which examined methods of determining the probability of detection and false alarm rates using thermal infrared for buried-object detection. The study utilized a 3.05 × 3.05 m test plot in Hanover, New Hampshire. Unlike Phase 1, the current effort involved removing the soil from the test plot area, homogenizing the material, then reapplying it into eight discrete layers along with buried sensors and objects representing targets of inter-est. Each layer was compacted to a uniform density consistent with the background undisturbed density. Homogenization greatly reduced the microscale soil temperature variability, simplifying data analysis. The Phase 2 study spanned May–November 2018. Simultaneous measurements of soil temperature and moisture (as well as air temperature and humidity, cloud cover, and incoming solar radiation) were obtained daily and recorded at 15-minute intervals and coupled with thermal infrared and electro-optical image collection at 5-minute intervals.
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Lent, E. M., et W. C. Dickinson. Spatial distribution of radiation from the Beam Line VIII-W 15-period wiggler. Office of Scientific and Technical Information (OSTI), mai 1985. http://dx.doi.org/10.2172/5526417.
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Clausen, Jay, Michael Musty, Anna Wagner, Susan Frankenstein et Jason Dorvee. Modeling of a multi-month thermal IR study. Engineer Research and Development Center (U.S.), juillet 2021. http://dx.doi.org/10.21079/11681/41060.
Texte intégralRésumé :
Inconsistent and unacceptable probability of detection (PD) and false alarm rates (FAR) due to varying environmental conditions hamper buried object detection. A 4-month study evaluated the environmental parameters impacting standoff thermal infra-red(IR) detection of buried objects. Field observations were integrated into a model depicting the temporal and spatial thermal changes through a 1-week period utilizing a 15-minute time-step interval. The model illustrates the surface thermal observations obtained with a thermal IR camera contemporaneously with a 3-d presentation of subsurface soil temperatures obtained with 156 buried thermocouples. Precipitation events and subsequent soil moisture responses synchronized to the temperature data are also included in the model simulation. The simulation shows the temperature response of buried objects due to changes in incoming solar radiation, air/surface soil temperature changes, latent heat exchange between the objects and surrounding soil, and impacts due to precipitation/changes in soil moisture. Differences are noted between the thermal response of plastic and metal objects as well as depth of burial below the ground surface. Nearly identical environmental conditions on different days did not always elicit the same spatial thermal response.
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Fassnacht, Steven, Kazuyoshi Suzuki, Jessica Sanow, Graham Sexstone, Anna Pfohl, Molly Tedesche, Bradley Simms et Eric Thomas. Snow surface roughness across spatio-temporal scales. Engineer Research and Development Center (U.S.), septembre 2024. http://dx.doi.org/10.21079/11681/49199.
Texte intégralRésumé :
The snow surface is at the interface between the atmosphere and Earth. The surface of the snowpack changes due to its interaction with precipitation, wind, humidity, short- and long-wave radiation, underlying terrain characteristics, and land cover. These connections create a dynamic snow surface that impacts the energy and mass balance of the snowpack, blowing snow potential, and other snowpack processes. Despite this, the snow surface is generally considered a constant parameter in many Earth system models. Data from the National Aeronautics and Space Administration (NASA) Cold Land Processes Experiment (CLPX) collected in 2002 and 2003 across northern Colorado were used to investigate the spatial and temporal variability of snow surface roughness. The random roughness (RR) and fractal dimension (D) metrics used in this investigation are well correlated. However, roughness is not correlated across scales, computed here from snow roughness boards at a millimeter resolution and airborne lidar at a meter resolution. Process scale differences were found based on land cover at each of the two measurement scales, as appraised through measurements in the forest and alpine.
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Ruosteenoja, Kimmo. Applicability of CMIP6 models for building climate projections for northern Europe. Finnish Meteorological Institute, septembre 2021. http://dx.doi.org/10.35614/isbn.9789523361416.
Texte intégralRésumé :
In this report, we have evaluated the performance of nearly 40 global climate models (GCMs) participating in Phase 6 of the Coupled Model Intercomparison Project (CMIP6). The focus is on the northern European area, but the ability to simulate southern European and global climate is discussed as well. Model evaluation was started with a technical control; completely unrealistic values in the GCM output files were identified by seeking the absolute minimum and maximum values. In this stage, one GCM was rejected totally, and furthermore individual output files from two other GCMs. In evaluating the remaining GCMs, the primary tool was the Model Climate Performance Index (MCPI) that combines RMS errors calculated for the different climate variables into one index. The index takes into account both the seasonal and spatial variations in climatological means. Here, MCPI was calculated for the period 1981—2010 by comparing GCM output with the ERA-Interim reanalyses. Climate variables explored in the evaluation were the surface air temperature, precipitation, sea level air pressure and incoming solar radiation at the surface. Besides MCPI, we studied RMS errors in the seasonal course of the spatial means by examining each climate variable separately. Furthermore, the evaluation procedure considered model performance in simulating past trends in the global-mean temperature, the compatibility of future responses to different greenhouse-gas scenarios and the number of available scenario runs. Daily minimum and maximum temperatures were likewise explored in a qualitative sense, but owing to the non-existence of data from multiple GCMs, these variables were not incorporated in the quantitative validation. Four of the 37 GCMs that had passed the initial technical check were regarded as wholly unusable for scenario calculations: in two GCMs the responses to the different greenhouse gas scenarios were contradictory and in two other GCMs data were missing from one of the four key climate variables. Moreover, to reduce inter-GCM dependencies, no more than two variants of any individual GCM were included; this led to an abandonment of one GCM. The remaining 32 GCMs were divided into three quality classes according to the assessed performance. The users of model data can utilize this grading to select a subset of GCMs to be used in elaborating climate projections for Finland or adjacent areas. Annual-mean temperature and precipitation projections for Finland proved to be nearly identical regardless of whether they were derived from the entire ensemble or by ignoring models that had obtained the lowest scores. Solar radiation projections were somewhat more sensitive.
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Peralta, Airy, et Chris Ray. Lagomorph ladders : Assessing a multi-host community and potential for spillover of rabbit hemorrhagic disease at Great Sand Dunes National Park and Preserve. National Park Service, 2024. http://dx.doi.org/10.36967/2303667.
Texte intégralRésumé :
Rabbit hemorrhagic disease virus type 2 (RHDV2) has caused dramatic declines in rabbits and hares on several continents, with cascading effects on local ecology. Recent mortalities have been reported for several rabbit and hare species in the United States, suggesting broad susceptibility of lagomorphs. If this susceptibility extends to the American pika (Ochotona princeps), the most cold-adapted lagomorph, it could compound climate-mediated threats to this species. Due to climate change, American pikas are predicted to experience significant upslope range retraction during this century. Using an analogy borrowed from wildfire scenarios, other lagomorph species occurring at lower and mid-elevations could act as ?ladder fuels? to wick RHDV2 into high-elevation pika populations. To address this concern, we investigated spatial patterns of habitat use by pikas and other lagomorphs in Great Sand Dunes National Park and Preserve (GRSA), which borders several counties that have reported RHDV2. In 2022, we surveyed 115 plots from a spatially balanced sample of pika habitats in the park, including 48 legacy plots from a pika survey conducted in 2010-2012. Pika detections at the plot level were paired with topographic and environmental indices to estimate minimum habitat occupancy and determine its covariates. Leporid (rabbit and hare) detections at these same plots were used to model presence using similar covariates and correcting for imperfect detection. Our best-supported models of pika and leporid presence were then used to estimate the probability of contact between these taxa within the park. Our mean estimate of pika habitat occupancy was at least 95% during 2022 in GRSA, slightly higher than in 2010-2012, and effects of elevation and precipitation on pika occupancy were as expected from the previous study. Leporid presence at these same plots was 48% after correcting for imperfect detection. The best model of leporid presence supported a negative effect of elevation, in agreement with other studies of these taxa. The best pika and leporid models also included a positive effect of incoming solar radiation. Finally, we used our best models of pika habitat occupancy and leporid presence within the park to map the potential for areas of contact and RHDV2 transmission between these taxa. Our results indicate some potential for contact within subalpine forests, Specifically in the northern half of the park near the lower reach of the Sand Creek Trail and in the far south just north of California Peak.
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Fitzpatrick, Patrick, et Yee Lau. CONCORDE Meteorological Analysis (CMA) - Data Guide. The University of Southern Mississippi, 2023. http://dx.doi.org/10.18785/sose.003.
Texte intégralRésumé :
CONCORDE is the CONsortium for oil spill exposure pathways in COastal River-Dominated Ecosystems (CONCORDE), and is an interdisciplinary research program funded by the Gulf of Mexico Research Initiative (GoMRI) to conduct scientific studies of the impacts of oil, dispersed oil and dispersant on the Gulf’s ecosystem (Greer et al. 2018). A CONCORDE goal is to implement a synthesis model containing circulation and biogeochemistry components of the Northern Gulf of Mexico shelf system which can ultimately aid in prediction of oil spill transport and impacts. The CONCORDE Meteorological Analysis (CMA) is an hourly gridded NetCDF dataset which provides atmospheric forcing for the synthesis model. CMA includes a variety of parameters from multiple sources. The Real-Time Mesoscale Analysis (RTMA; De Pondeca et al. 2011) provides the surface momentum and the thermodynamic atmospheric data. The radiation parameters and total cloud cover percentage are from the North American Mesoscale (NAM) Forecast System fields. The hourly precipitation is extracted from the Next Generation Weather Radar (NEXRAD) Level-III. Gridded sea surface temperature fields (SST) are computed daily using a 10-day running mean of the Advanced Very High-Resolution Radiometer (AVHRR) SST product. The Coupled Ocean-Atmosphere Response Experiment flux (COARE) algorithm calculates sensible heat flux and surface momentum stresses (Fairall et al. 2003). CMA’s spatial domain’s lowest west grid point is at 90.13°W, 29°N, and the highest east grid point is at 87.05°W, 30.94°N. The grid spacing is 0.01 degree, and the grid dimension is 309 by 195.
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Lassen Volcanic National Park Cascades frog and eDNA inventory final report. National Park Service, 2023. http://dx.doi.org/10.36967/2300696.
Texte intégralRésumé :
The Cascades frog (Rana cascadae) is one of two frog species known to occur historically in Lassen Volcanic National Park (LAVO) in Northern California. However, no Cascades frogs have been documented in LAVO for several decades, despite repeated surveys. Threats to the species include natural predators, introduction of fish into historically fishless habitats, diseases like fungal pathogens, airborne drift of pesticides from nearby agricultural areas, ultraviolet (UV-B) radiation, wildfires, and habitat loss from human development and climate change. Objectives of this project were to conduct surveys for Cascades frogs at LAVO using both visual encounter surveys (VES) and environmental DNA (eDNA) surveys at locations with potential for reintroduction, conduct VES and eDNA surveys for potential predators (rainbow trout, brook trout, brown trout, and leeches) to determine locations unsuitable for reintroduction, and to develop a suitability model to assess reintroduction potential within LAVO for Cascades frogs. Fifty locations around LAVO were sampled during this study. Suitability for Cascades frogs was ranked according to suitable vegetation availability, elevation, climatic factors, and perennial water availability. Projected climate data was used to derive future climate suitability for Cascades frogs within and around LAVO. No Cascades frog egg masses, larvae, or adults were detected during VES or eDNA sampling within LAVO in 2021. Pacific tree frogs were observed at 18 sites, indicating suitable larval frog habitat at these sites. At 12 of these 18 sites, trout were not detected with either VES or eDNA sampling and leeches were only detected in two locations. The eDNA survey did not appear to be an effective way to detect leeches, but this method was effective for trout species and Cascades frogs. Climate, vegetation, elevation, and perennial water availability were summarized and combined to identify suitable locations within and around LAVO. Climate data for known locations of Cascades frogs in California were used to define a range of suitable climate conditions for the species and then extrapolated across the Cascade frog?s range in California. Within LAVO, occurrence data were not available and, thus, known habitat preferences were combined with spatial data to establish the location and density of suitable vegetation communities and the availability of perennial water. The most suitable areas within the park were identified to occur along the outer boundary and eastern side of the Park. These locations had optimal climate conditions, suitable vegetation communities and available perennial water sources. Many of the areas with high suitability in LAVO were impacted in recent burns (2021), which will reduce their current overall suitability until the vegetation recovers. Projected climate scenarios suggest that, in general, areas surrounding LAVO will decline in temperature suitability while areas within LAVO will increase. Using all available information, sites (based on sub-watersheds) were determined to be of high, medium, or low reintroduction potential. Sites of high reproduction potential included the Cluster Lakes area; Feather Lake and nearby pond; Horseshoe Lake, Snag Lake and Grassy Creek, and vernal pool near Snag Lake trail; and Willow Lake. All the sites with high reproduction potential will require active management to prepare them for Cascades frogs and to maintain them as suitable habitat into the future.