Дисертації з теми "Radiating surface"
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1
Spadanuda, Enrica. "Surface cloud radiative forcing from broadband radiation measurements on the Antarctic plateau." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10201/.
Повний текст джерелаАнотація:
Surface based measurements systems play a key role in defining the ground truth for climate modeling and satellite product validation. The Italian-French station of Concordia is operative year round since 2005 at Dome C (75°S, 123°E, 3230 m) on the East Antarctic Plateau. A Baseline Surface Radiation Network (BSRN) site was deployed and became operational since January 2006 to measure downwelling components of the radiation budget, and successively was expanded in April 2007 to measure upwelling radiation. Hence, almost a decade of measurement is now available and suitable to define a statistically significant climatology for the radiation budget of Concordia including eventual trends, by specifically assessing the effects of clouds and water vapor on SW and LW net radiation. A well known and robust clear sky-id algorithm (Long and Ackerman, 2000) has been operationally applied on downwelling SW components to identify cloud free events and to fit a parametric equation to determine clear-sky reference along the Antarctic daylight periods (September to April). A new model for surface broadband albedo has been developed in order to better describe the features the area. Then, a novel clear-sky LW parametrization, based on a-priori assumption about inversion layer structure, combined with daily and annual oscillations of the surface temperature, have been adopted and validated. The longwave based method is successively exploited to extend cloud radiative forcing studies to nighttime period (winter). Results indicated inter-annual and intra-annual warming behaviour, i.e. 13.70 W/m2 on the average, specifically approaching neutral effect in summer, when SW CRF compensates LW CRF, and warming along the rest of the year due prevalentely to CRF induced on the LW component.
2
Abidin, Z. Z. "Design, modelling and implementation of antennas using electromagnetic bandgap material and defected ground planes. Surface Meshing Analysis and Genetic Algorithm Optimisation on EBG and Defected Ground Structures for Reducing the Mutual Coupling between Radiating Elements of Antenna Array and MIMO Systems." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5385.
Повний текст джерелаАнотація:
The main objective of this research is to design, model and implement several antenna
geometries using electromagnetic band gap (EBG) material and a defected ground
plane. Several antenna applications are addressed with the aim of improving
performance, particularly the mutual coupling between the elements.
The EBG structures have the unique capability to prevent or assist the propagation of
electromagnetic waves in a specific band of frequencies, and have been incorporated
here in antenna structures to improve patterns and reduce mutual coupling in multielement
arrays. A neutralization technique and defected ground plane structures have
also been investigated as alternative approaches, and may be more practical in real
applications.
A new Uni-planar Compact EBG (UC-EBG) formed from a compact unit cell was
presented, giving a stop band in the 2.4 GHz WLAN range. Dual band forms of the
neutralization and defected ground plane techniques have also been developed and
measured. The recorded results for all antenna configurations show good improvement
in terms of the mutual coupling effect.
The MIMO antenna performance with EBG, neutralization and defected ground of
several wireless communication applications were analysed and evaluated. The
correlation coefficient, total active reflection coefficient (TARC), channel capacity and
capacity loss of the array antenna were computed and the results compared to
measurements with good agreement.
In addition, a computational method combining Genetic Algorithm (GA) with surface
meshing code for the analysis of a 2×2 antenna arrays on EBG was developed. Here the
impedance matrix resulting from the meshing analysis is manipulated by the GA
process in order to find the optimal antenna and EBG operated at 2.4 GHz with the goal
of targeting a specific fitness function. Furthermore, an investigation of GA on 2×2
printed slot on DGS was also done.Ministry of Higher Education Malaysia and Universiti Tun Hussein Onn Malaysia (UTHM)
3
Abidin, Zuhairiah Zainal. "Design, modelling and implementation of antennas using electromagnetic bandgap material and defected ground planes : surface meshing analysis and genetic algorithm optimisation on EBG and defected ground structures for reducing the mutual coupling between radiating elements of antenna array MIMO systems." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5385.
Повний текст джерелаАнотація:
The main objective of this research is to design, model and implement several antenna geometries using electromagnetic band gap (EBG) material and a defected ground plane. Several antenna applications are addressed with the aim of improving performance, particularly the mutual coupling between the elements. The EBG structures have the unique capability to prevent or assist the propagation of electromagnetic waves in a specific band of frequencies, and have been incorporated here in antenna structures to improve patterns and reduce mutual coupling in multielement arrays. A neutralization technique and defected ground plane structures have also been investigated as alternative approaches, and may be more practical in real applications. A new Uni-planar Compact EBG (UC-EBG) formed from a compact unit cell was presented, giving a stop band in the 2.4 GHz WLAN range. Dual band forms of the neutralization and defected ground plane techniques have also been developed and measured. The recorded results for all antenna configurations show good improvement in terms of the mutual coupling effect. The MIMO antenna performance with EBG, neutralization and defected ground of several wireless communication applications were analysed and evaluated. The correlation coefficient, total active reflection coefficient (TARC), channel capacity and capacity loss of the array antenna were computed and the results compared to measurements with good agreement. In addition, a computational method combining Genetic Algorithm (GA) with surface meshing code for the analysis of a 2×2 antenna arrays on EBG was developed. Here the impedance matrix resulting from the meshing analysis is manipulated by the GA process in order to find the optimal antenna and EBG operated at 2.4 GHz with the goal of targeting a specific fitness function. Furthermore, an investigation of GA on 2×2 printed slot on DGS was also done.
4
Руденко, Іван Леонідович. "Планарна електродинамічна акустична система". Master's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/30597.
Повний текст джерелаАнотація:
Проведено огляд історії розвитку виробництва перетворювачів та електродинамічних перетворювачів. Приведено повну класифікацію гучномовців та їх принцип дії.
Здійснили глибокий аналіз конструкції електродинамічних перетворювачів та їх принцип дії. Приведені основні елементи конструктивних рішень.
Виконано моделювання конструктивного рішення планарного електродинамічного перетворювача. Виконано моделювання роботи магнітної та коливальної системи. Приведено графіки основних результатів моделювання та експериментальних вимірювань.
Структура та об’єм роботи: дипломна робота складається з вступу, 3 розділів, висновків, списку використаної літератури. Загальний обсяг дипломної роботи складає (106) сторінок. Робота містить рисунків, (48) таблиць (20) та список використаних джерел із (12) найменувань.A review of the history of the production of converters and electrodynamic transducers was conducted. The full classification of speakers and their principle of action are given. The deep analyzes of the structures of electrodynamic transducers and their principle of action are carried out. The basic elements of constructive decisions are given. The simulation of the constructive decision of a planar electrodynamic converter is executed. The simulation of the work of the magnetic and oscillating system is performed. The graphs of the main results of simulation and experimental measurements are presented. Structure and volume of work: the thesis consists of the introduction, 3 chapters, conclusions, list of used literature. The total volume of the thesis is (106) pages. The work contains drawings, (48) tables (20) and list of sources used from (12) names.
5
Konidaris, Spyridon G. "Electromagnetic scattering from rough surfaces using the On-Surface Radiation Boundary Condition (OSRC) method." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30624.
Повний текст джерелаАнотація:
Approved for public release, distribution unlimitedElectromagnetic scattering from rough surfaces is of prime importance in the engineering field since it affects communications, radar, remote sensing, acoustics, etc. The actual problem of scattering from rough surfaces is complicated and involves three dimensional scattering from either lossy or dielectric, electrically large surface. Integral equations are widely utilized to solve this kind of problem but this solution to the problem is generally computationally intensive. In the On-Surface Radiation Boundary Condition (OSRC) method, a higher order radiation condition is imposed directly on the surface of the scatterer. This reduces the integral equation for the scattered field to a line integral which can be easily evaluated numerically. In this thesis, the OSRC method is used to formulate the problem of scattering from periodic rough, two dimensional surfaces illuminated by a transverse magnetic, plane electromagnetic wave. Three geometric surfaces are considered. A comparison is made between the present formulation, the exact solution, and the physical optics approximation.
6
IRINEU, ROSA M. da S. "Comparação das propriedades das superfícies da poliamida 6.6. tratada por plasma e por radiação ionizante." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9963.
Повний текст джерелаАнотація:
Made available in DSpace on 2014-10-09T12:33:18Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:16Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
7
Chauveheid, Daniel. "Ecoulements multi-matériaux et multi-physiques : solveur volumes finis eulérien co-localisé avec capture d’interfaces, analyse et simulations." Thesis, Cachan, Ecole normale supérieure, 2012. http://www.theses.fr/2012DENS0032/document.
Повний текст джерелаАнотація:
Ce travail de thèse porte sur l'extension et l'analyse d'un solveur volumes finis eulérien, co-localisé avec capture d'interfaces pour la simulation des écoulements multi-matériaux non miscibles. Les extensions proposées s'inscrivent dans la volonté d'élaborer un outil de simulation multi-physiques. Dans le cadre de ce mémoire, le caractère multi-physiques recouvre les champs que nous allons détailler. Nous traitons le cas des écoulements radiatifs modélisés par un système à deux températures qui couple les phénomènes purement hydrodynamiques aux phénomènes radiatifs. Nous proposons un solveur permettant la prise en compte des effets de tension superficielle à l'interface entre deux fluides. Nous développons un solveur implicite permettant la simulation précise d'écoulements faisant intervenir de faibles nombres de Mach par le biais d'une méthode de renormalisation de la diffusion numérique. Enfin, les effets tri-dimensionnels sont considérés ainsi que la possibilité d'étendre le schéma de base aux écoulements à un nombre quelconque de matériaux. A chaque étape, les solveurs développés sont validés sur des cas-testsThis work is devoted to the extension of a eulerian cell-centered finite volume scheme with interfaces capturing for the simulation of multimaterial fluid flows. Our purpose is to develop a simulation tool which could be able to handle multi-physics problems in the following sense. We address the case of radiating flows, modeled by a two temperature system of equations where the hydrodynamics are coupled to radiation transport. We address a numerical scheme for taking surface tension forces into account. An implicit scheme is proposed to handle low Mach number fluid flows by means of a renormalization of the numerical diffusion. Eventually, the scheme is extended to three-dimensional flows and to multimaterial flows, that is with an arbitrary number of materials. At each step, numerical simulations validate our schemes
8
Zygmuntowska, Marta, Thorsten Mauritsen, Johannes Quaas, and Lars Kaleschke. "Arctic clouds and surface radiation." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185357.
Повний текст джерелаАнотація:
Clouds regulate the Earth’s radiation budget, both by reflecting part of the incoming sunlight leading to cooling and by absorbing and emitting infrared radiation which tends to have a warming effect. Globally averaged, at the top of the atmosphere the cloud radiative effect is to cool the climate, while at the Arctic surface, clouds are thought to be warming. Here we compare a passive instrument, the AVHRR-based
retrieval from CM-SAF, with recently launched active instruments
onboard CloudSat and CALIPSO and the widely used ERA-Interim reanalysis. We find that in particular in winter months the three data sets differ significantly. While passive satellite instruments have serious difficulties, detecting only half the cloudiness of the modeled clouds in the reanalysis, the active instruments are in between. In summer, the
two satellite products agree having monthly means of 70–80 percent, but the reanalysis are approximately ten percent higher. The monthly mean long- and shortwave components of the surface cloud radiative effect obtained from the ERAInterim reanalysis are about twice that calculated on the basis of CloudSat’s radar-only retrievals, while ground based measurements from SHEBA are in between. We discuss these
differences in terms of instrument-, retrieval- and reanalysis
characteristics, which differ substantially between the analyzed
datasets.
9
Francoeur, Mathieu. "NEAR-FIELD RADIATIVE TRANSFER: THERMAL RADIATION, THERMOPHOTOVOLTAIC POWER GENERATION AND OPTICAL CHARACTERIZATION." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/58.
Повний текст джерелаАнотація:
This dissertation focuses on near-field radiative transfer, which can be defined as the discipline concerned with energy transfer via electromagnetic waves at sub-wavelength distances. Three specific subjects related to this discipline are investigated, namely nearfield thermal radiation, nanoscale-gap thermophotovoltaic (nano-TPV) power generation and optical characterization. An algorithm for the solution of near-field thermal radiation problems in one-dimensional layered media is developed, and several tests are performed showing the accuracy, consistency and versatility of the procedure. The possibility of tuning near-field radiative heat transfer via thin films supporting surface phononpolaritons (SPhPs) in the infrared is afterwards investigated via the computation of the local density of electromagnetic states and the radiative heat flux between two films. Results reveal that due to SPhP coupling, fine tuning of near-field radiative heat transfer is possible by solely varying the structure of the system, the structure being the film thicknesses and their distance of separation. The coexistence of two regimes of near-field thermal radiation between two thin films of silicon carbide is demonstrated via numerical simulations and an asymptotic analysis of the radiative heat transfer coefficient. The impacts of thermal effects on the performances of nano-TPV power generators are investigated via the solution of the coupled near-field thermal radiation, charge and heat transport problem. The viability of nano-TPV devices proposed so far in the literature, based on a tungsten radiator at 2000 K and indium gallium antimonide cell, is questioned due to excessive heating of the junction converting thermal radiation into electricity. Using a convective thermal management system, a heat transfer coefficient as high as 105 Wm-2K-1 is required to maintain the junction at room temperature. The possibility of characterizing non-intrusively, and potentially in real-time, nanoparticles from 5 nm to 100 nm in size via scattered surface wave is explored. The feasibility of the characterization framework is theoretically demonstrated via a sensitivity analysis of the scattering matrix elements. Measurements of the scattering matrix elements for 200 nm and 50 nm gold spherical particles show the great sensitivity of the characterization tool, although an ultimate calibration is difficult with the current version of the experimental set-up.
10
Barekat, Atefeh. "Hydrodynamic simulations with a radiative surface." Thesis, Stockholms universitet, Institutionen för astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-90573.
Повний текст джерела
11
Tournadre, Benoît. "Heliosat-V ˸ une méthode polyvalente d’estimation du rayonnement solaire au sol par satellite." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM063.
Повний текст джерелаАнотація:
L'éclairement du Soleil à la surface de la Terre est reconnu comme une variable climatique essentielle par l'Organisation Météorologique Mondiale. Sa connaissance est aussi précieuse pour les sciences du climat que pour le développement d'énergies alternatives aux combustibles fossiles, comme le solaire photovoltaïque. La mesure au sol de ce rayonnement est très clairsemée sur la Terre, d'où l'intérêt de méthodes d'estimation basées sur la télédétection par satellite. Combiner les estimations produites à partir de différents satellites en orbite est une voie pour couvrir au mieux l'information sur tout le globe terrestre. De plus, différentes générations de satellites ont produit une imagerie de la Terre depuis plusieurs décennies, permettant d'estimer de longues séries temporelles du rayonnement solaire, voire d'identifier des variations long terme, un objectif récurrent dans l'étude du changement climatique. Depuis plus de trente ans, les méthodes Heliosat permettent cette estimation, mais elles ont été conçues pour être appliquées à un capteur spécifique en orbite géostationnaire et ont des contraintes limitant leurs champs d'application : la nécessité d'utiliser une longue série temporelle passée (Heliosat, Heliosat-2), ou le besoin de mesures multispectrales (Heliosat-4). Ce travail sur le développement d'une méthode Heliosat-V apporte des éléments de polyvalence à l'estimation satellite par les méthodes dites à "indice d'ennuagement", dans l'objectif de tendre vers une donnée homogène du rayonnement solaire issue de mesures de différents instruments satellites. Deux problèmes sont en particulier considérés pour parvenir à cette estimation : la diversité des capteurs en termes de sensibilités spectrales, et l'influence des géométries de visée et d'éclairement solaire sur les mesures satellites. La méthode s'appuie extensivement sur la modélisation du transfert radiatif dans l'atmosphère dans la gamme spectrale 400-1000 nm pour simuler d'une part les mesures de radiomètres satellites en conditions de ciel clair et d'autre part celles en présence d'un nuage optiquement épais. La méthode est testée sur l'imagerie d'un instrument satellite géostationnaire, Meteosat-9/SEVIRI, et de manière plus exploratoire sur celle d'un non géostationnaire, DSCOVR/EPIC. Les résultats sont comparés à des mesures de référence au sol de l'éclairement, et montrent des performances similaires à celles de produits opérationnels d'éclairement solaire. La qualité des estimations dépend cependant du canal spectral utilisé, en particulier de la présence de diffusion ou d'absorption de l'atmosphère claire dans le signal mesuré par satellite. L'accent est aussi mis sur le besoin d'un étalonnage absolu précis des mesures radiométriques satellites pour produire des séries temporelles d'éclairement de surface avec des biais et une dérive temporelle les plus faibles possiblesSolar irradiance at the surface of the Earth is recognized as an essential climate variable by the World Meteorological Organization. Its knowledge is as much important for climate sciences as for the development of energy alternatives to fossil fuels, like solar photovoltaic. Ground measurements of this radiation are very sparse on Earth, explaining the interest for satellite-based remote sensing to estimate it. Combining estimations from different satellites in orbit is a pathway to cover the information on the whole globe. Different generations of satellites also produced a multidecadal imagery of the Earth, making it conceivable to estimate long time series of solar radiation, or even to identify long-term variations, a recurrent objective in the study of climate change. For more than 30 years, Heliosat methods estimate surface solar irradiance from satellite imagery, but they have been designed to be applied to a specific sensor on a geostationary orbit, and have limitations in their scope : the need for a long archive of satellite imagery (Heliosat, Heliosat-2), or else the need for multispectral measurements (Heliosat-4). This work dedicated to the development of a Heliosat-V method brings elements of versatility to the satellite-based estimation from so-called "cloud-index" methods, with the ultimate goal to reach homogeneous data of solar radiation derived from measurements made by different satellite instruments. Two issues are in particular considered here to reach such an estimation: the diversity of sensors in terms of spectral sensitivities, and the influence of viewing and solar geometries on spaceborne measurements. The method extensively deals with radiative transfer modeling in the spectral range 400-1000 nm to simulate on one hand satellite measurements in clear-sky conditions, and on the other hand satellite measurements in the presence of an optically thick cloud. The method is tested on the imagery of a geostationary satellite instrument, Meteosat-9/SEVIRI, and in a more exploratory way, on the non geostationary sensor DSCOVR/EPIC. Results are compared to high quality ground-based measurements of irradiance, and show performances similar to operational satellite products. However, the quality of estimates depends on the spectral channel used, and especially of the presence of clear-sky atmospheric scattering or absorption in the signal measured by the satellite instrument. The accent is also put on the need for an accurate absolute calibration of satellite radiometric measurements in order to produce time series of surface solar irradiance with the smallest biases and temporal drift possible
12
Basu, Soumyadipta. "Near-field radiative energy transfer at nanometer distances." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31777.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Zhang, Zhuomin; Committee Member: Citrin, David; Committee Member: Hesketh, Peter; Committee Member: Joshi, Yogendra; Committee Member: Peterson, Andrew. Part of the SMARTech Electronic Thesis and Dissertation Collection.
13
Simms, Stephen William. "Microwave radiation control using textured surface substrates." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486194.
Повний текст джерелаАнотація:
The main objective of this work was to study the behaviour of antennas constructed using textured surface substrates, and to a certain extent provide control over their farfield radiation patterns. The properties of the textured surface have been analysed in terms of numerical electromagnetic simulation and by measurement, revealing both artificial magnetic conductor and electromagnetic bandgap properties. It is shown through measurement that by engineering the reflection phase response of such surfaces they can be made to reflect an incident circularly polarised .wave with the same sense as that of the incident polarisation, or with a sense opposite to that of the incident wave. Such properties can be potentially useful in radar cross-section control. Having characterised the textured surface, we then demonstrate its use as an efficient ground plane for a wire dipole. For this structure, we demonstrate that the dipole excites surface currents which, in turn, contribute to the far-field radiation pattern. This is confirmed by the examination of the 'measured near-field and far-field energy distributions close to the antenna. By introducing surface anisotropy to the structure, we further demonstrate far-field radiation pattern control. A novel method of feeding such structures was proposed, using a slot etched in the ground plane, in order to provide excitation to the antenna. Further, we show that careful placement of surface mounted resistors connecting adjacent patches can influence the confinement of surface currents, and as a result produce a more directive radiation pattern. We also show that by selectively interconnecting textured elements, the current distribution can be modified such that we can switch the far-field pattern from sum to difference mode.
14
Dolinar, Erica K., Xiquan Dong, Baike Xi, Jonathan H. Jiang, and Norman G. Loeb. "A clear-sky radiation closure study using a one-dimensional radiative transfer model and collocated satellite-surface-reanalysis data sets." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/622761.
Повний текст джерелаАнотація:
Earth's climate is largely determined by the planet's energy budget, i.e., the balance of incoming and outgoing radiation at the surface and top of atmosphere (TOA). Studies have shown that computing clear-sky radiative fluxes are strongly dependent on atmospheric state variables, such as temperature and water vapor profiles, while the all-sky fluxes are greatly influenced by the presence of clouds. NASA-modeled vertical profiles of temperature and water vapor are used to derive the surface radiation budget from Clouds and Earth Radiant Energy System (CERES), which is regarded as one of the primary sources for evaluating climate change in climate models. In this study, we evaluate the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalyzed clear-sky temperature and water vapor profiles with newly generated atmospheric profiles from Department of Energy Atmospheric Radiation Measurement (ARM)-merged soundings and Aura Microwave Limb Sounder retrievals at three ARM sites. The temperature profiles are well replicated in MERRA-2 at all three sites, whereas tropospheric water vapor is slightly dry below similar to 700 hPa. These profiles are then used to calculate clear-sky surface and TOA radiative fluxes from the Langley-modified Fu-Liou radiative transfer model (RTM). In order to achieve radiative closure at both the surface and TOA, the ARM-measured surface albedos and aerosol optical depths are adjusted to account for surface inhomogeneity. In general, most of the averaged RTM-calculated surface downward and TOA upward shortwave and longwave fluxes agree within similar to 5 W/m(2) of the observations, which is within the uncertainties of the ARM and CERES measurements. Yet still, further efforts are required to reduce the bias in calculated fluxes in coastal regions.
15
Andrews, Timothy. "A surface perspective on radiative forcing of climate." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531644.
Повний текст джерела
16
Berrabah, Nassif. "On High Order On-Surface Radiation Boundary Conditions." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415620836.
Повний текст джерела
17
Monteiro, Manuel Conceição Gonçalves. "Forçamento radiativo à superficie e no topo da atmosfera provocado por nuvens sobre a Região de Évora : Cloud radiative forcing to the surface and in the top of the atmosphere provoked for clouds on the region of Évora." Master's thesis, Universidade de Évora, 2004. http://hdl.handle.net/10174/14850.
Повний текст джерелаАнотація:
Nesta tese investigou-se o papel desempenhado pelas nuvens no balanço radiativo local observado à superfície da Terra. Para tal foram determinados os forçamentos radiativos de pequeno comprimento de onda, de grande comprimento de onda e referentes à banda espectral total devido às nuvens. Recorrendo a imagens de satélite, determinou-se os forçamentos radiativos devido às nuvens, no topo da atmosfera. Foram consideradas as situações de cobertura total de nuvens, ou seja, correspondendo à nebulosidade máxima, N=8. O estudo foi feito de modo a poder contemplar situações distintas de cobertura de nuvens, correspondentes a diferentes tipos de nuvens para a região de Évora. A partir das medidas dos fluxos de radiação solar e da radiação infravermelha observados, desde há vários anos no Centro Geofísico de Évora, com radiómetro de banda larga foi possível determinar, quer o balanço da radiação (solar global, infravermelha ou total, isto é, a soma das duas) como o forçamento radiativo global local à superfície devido à presença de nuvens que cobrem totalmente o céu, sobre o local de observação (Évora). A partir do conhecimento dos forçamentos radiativos devido às nuvens simultaneamente no topo de atmosfera e à superfície foi possível determinar o forçamento radiativo na atmosfera devido às nuvens. O conhecimento do forçamento radiativo na atmosfera devido às nuvens e a sua evolução ao longo de um certo período de tempo permitir-nos-ão ter informação sobre a evolução da energia que é absorvida ou retirada da atmosfera ao longo desse intervalo de tempo.
/*** Abstract - The present thesis consists of the role played by clouds in the local radiative balance observed at Earth surface. They had been determined both the radiative forcing of short and long wave related to the total spectral band provoked by clouds. The clouds radiative forcing in the top of atmosphere was determined by satellite images. The situation of total cloud covering had been corresponding to the maximum cloudiness N=8. The study was made in order to be able to contemplate distinct situations of clouds covering corresponding differents clouds types in Évora region. From the measures of solar radiation and infrared radiation fluxes observed for many years in the Geophysical Centre of Évora , with radiometer of broadband was possible to determine the radiation balance (solar global , infrared or total) as the local global radiative forcing at surface due to cloud presence that covers total sky in Évora region. lt was possible to determine the cloud radiative forcing in the atmosphere by the knowledge simultaneously of the clouds radiative in the top of atmosphere and at the surface. The knowledge of clouds radiative forcing in the atmosphere and its evolution throughout a certain period of time will allow us to have information on the evolution of the energy that absorbed or removed form the atmosphere during this interval of time.
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Libois, Quentin. "Evolution des propriétés physiques de neige de surface sur le plateau Antarctique. Observations et modélisation du transfert radiatif et du métamorphisme." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU026/document.
Повний текст джерелаАнотація:
Le bilan d'énergie de surface du Plateau Antarctique est essentiellement contrôlé par les propriétés physiques des premiers centimètres du manteau neigeux. Or l'évolution de cette neige de surface est complexe car elle dépend de processus fondamentalement imbriqués: vitesse de métamorphisme, profils de température, pénétration du rayonnement solaire, précipitations, transport de neige par le vent, etc. L'objectif de ces travaux de thèse est d'étudier ces diverses composantes et leur couplage afin de simuler l'évolution de la densité de la neige et de la taille de grain (surface spécifique) sur le Plateau Antarctique. Pour représenter de manière physique l'absorption de l'énergie solaire à l'intérieur du manteau, un modèle de transfert radiatif à fine résolution spectrale (TARTES) a été implémenté dans le modèle de manteau neigeux détaillé Crocus. TARTES permet de calculer le profil vertical d'absorption d'énergie dans un manteau stratifié dont les caractéristiques sont connues. Parmi elles, la forme des grains, explicitement prise en compte dans TARTES, a été peu étudiée jusqu'à présent. C'est pourquoi une méthode de détermination expérimentale de la forme optique des grains est proposée et appliquée à un grand nombre d'échantillons de neige. Cette méthode, basée sur des mesures optiques, des simulations TARTES, et l'inférence bayésienne, a permis de déterminer la forme la plus adéquate pour simuler les propriétés optiques de la neige, et a mis en évidence le fait que représenter la neige par un ensemble de particules sphériques conduisait à surestimer la profondeur de pénétration du rayonnement d'environ 30%. L'impact de l'absorption en profondeur du rayonnement sur les profils de température dans le manteau et son métamorphisme est ensuite étudié par des approches analytique et numérique, mettant en valeur la sensibilité des profils aux propriétés de la neige proche de la surface. En particulier, la densité de la neige sur les premiers centimètres est cruciale pour le bilan d'énergie du manteau car elle impacte à la fois la profondeur de pénétration du rayonnement et la conductivité thermique du manteau. Puisque le modèle Crocus tient compte de ce couplage entre propriétés optiques et physiques du manteau, il est utilisé pour estimer l'influence des conditions météorologiques sur la variabilité temporelle des propriétés physiques de la neige de surface à Dôme C. Ces simulations sont évaluées au regard d'un jeu de données collectées lors de missions de terrain et de mesures automatiques de l'albédo spectral et de la pénétration du rayonnement dans la neige. Ces observations mettent en évidence le rôle primordial des précipitations dans les variations rapides de taille de grain en surface et l'existence d'un cycle saisonnier de cette taille de grain. Ces variations sont bien simulées par Crocus lorsque le forçage atmosphérique qui lui est imposé est adéquat. En particulier, l'impact du vent sur l'évolution du manteau est fondamental car il contrôle la densité de surface par le biais du transport de neige. Ce transport est aussi à l'origine de la variabilité spatiale des propriétés de la neige observée à Dôme C. C'est pourquoi une modélisation stochastique de l'érosion et du transport de neige dans Crocus est proposée. En plus d'expliquer la variabilité spatiale de la densité et de la taille de grain, elle permet de reproduire celle de l'accumulation annuelle ainsi que les variations rapides de hauteur de neige liées à des épisodes de vent. Ces travaux ont permis une meilleure représentation des processus physiques qui contrôlent les variations des propriétés de la neige de surface à Dôme C, tout en soulignant le rôle primordial du vent, dont l'impact sur le manteau est particulièrement complexe à simulerThe surface energy balance of the Antarctic Plateau is mainly governed by the physical properties of the snowpack in the topmost centimeters, whose evolution is driven by intricated processes such as: snow metamorphism, temperature profiles variations, solar radiation penetration, precipitation, snow drift, etc. This thesis focuses on the interactions between all these components and aims at simulating the evolution of snow density and snow grain size (specific surface area) on the Antarctic Plateau. To physically model the absorption of solar radiation within the snowpack, a radiative transfer model with high spectral resolution (TARTES) is implemented in the detailed snowpack model Crocus. TARTES calculates the vertical profile of absorbed radiation in a layered snowpack whose characteristics are given. These characteristics include snow grain shape, a parameter that has been seldom studied. For this reason, an experimental method to estimate the optical grain shape is proposed and applied to a large number of snow samples. This method, which combines optical measurements, TARTES simulations and Bayesian inference, is used to estimate the optimal shape to be used in snow optical models. In addition, it highlights that representing snow as a collection of spherical particles results in overestimation of the penetration depth of solar radiation. The influence of the penetration of solar radiation on the snow temperature profiles is then investigated with analytical and numerical tools. The results point out the high sensitivity of the temperature profiles to surface snow physical properties. In particular, the density of the topmost centimeters of the snowpack is critical for the energy budget of the snowpack because it impacts both the effective thermal conductivity and the penetration depth of light. To simulate the evolution of snow physical properties at Dome C by taking into account their interdependence with snow optical properties, the model Crocus is used, driven by meteorological data. These simulations are evaluated against a set of data collected during field missions as well as automatic measurements of snow spectral albedo and penetration depth. These observations highlight the influence of weather conditions on the temporal variability of surface snow properties. They show the existence of a slow decrease of snow grain size at the surface during summer. Rapid changes are also observed, essentially due to precipitation. These variations are well simulated by Crocus when forced by an appropriate atmospheric forcing. In particular, the impact of wind on the evolution of the snowpack is crucial because it controls the surface density through snow transport. This transport is also responsible for the spatial variability of snow properties observed at Dome C. That is why a stochastic representation of snow erosion and transport in Crocus is proposed. It explains well the observations of the spatial variability of density and grain size, and reproduces the variability of the annual accumulation as well as rapid changes in snow height resulting from drift events. This study improves our understanding of the physical processes which drive the properties of snow close to the surface on the Antarctic Plateau, and also points out the critical role of wind, the impact of which is very difficult to account for in models yet
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Roy, Thiery Jacques. "Ionising radiation induced surface effects in charged coupled devices." Thesis, Brunel University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286799.
Повний текст джерела
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Kim, Hye-Yun. "Estimation of land surface radiation budget from MODIS data." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8577.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Geography. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Al, Weshah Adel W. Weshah. "High Order On-Surface Radiation Boundary Conditions in Electromagnetics." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron150212307243821.
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Chia, Yan Wah. "Radiation from curved (conical) frequency selective surfaces." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/7200.
Повний текст джерелаАнотація:
The thesis deals with the analysis of a microwave Frequency Selective Surface (FSS) on a conical dielectric radome illuminated by a feed hom located at the base. Two approaches have been adopted to solve this problem. The first approach is to calculate the element currents under the assumption that the surface is locally flat. Consequently, the element current at that locality can be determined by employing Floquet modal analysis. The local incidence has been modelled from the radiation pattern of the source or the aperture fields of the feed. Three types of feed model were used to account for the field illumination on the radome. The transmitted fields from the curved surface are obtained from the sum of the radiated fields due to the equivalent magnetic and electric current sources distributed in each local unit cell of the conical surface. This method treats the interaction of neighbouring FSS elements only. In the second approach the curvature is taken into account by dividing the each element into segments which conform to the curved surface. An integral formulation is used to take into account the interaction of all the elements. The current source in each FSS element from the formulation is solved using the method of moments (MOM) technique. A linear system of simultaneous equations is obtained from the MOM and has been solved using elimination method and an iterative method which employs conjugate gradients. The performance of both methods has been compared with regard to the speed of computations and the memory storage capability. New formulations using quasi static approximations have been derived to account for thin dielectric backing in the curved aperture FSS analysis. Computer models have been developed to predict the radiation performance of the curved(conical) FSS. Experiments were performed in an anechoic chamber where the FSS cone was mounted on a jig resting on a turntable. The measuring setup contained a sweep oscillator that supplied power to a transmitting feed placed at the base of the cone. Amplitude and phase values of the far field radiation pattern of the cone were measured with the aid of a vector network analyser. Cones with different dimensions and FSS element geometries were constructed and the measured transmission losses and radiation patterns compared with predictions.
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Amos, Terri Emma. "Modelling nanoscale kinetics of radiation damaged surfaces." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10460.
Повний текст джерелаАнотація:
Materials in nuclear reactors and satellites experience continually damaging radiation which leads to their degradation over time. Currently, a materials safe working lifetime within these environments is estimated with a large, costly, safety margin. The work of this thesis aims to improve the usefulness of an optical technique known as reflection anisotropy spectroscopy (RAS), which once fully characterised could allow materials to be actively monitored in such environments. The intrinsic optical anisotropy of the Cu(110) surface has been exploited to study nanoscale kinetics of ion bombarded surfaces. Within the Cu(110) RA spectrum the 2.1eV peak is particularly sensitive to surface defects and largely unaffected by the bulk of the substrate. Using the Poelsema-Comsa model (which assumes defects scatter surface electronic states within a patch centred on the defect) it can be demonstrated that at finite temperatures the decay of the 2.1eV peak contains information relating to the diffusion of surface defects. A kinetic Monte Carlo simulation has been created to model the destruction of this peak and allows further understanding of the diffusion processes involved. The decay of the 2.1eV peak with ion bombardment has been successfully modelled for a range of temperatures using experimental RAS data for comparison. Through a novel way of analysing RAS data, it has been shown that the total scattering cross section per ion impact decreases with bombardment time, which it is believed to be due to surface diffusion. This could give a novel way of measuring surface diffusion directly from RAS measurements. Clustering of ion induced surface defects has been analysed and the results found are consistent with STM images of the same surface obtained 30 minutes after bombardment. While molecular dynamics calculations have previously attempted to predict the surface topology and defect clustering nanoseconds after impact, using a kinetic Monte Carlo simulation improves on this, demonstrating that diffusion on long time scales (currently inaccessible using molecular dynamics calculations) play an important role in predicting nano-surface topology. 2.1eV peak recovery after surface damage by ion bombardment was also investigated. The peak was found to recover at finite temperatures, which is also seen in experimental data. It was concluded that the surface diffusivity values in the literature are too high and a new value for diffusivity has been calculated by comparing simulation and experimental data.
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Roupioz, Laure. "Modélisation et suivi de l'éclairement et de l'albédo de surface à partir de données satellitaires : le cas du Tibet." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAD022/document.
Повний текст джерелаАнотація:
Le suivi journalier du bilan radiatif solaire est indispensable à l’étude des processus à l'interface sol-atmosphère, en particulier en climatologie et en hydrologie. Dans le cadre du projet CEOP-Aegis visant à étudier l'hydrologie du plateau du Tibet, cette thèse se concentre sur le développement d'une méthode permettant d’en estimer le bilan radiatif solaire de surface de façon quotidienne. Une série temporelle de flux radiatifs produite à partir de produits satellitaires existants met en évidence la nécessité d’intégrer la variabilité sous-pixel du terrain et des nuages pour les zones aussi hétérogènes que le Tibet. L’analyse de l’impact de la variabilité spatiale et temporelle des nuages sur le rayonnement solaire illustre le bénéfice lié à l’utilisation de la répartition des nuages plutôt que la fraction de nébulosité et l’importance d’une résolution temporelle élevée. Une méthode novatrice proposée pour la correction topographique sous-pixel montre que l’utilisation d’un modèle numérique de terrain à haute résolution spatiale améliore significativement l'estimation de l’éclairement ainsi que de l'albédo. Deux approches sont proposées pour améliorer l’estimation du bilan radiatif intégrant de manière adéquate l’hétérogénéité sous-pixelMonitoring the solar radiation budget on a daily basis is a prerequisite to study land surface processes, especially in climatology and hydrology. As part of the CEOP-Aegis project studying the hydrology of the Tibetan Plateau, this thesis focuses on developing a method to adequately estimate at-surface daily solar radiation budget over this particular area. A radiation budget time series produced based on existing satellite data products highlights the necessity to consider terrain and clouds sub-pixel variability when working over heterogeneous areas such as the Tibetan Plateau. The analysis of the impact of spatial and temporal variability of clouds on solar radiation demonstrates that the surface irradiance estimation would benefit from using cloud distribution instead of cloud fraction and the significance of high temporal resolution. A new sub-pixel topographic correction method is proposed and shows that using high resolution digital elevation model improves the irradiance as well as the albedo retrieval. Two approaches are proposed to improve solar radiation budget estimates taking into account adequately the sub-pixel heterogeneity
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Hermozo, Laura. "L'estimation de la correction troposphérique humide pour l'altimétrie spatiale : l'approche variationnelle." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30026/document.
Повний текст джерелаАнотація:
L'altimétrie spatiale contribue majoritairement à la compréhension de la circulation océanique régionale et globale. Elle permet aujourd'hui de fournir une cartographie de la topographie océanique à des échelles spatiales et temporelles de plus en plus fines. Le passage du signal radar à travers la vapeur d'eau de l'atmosphère implique un retard de l'onde, qui nécessite d'être corrigé : c'est la correction troposphérique humide. Des méthodes statistiques sont actuellement utilisées pour estimer la correction troposphérique humide. Elles permettent d'inverser des mesures de températures de brillance fournies par un radiomètre couplé à l'altimètre sur une mission altimétrique, à deux ou trois fréquences proches de la bande d'absorption de la vapeur d'eau, à 22.235 GHz. Bien que ces algorithmes permettent d'estimer cette correction avec de faibles incertitudes en plein océan, des améliorations sont nécessaires pour réduire les erreurs dans les zones océaniques complexes, comme les régions d'upwelling, et sur les surfaces hétérogènes, comme en régions côtières, sur glace de mer, ou sur les eaux continentales. A ces fins, une approche variationnelle uni-dimensionnelle (1D-Var) est développée dans cette thèse. Elle permet de tenir compte de la physique de l'atmosphère et des variations de la surface dans l'environnement des mesures, pour estimer la correction troposphérique de manière globale, sur différents types de surface, dans le contexte des missions altimétriques actuelles, et futures, dont les technologies instrumentales évoluent. Une analyse fine des caractéristiques de l'approche 1D-Var, et de ses performances, permet de montrer l'apport et l'impact des différents paramètres en jeu sur les variables atmosphériques restituées, et la correction troposphérique humide estimée. Les performances du 1D-Var ainsi que ses limites sont évaluées pour l'estimation la correction troposphérique humide en plein océan, en conditions de ciel clair. L'apport des mesures de températures de brillance aux hautes fréquences, typiques des missions altimétriques futures, est également analysé. Leur potentiel est exploité dans le cadre de l'estimation de la correction troposphérique humide dans les régions côtières, où les mesures de températures de brillance sont contaminées par la présence de terre dans le signal. Enfin, une analyse des estimations des émissivités de surface, et de leurs variations sur la glace de mer, est proposée dans le cadre d'une étude préliminaire à l'estimation de la correction troposphérique humide, aux interfaces complexes mer/glace de mer, dans les régions polairesSpace altimetry is one of the major contributors to the understanding of regional and global oceanic circulation. It currently enables to provide a map of ocean topography at higher temporal and spacial scales. A propagation delay of the altimeter signal along its path through atmospheric water vapor needs to be accounted for, and corresponds to the wet tropospheric correction. Statistical methods are currently used to estimate wet tropospheric correction. These methods are fed by brightness temperature measurements provided by a radiometer coupled to the altimeter, at two or three frequencies close to the water vapor absorption line, at 22.235 GHz. While these algorithms provide wet tropospheric correction with low uncertainties over open ocean, improvements are still needed to reduce higher uncertainties in complex oceanic areas, such as upwelling regions, and over heterogeneous surfaces, as coastal regions, sea ice or inland waters. To this end, a one-dimensional variational approach (1D-Var) is developed in the frame of this thesis. This approach accounts for atmospheric and surface variability in the surroundings of the measurements, to provide wet tropospheric correction estimates at a global scale, over various surfaces, in the context of both current and future altimetry missions, with improved instrumental technologies. We first analyze the characteristics of the 1D-Var approach and evaluate its performances. The contribution and impact of the different input parameters on retrieved atmospheric variables and wet tropospheric correction are shown through this analysis. The potential and limits of the 1D-Var approach to retrieve wet tropospheric correction over open ocean, for clear sky conditions, are evaluated. The contribution of high frequencies, typical to future altimetry missions, is also analyzed. It is fully exploited to retrieve wet tropospheric correction over coastal areas, where land contamination occurs within brightness temperature measurements. A preliminary analysis of surface emissivity estimates and their variability over sea ice is also undertaken, in the frame of the 1D-Var estimation of wet tropospheric correction over sea ice/open sea transition surfaces, in polar areas
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Koudogbo, Fifamè N. "Etude des diffusions de surface et de volume par une surface rugueuse diélectrique : calcul des interactions entre un objet 3D et une surface naturelle." Toulouse 3, 2002. http://www.theses.fr/2002TOU30155.
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Cantono, Giada. "Relativistic Plasmonics for Ultra-Short Radiation Sources." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS353/document.
Повний текст джерелаАнотація:
La plasmonique étudie le couplage entre le rayonnement électromagnétique et les oscillations collectives des électrons dans un matériel. Les plasmons de surface (SPs), notamment, ont la capacité de concentrer le champ électromagnétique sur des distances micrométriques, ce qui les rend intéressants pour le développement des dispositifs photoniques les plus novateurs. 'Etendre l'excitation de SPs au régime de champs élevés, où les électrons oscillent à des vitesses relativistes, ouvre des perspectives stimulantes pour la manipulation de la lumière laser ultra-intense et le développement de sources de rayonnement énergétiques et à courte durée. En fait, l'excitation de modes résonnants du plasma est l'une des stratégies possibles pour transférer efficacement l'énergie d'une impulsion laser ultra-puissante à une cible solide, cela étant parmi les défis actuels dans la physique de l’interaction laser-matière à haute intensité. Dans le cadre de ces deux sujets, ce travail de thèse démontre la possibilité d'exciter de façon résonnante des plasmons de surface avec des impulsions laser ultra-intenses. Elle étudie comment ces ondes peuvent à la fois accélérer de paquets d'électrons relativistes le long de la surface de la cible mais aussi augmenter la génération d'harmoniques d'ordre élevé de la fréquence laser. Ces deux processus ont été caractérisés avec de nombreuses expériences et simulations numériques. En utilisant un schéma d’interaction standard de la plasmonique classique, les SPs sont excités sur des cibles dont la surface présente une modulation périodique régulière à l'échelle micrométrique (cibles réseau). Dans ce cas, les propriétés de l'émission d'électrons tout comme celles des harmoniques permettent d’envisager leur utilisation dans des application pratiques. En réussissant à dépasser les principaux problèmes conceptuels et techniques qui jusqu'au présent avaient empêché l'application d'effets plasmoniques dans le régime de champs élevés, ces résultats apportent un intérêt nouveau à l'exploration de la Plasmonique RelativistePlasmonics studies how the electromagnetic radiation couples with the collective oscillations of the electrons within a medium. Surface plasmons (SPs), in particular, have a well-established role in the development of forefront photonic devices, as they allow for strong enhancement of the local EM field over sub-micrometric dimensions. Promoting the SP excitation to the high-field regime, where the electrons quiver at relativistic velocities, would open stimulating perspectives for the both the manipulation of ultra-intense laser light and the development of energetic, short radiation sources. Indeed, the excitation of resonant plasma modes is a possible strategy to efficiently deliver the energy of a high-power laser to a solid target, this being among the current challenges in the physics of highly-intense laser-matter interaction. Gathering these topics, this thesis demonstrates the opportunity of resonant surface plasmon excitation at ultra-high laser intensities by studying how such waves accelerate bunches of relativistic electrons along the target surface and how they enhance the generation of high-order harmonics of the laser frequency. Both these processes have been investigated with numerous experiments and extensive numerical simulations. Adopting a standard configuration from classical plasmonics, SPs are excited on solid, wavelength-scale grating targets. In their presence, both electron and harmonic emissions exhibit remarkable features that support the conception of practical applications. Putting aside some major technical and conceptual issues discouraging the applicability of plasmonic effects in the high-field regime, these results are expected to mark new promises to the exploration of Relativistic Plasmonics
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Voogt, James Adrian. "Validation of an urban canyon radiation model for nocturnal long-wave radiative fluxes and the effect of surface geometry on cooling in urban canyons." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27679.
Повний текст джерелаАнотація:
The urban canyon radiation model of Arnfield (1976, 1982) is validated using measurements of long-wave fluxes taken within a scale urban canyon constructed from concrete building blocks. A custom-designed traversing system allowed miniature radiometers to be automatically moved around the perimeter of a canyon cross-section thereby providing for the validation of individual model grid-points.
Measured model input consists of surface temperatures obtained using fine wire themocouples, incident long-wave radiation at the canyon top, and emissivity of canyon materials. Tests were conducted to establish the expected accuracy and precision of the input data. Surface temperature data were filtered to remove a noise component. A probable error analysis of all measured model input and validation data is made.
Sensitivity tests of the model to variations in input data are presented. Surface temperature is the dominant control under the conditions tested. Model-calculated view-factors are shown to be in error for adjacent corner points and are replaced with view-factors calculated using equations derived from the Nusselt Unit Sphere method (Steyn, pers. comm.)
Validation results for a range of canyon height-to-width ratios, meteorological conditions and model parameters are presented. Excellent agreement between modelled and measured fluxes is obtained for points on the canyon floor and top. The agreement for fluxes at points on the canyon walls is generally good but is shown to suffer from errors in sensor orientation relative to the canyon walls. Use of the Unsworth and Monteith (1975) radiance distribution improves model performance statistics for incident and net long-wave radiation.
Four different estimates of surface temperature are used as model input in place of the measured values to investigate the differences in the model output. Surface temperature-based estimates are found to be superior to those based upon air temperature. The use of unmodified screen-level air temperatures measured at Vancouver Airport produces the poorest agreement.
The temporal and spatial variation of in-canyon temperatures and radiation are presented for three canyon height-to-width ratios. The canyon geometry is shown to significantly reduce the surface cooling on the canyon floor compared to an open site under ideal radiative cooling conditions. Results are compared to previous results from scale models (Oke, 1981) and field studies (Oke and Maxwell, 1975; Hogstrdm et al., 1978). . Atmospheric controls of incident long-wave radiation, wind speed and direction are also shown to affect the observed cooling.Arts, Faculty of
Geography, Department of
Graduate
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Galloway, Christopher. "Non-radiative processes and vibrational pumping in surface-enhanced raman scattering : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Physics /." ResearchArchive@Victoria e-Thesis, 2010. http://hdl.handle.net/10063/1244.
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Marty, Christoph. "Surface radiation, cloud forcing and greenhouse effect in the Alps /." Zürich, 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13609.
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Liu, Hongqing. "Global scale aerosol properties implications for surface shortwave radiation budget /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3154.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Meteorology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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MacManus, Liam Francis. "Surface modification studies of polypropylene using ultraviolet radiation and ozone." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32497.pdf.
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Hart, Quinn James 1965. "Surface and aerosol models for use in radiative transfer codes." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277334.
Повний текст джерелаАнотація:
Absolute radiometric calibrations of Landsat 5 Thematic Mapper satellite are improved with the inclusion of a method to invert optical depth measurements to obtain an aerosol particle size distribution and a non-lambertian surface reflectance model. Also, a program is developed to improve speed and standardization of the entire calibration procedure. The inverted size distributions can predict radiances varying from the previous jungian distributions by as much as 5 percent, though the reduction in the estimated error is less than one percent. An empirical model for the surface reflection of White Sands using a two-degree polynomial fit as a function of scattering angle was employed. The model reduced estimated errors in radiance predictions by up to one percent. Satellite calibrations dating from October, 1984 are reprocessed using the improved methods and a linear estimation of satellite counts per unit radiance versus time since launch is determined.
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Psihogios, Panagiotis. "Thermal images of sky and sea-surface background infrared radiation." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23425.
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Smith, Malcolm Gordon. "Sound radiation from a vibrating surface under a boundary layer." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398608.
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Baier, Florian. "Noise Radiation from a Supersonic Nozzle with Jet/Surface Interaction." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1617108352134538.
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Lee, Hyunjin. "Radiative properties of silicon wafers with microroughness and thin-film coatings." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07092006-181152/.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Zhang, Zhuomin, Committee Chair ; Joshi, Yogendra, Committee Member ; Lee, Kok-Meng, Committee Member ; Gallivan, Martha, Committee Member ; Zhao, Yiping, Committee Member.
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Huie, Keith C. "Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/30898.
Повний текст джерелаАнотація:
The purpose of this thesis is to investigate a novel method to develop broadband microstrip (patch) antennas using substrates containing photonic crystals. Photonic crystals are a class of periodic dielectric, metallic, or composite structures that when introduced to an electromagnetic signal can exhibit a forbidden band of frequencies (or bandgap) in which the incident signal destructively interferes and thus is unable to propagate. It is proposed that such photonic crystals will reduce surface waves and prohibit the formation of substrate modes, which are commonly known inhibitors of patch antenna designs. By reducing or eliminating the effects of these electromagnetic inhibitors with photonic crystals, a broadband response can be obtained from inherently narrowband antennas. In addition, it is also proposed that the behavior of the photonic crystals will lead to a reduction in pattern sidelobes resulting in improvements in radiation pattern front-to-back ratio and overall antenna efficiency. This research is verified through analytical simulations and experimental investigations in the Virginia Tech anaechoic chamber.Master of Science
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Li, Xianming. "The effect of gas-surface interactions on radiative ignition of PMMA." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15888.
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Ruckstuhl, Christian. "Surface radiation changes and their impact on climate in Central Europe." Zürich, 2008. http://e-collection.ethbib.ethz.ch/view/eth:30426.
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El-Nimri, Salem. "DEVELOPMENT OF AN IMPROVED MICROWAVE OCEAN SURFACE EMISSIVITY RADIATIVE TRANSFER MODEL." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2878.
Повний текст джерелаАнотація:
An electromagnetic model is developed for predicting the microwave blackbody emission from the ocean surface over a wide range of frequencies, incidence angles, and wind vector (speed and direction) for both horizontal and vertical polarizations. This ocean surface emissivity model is intended to be incorporated into an oceanic radiative transfer model to be used for microwave radiometric applications including geophysical retrievals over oceans. The model development is based on a collection of published ocean emissivity measurements obtained from satellites, aircraft, field experiments, and laboratory measurements. This dissertation presents the details of methods used in the ocean surface emissivity model development and comparisons with current emissivity models and aircraft radiometric measurements in hurricanes. Especially, this empirically derived ocean emissivity model relates changes in vertical and horizontal polarized ocean microwave brightness temperature measurements over a wide range of observation frequencies and incidence angles to physical roughness changes in the ocean surface, which are the result of the air/sea interaction with surface winds. Of primary importance are the Stepped Frequency Microwave Radiometer (SFMR) brightness temperature measurements from hurricane flights and independent measurements of surface wind speed that are used to define empirical relationships between C-band (4 Â 7 GHz) microwave brightness temperature and surface wind speed. By employing statistical regression techniques, we develop a physical-based ocean emissivity model with empirical coefficients that depends on geophysical parameters, such as wind speed, wind direction, sea surface temperature, and observational parameters, such as electromagnetic frequency, electromagnetic polarization, and incidence angle.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Kjelgaard, Khin. "Radiation-induced desorption and surface modification in dielectric single crystal materials." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Dissertations/Fall2004/K%5FKjelgaard%5F110204.pdf.
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Korsmeyer, F. Thomas. "The first- and second-order transient free-surface wave radiation problems." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14728.
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Glassford, Eric. "Comparison of Grab, Air, and Surface Results for Radiation Site Characterization." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307442130.
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Prussing, Keith F. "An investigation of surface shape effects on near-field radiative transfer." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54321.
Повний текст джерелаАнотація:
It has been shown that the energy exchange between two objects can be
greatly enhanced when the separation between the objects is on the order
of the wavelength of thermal emission. The earliest theoretical and
computational work focused on simple planar and spherical geometries, or
they resorted to approximations that separated the object to outside of
the thermal wavelength \(\lambda_T = hc/(k_BT)\). Since those original
works, the study of near-field energy exchange has expanded to object
shapes that can be described by a separable coordinate system using a
spectral expansion of the dyadic Green function of the system. The
boundary element method has also been used to study arbitrary shapes in
thermal equilibrium. Application of these new expansion methods to
general shapes out of thermal equilibrium will facilitate in the
optimization of nanoscale structures.
A three step process is used to investigate the effects of object shape
on the total and directionality of the energy exchange between objects.
First, a general expression for the energy flux between the objects will
be formulated. Second, a computational method to evaluate the
expression will be implemented. Finally, the effects of varying the
surface geometry will be explored.
The computational results demonstrate that the total energy exchange
between two bodies is influenced by the surface shape of the objects
even when the surface areas are held constant. While the primary
increase over the classical blackbody energy exchange \(\sigma T^4 A\)
is primarily governed by separation of the surfaces, we show that the
view factors from classical far-field radiative transfer can be used to
predict the change in the total energy exchange from a reference
configuration at the same separation when the surface area of the two
objects is comparable. Additionally, we demonstrate that the spatial
distribution of the energy exchange can be localized into small spatial
region with a peak value increased over \SI{30}{\percent} by using two
objects with dramatically different projected areas.
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Melais, Sergio E. "A quasi Yagi antenna with end fire radiation over a metal ground." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003246.
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Handrup, Karsten. "Synchrotron radiation based studies of complex molecules on surfaces." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/13988/.
Повний текст джерелаАнотація:
In this thesis two single molecule magnets based on the dodecamanganese (III, IV) cluster, with either benzoate or terphenyl-4-carboxylate ligands have been studied on the Au(111) and rutile TiO2(110) surfaces. We have used in situ electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. X-ray absorption spectroscopy measured at the Mn L-edge (Mn 2p) has been used to study the effect of adsorption on the oxidation states of the manganese atoms in the core. In the case of the enzoate-functionalized complex, reduction of the manganese metal centres is observed due to the interaction of the manganese core with the underlying surface. In the case of terphenyl-4 carboxylate, the presence of this much larger ligand prevents the magnetic core from interacting with either the gold or the titanium dioxide surfaces and the characteristic Mn3+ and Mn4+ oxidation states necessary for magnetic behaviour are preserved. In contrast to the single molecule magnets where no charge transfer between the molecules and the substrates or within the molecules themselves were wanted, the molecules of bi isonicotinic acid and the giant zinc porphyrin nanorings have been studied on rutile TiO2(110) and Au(111) surfaces in the pursuit of charge transfer. In the case of the bi-isonicotinic acid it is studied on the rutile TiO2(110) where the technique of resonant inelastic X-ray scattering was been employed. Here we introduce the core-hole clock implementation to estimate the charge transfer from the molecule to the substrate. We verify previous results of ultrafast charge transfer in the sub-femtosecond regime (2.9 ± 0.3 femtoseconds) out of the LUMO+1 orbital. When the higher lying state of the LUMO+2 state is probed charge transfer out of this state and to the substrate is possibly there, but it is not possible to resolve it since it is masked by other effects originating from the inelastic scattering of the system. Furthermore, we see potential charge transfer within the molecule itself and new states observed in the inelastic scattering. Finally, zinc porphyrin nanorings were investigated on two surfaces of rutile TiO2(110) and Au(111). The techniques used here were X-ray photoemission spectroscopy and resonant photoemission spectroscopy. When the rutile TiO2(110) surface was employed hardly any participator decay was present suggesting charge transfer within the molecule itself or to the surface. This is further backed up by the fact that all of the core-excited unoccupied states are found to overlap energetically with the unoccupied states of the substrate, facilitating charge transfer out all the core-excited states. In the case of the Au(111) surface somewhat similar results are found, having all the core-excited states of the molecule located within the unoccupied states of the substrate, which again will facilitate charge transfer out all the core-excited states of the molecule. When the Au(111) substrate was employed the technique of near edge X-ray absorption fine structure was used to investigate the geometric orientation of the molecule on the surface. With the result of 86◦ ± 10◦ to the surface normal we verify previous scanning tunneling microscopy measurement that the zinc porphyrin nanorings will take a at lying orientation on the gold substrate.
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Oliveira, Luciana C. "Gas-phase surface oxidation and chlorination of carbon nanotubes /." Online version of thesis, 2009. http://hdl.handle.net/1850/10931.
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Phantkankum, Nuttapong. "Development of a Low Energy Electron Accelerator System for Surface Treatments and Coatings." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1450732635.
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Andrieu, François. "Caractérisation des surfaces glacées de Mars par imagerie hyperspectrale : inversion du transfert radiatif." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS178/document.
Повний текст джерелаАнотація:
La planète Mars est le siège d'un climat complexe, caractérisé par des cycles du dioxyde de carbone et de l'eau, ainsi qu'un transport de poussière à toutes les échelles. Ces cycles se manifestent par la condensation saisonnière aux pôles de dépôts de glace de CO₂ et d'eau pendant la nuit polaire, et leur sublimation pendant le printemps local. Les cycles du CO₂ , de l'eau et des poussières sur Mars sont intimement liés. Un processus saisonnier actif illustre bien ces liens : les jets de gaz froid, déclenchés par la sublimation saisonnière des dépôts de CO₂ , pouvant mettre en suspension des poussières du régolite de manière durable dans l'atmosphère, et dont l'activité semble être modulée par les échanges d'eau à la surface.L'objectif de cette thèse est de permettre l'utilisation des données d'imagerie hyperspectrale disponibles au maximum de leur potentiel, pour apporter de nouvelles contraintes sur les échanges saisonniers entre surface et atmosphère et sur les interactions entre les différents cycles (CO₂ , eau, poussières), en se focalisant sur les jets de gaz froid. Pour cela, un modèle semi-analytique de transfert radiatif dans les glaces compactes, ainsi qu'une méthode efficace d'inversion ont été développés et validés.Le modèle de transfert radiatif permet de décrire l'interaction de la lumière avec une couche de glace de manière quantitative d'après les paramètres suivants : épaisseur de la couche, proportions volumiques et tailles des impuretés, rugosité de la surface. Il repose sur plusieurs hypothèses majeures : optique géométrique, milieux continus par morceaux, inclusions quasi-sphériques. L'approximation des deux flux est utilisée pour le transfert au sein de la couche mais la réflexion spéculaire en surface est estimée en tenant compte de la variabilité des facettes de la rugosité surfacique. Ce modèle a été validé numériquement et sur des données de laboratoire et des tests numériques. La méthode d'inversion consiste à créer des bases de données synthétiques d’après le modèle de transfert radiatif pour déterminer les jeux de paramètres les plus probables pour reproduire une mesure donnée. L'inversion repose sur le formalisme bayésien : les grandeurs manipulées sont décrites par des densités de probabilités. Ceci permet la prise en compte de manière réaliste des incertitudes sur la donnée et le calcul d'une incertitude a posteriori sur le résultat de l'inversion.Une étude ciblée d'un site d'intérêt a été menée pour tester et démonter l'applicabilité de cette démarche à l'inversion massive de données de spectro-imagerie.Nous avons déterminé l’état de surface du champ de dunes du cratère de Richardson (72°S, 180°W), choisi car il présente de fortes interactions entre cycle de l'eau et du CO₂ , une important activité saisonnière de jets froids mais aussi une grande quantité de données disponible et une haute qualité du suivi temporel. Le suivi des caractéristiques de surface sur ce site montre une diminution de l'épaisseur de la couche de glace pendant le printemps cohérente avec les estimations des modèles de climat. Nous avons pu estimer et faire le suivi du contenu en eau et en poussière pour discuter le scénario de formation des jets froids. Nous avons proposé un nouveau mécanisme de mise en suspension des petits grains d’eauMars has a complex climate, characterized by carbon dioxide and water cycles, and dust transport at all scales. These cycles are mainly controlled by the seasonal condensation of CO₂ and water ice deposits at high latitudes during the polar night and their sublimation during the local spring. There are a lot of interactions between the CO₂ , water and dust cycles on Mars and they influence each other. An active seasonal process illustrates particularly well these links: the cryoventing, cold CO₂ gas jets triggered by seasonal sublimation of CO₂ deposits, which can put dust from the regolith in suspension into the atmosphere durably, and whose activity seems to be modulated by the exchange of water at the surface.The purpose of this thesis is to allow the use of the available hyperspectral imaging data to their full potential, to bring new constraints on seasonal exchanges between surface and atmosphere and the interactions between the different cycles (CO₂ , water , dust), focusing on cold gas jets. To achieve this, a semi-analytical radiative transfer model in compact ices and an effective inversion method were developed and validated.The radiative transfer model describes the interaction of light with a surface quantitatively, using the following parameters: thickness of the layer, volume proportions and grain-sizes of impurities, surface roughness. It is based on several key assumptions: geometrical optics, piecewise-continuous media quasi-spherical inclusions. The two-stream approximation is used for the radiative transfer inside the layer, but the surface specular reflectance is estimated taking into account the variability of the facets orientations from the surface roughness. This model was validated both numerically and on laboratory data.The inversion method consists in exploring synthetic databases generated by the radiative transfer model and determining the most likely sets of parameters to reproduce a given measure. The inversion is based on the Bayesian formalism: the manipulated variables are described by probability density functions. This allows to take into account realistic uncertainties on the data and enables to calculate a posteriori uncertainties on the result of the inversion.A focused study was conducted on a area of particular interest, to test and prove the applicability of this approach to the massive inversion of spectro-imaging data. The dune-field of Richardson Crater (72°S, 180°W) was chosen because it shows strong interactions between the water and CO₂ cycles, a major seasonal cryoventing activity, but also a large amount of data available and a high quality temporal monitoring. The monitoring of surface characteristics on this site shows a decrease in the thickness of the ice during the spring consistently with climate models simulations. We were able to estimate and monitor the content of water and dust in order to discuss the formation scenario of cold jets