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Abedigamba, Oyirwoth Patrick. "The structure of the Large Magellanic Cloud." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/13514.
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Includes bibliographical references (leaves 67-69).<br>This work gives an account of the study of the metallicity [Fe/H] distribution (gradient) in the oldest population in the Large Magellanic Cloud (LMC), by making use of the available RR Lyrae data from the Optical Gravitational Lensing Experiment III (OGLE III). RR Lyrae stars are amongst the oldest objects in the universe and they have a range in element (metal) abundances. Measuring the distribution of metallicities of RR Lyrae stars in a galaxy gives one clues to the origin of galaxies. It is known that the pulsation periods of RR Lyraes is broadly correlated with their metallicity. This fact has been used for investigating the metallicity distribution of RR Lyrae stars in the LMC. I have found an indication that the proportion of metal poor RR Lyrae stars increases with distance from the centre of the LMC. In addition, an attempt was made to improve the metallicity-period relation by introducing the Fourier parameters, but this was unsuccessful. Lastly, a comparison is made with estimates of metallicity gradients of other LMC populations.
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Song, Shi. "The Spectral Signature of Cloud Spatial Structure in Shortwave Radiation." Thesis, University of Colorado at Boulder, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10151129.
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<p> In this thesis, we aim to systematically understand the relationship between cloud spatial structure and its radiation imprints, i.e., three-dimensional (3D) cloud effects, with the ultimate goal of deriving accurate radiative energy budget estimates from space, aircraft, or ground-based observations under spatially inhomogeneous conditions. By studying the full spectral information in the measured and modeled shortwave radiation fields of heterogeneous cloud scenes sampled during aircraft field experiments, we find evidence that cloud spatial structure reveals itself through spectral signatures in the associated irradiance and radiance fields in the near-ultraviolet and visible spectral range.</p><p> The spectral signature of 3D cloud effects in irradiances is apparent as a domain- wide, consistent correlation between the magnitude and spectral dependence of net horizontal photon transport. The physical mechanism of this phenomenon is molecular scattering in conjunction with cloud heterogeneity. A simple parameterization with a single parameter ϵ is developed, which holds for individual pixels and the domain as a whole. We then investigate the impact of scene parameters on the discovered correlation and find that it is upheld for a wide range of scene conditions, although the value of ϵ varies from scene to scene.</p><p> The spectral signature of 3D cloud effects in radiances manifests itself as a distinct relationship between the magnitude and spectral dependence of reflectance, which cannot be reproduced in the one-dimensional (1D) radiative transfer framework. Using the spectral signature in radiances and irradiances, it is possible to infer information on net horizontal photon transport from spectral radiance perturbations on the basis of pixel populations in sub-domains of a cloud scene.</p><p> We show that two different biases need to be considered when attempting radiative closure between measured and modeled irradiance fields below inhomogeneous cloud fields: the remote sensing bias (affecting cloud radiances and thus retrieved properties of the inhomogeneous scene) and the irradiance bias (ignoring 3D effects in the calculation of irradiance fields from imagery-based cloud retrievals). The newly established relationships between spatial and spectral structure lay the foundation for first-order corrections for these 3D biases within a 1D framework, once the correlations are explored on a more statistical basis.</p>
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Giles, Rohini. "Jupiter's tropospheric composition and cloud structure from 5-μm spectroscopy". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:04619240-ba40-4ee2-afcc-7f911f364d05.
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This thesis uses infrared observations from spacecraft and ground-based telescopes to investigate the composition and cloud structure of the jovian atmosphere. It focuses on a single spectral region, known as the 5-μm window, where Jupiter's upper atmosphere becomes optically thin. This allows us to probe down beneath the planet's thick cloud decks to the 4{8 bar region in the middle troposphere. Two different data sources are combined to build up a three-dimensional picture of Jupiter's troposphere. The first dataset is from the Cassini VIMS instrument, and was taken during the 2000-2001 Jupiter yby. These observations cover a wide spectral range, provide global coverage and include both the nightside and the dayside of the planet, making them well suited to studying clouds. The VIMS spectra can be modelled using a single tropospheric cloud deck, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; and (iii) the cloud is sufficiently spectrally at. The second dataset is from the CRIRES instrument at the Very Large Telescope in Chile. These observations have a very high spectral resolution, allowing the absorption lines of individual molecular species to be resolved. The CH<sub>3</sub>D line shape varies between belts and zones, which can be interpreted as variations in the opacity of a deep cloud, located at around 5 bar. There is also evidence for spatial variability in two disequilibrium species, AsH<sub>3</sub> and PH<sub>3</sub>, both of which show an enhancement at high latitudes. This is in contrast to a third disequilibrium species, GeH4, which shows no evidence for spatial variability. The CRIRES dataset also includes several strong emission lines, which are identified as H<sub>3</sub><sup>+</sup>, an auroral species in Jupiter's ionosphere. The strengths of these lines were measured in order to determine the ionospheric temperatures. The work in this thesis contributes to our understanding of the dynamical, chemical and cloud-forming processes shaping Jupiter's troposphere and provides a reference point for future work, including observations made by NASA's Juno mission.
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Lloyd, P. E. "Tropospheric sounding from the TIROS-N series of satellites." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379918.
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Lewtas, Joan. "Radio structure and associated molecular environment at the galactic centre." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.346434.
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Hatzidimitriou, D. "The evolution and geometry of the oouter parts of the Small Magellanic Cloud." Thesis, University of Edinburgh, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234097.
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Horner, Michael S. "Determining the fine structure of the entrainment zone in cloud-topped boundary layers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FHorner.pdf.
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Abreu, Vicente Jorge [Verfasser], and Thomas [Akademischer Betreuer] Henning. "Molecular Cloud Structure at Galactic Scales / Jorge Abreu Vicente ; Betreuer: Thomas Henning." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180739663/34.
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Hill, Peter. "Representing cloud structure in the radiation scheme of the Met Office model." Thesis, University of Reading, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654496.
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Metzger, Eric L. "The relationship between total cloud lightning behavior and radar derived thunderstorm structure." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FMetzger.pdf.
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Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2010.<br>Thesis Advisor: Nuss, Wendell. Second Reader: Pfeiffer, Karl. "March 2010." Author(s) subject terms: Total cloud lightning, thunderstorm structure, hail, severe wind(s), tornadoes, lightning jumps, lightning detection, Lightning behavior, radar derived thunderstorm structure. Includes bibliographical references (p. 83-85). Also available in print.
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Muraveva, Tatiana <1986>. "Improving the cosmic distance ladder. Distance and structure of the Large Magellanic Cloud." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6733/.
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The Large Magellanic Cloud (LMC) is widely considered as the first step of the cosmological distance ladder, since it contains many different distance indicators. An accurate determination of the distance to the LMC allows one to calibrate these distance indicators that are then used to measure the distance to far objects.
The main goal of this thesis is to study the distance and structure of the LMC, as traced by different distance indicators. For these purposes three types of distance indicators were chosen: Classical Cepheids,``hot'' eclipsing binaries and RR Lyrae stars. These objects belong to different stellar populations tracing, in turn, different sub-structures of the LMC. The RR Lyrae stars (age >10 Gyr) are distributed smoothly and likely trace the halo of the LMC. Classical Cepheids are young objects (age 50-200 Myr), mainly located in the bar and spiral arm of the galaxy, while ``hot'' eclipsing binaries mainly trace the star forming regions of the LMC. Furthermore, we have chosen these distance indicators for our study, since the calibration of their zero-points is based on fundamental geometric methods. The ESA cornerstone mission Gaia, launched on 19 December 2013, will measure trigonometric parallaxes for one billion stars with an accuracy of 20 micro-arcsec at V=15 mag, and 200 micro-arcsec at V=20 mag, thus will allow us to calibrate the zero-points of Classical Cepheids, eclipsing binaries and RR Lyrae stars with an unprecedented precision.
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Higgins, Stephen William. "Numerical simulations of jet-cloud collisions and the structure of extragalactic radio sources." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244791.
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Chandra, Arunchandra. "The turbulent structure of the clear and cloud-topped convective boundary layer over land." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114422.
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Over land, the daytime evolution of the convective boundary layer (CBL) is driven by the strong surface forcing evolution. Recent modeling studies have demonstrated that models cannot capture the observed evolution because of difficulty to represent turbulent processes in CBL and shallow cumulus clouds. The purpose of this thesis is to advance our understanding of the structure of clear and cloudy boundary layer over land by providing observational evidence using long-term dataset. Specifically, it focuses on documenting the turbulent structure and properties of CBL and FWC using observations at the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Climate Research Facility. First, Doppler velocity measurements from insects occupying the lowest 2 km of the boundary layer during summer months are used to map the vertical velocity component in the CBL. The observations cover four summer periods (2004–08) and are classified into cloudy and clear boundary layer conditions. A conditional sampling method is applied to the original Doppler velocity data set to extract coherent vertical velocity structures and to examine plume dimension and its contribution to the total turbulent transport. Profiles of vertical velocity variance, skewness, and mass flux are estimated to study the daytime evolution of the convective boundary layer during these conditions. The properties of summer time FWC clouds are analyzed using the long data record (14–year) of ground-based MMCR (Millimeter Wavelength Cloud Radar) observations at the ARM facility at the SGP site to document the macroscopic and dynamical properties of FWC clouds. Doppler velocities are processed for lower reflectivity thresholds that contain small cloud droplets having insignificant terminal velocities; thus Doppler velocities used as tracers of air motion. A fuzzy-logic based algorithmis developed to eliminate insect radar echoes in the boundary layer that hinder our ability to develop representative cloud statistics. The refined data set is used to document composite daytime evolution of cloud vertical velocity statistics, surface parameters and profiles of updraft and downdraft fractions, updraft and downdraft velocity, and updraft mass fluxes. Statistics on the cloud geometrical properties such as, cloud thickness, cloud chord length, cloud spacing and aspect ratios are calculated on the cloud scale. Lastly, some of the updraft aspects in existing mass-flux parameterizations are tested using the recent observations from Doppler lidar deployed since Midlatitude Continental Convective Cloud Experiment (MC3E). The updraft aspects from two existing mass-flux schemes are evaluated with the Doppler lidar vertical velocity observations to test its applicability over land. The vertical velocity observations in the subcloud layer are analyzed for various cloud conditions by separately decomposing into clear and cloudy regions, and for various cloud fractions to investigate the role of clouds on the subcloud structure.<br>Sur les continents, l'évolution diurne de la couche limite convective (CLC) est entrainée par l'évolution des forçages de surface. Les modélisations récentes ont démontré que les modèles ne peuvent pas capturer l'évolution observée en raison des difficultés pour représenter les processus turbulents dans les nuages cumulus de la CLC et peu profonde. Le but de cette thèse est de faire progresser notre compréhension de la structure de la couche limite claire et nuageuse sur les terres en fournissant des données d'observation à long terme et en utilisant un ensemble de données. Plus précisément, elle met l'accent sur la documentation de la structure turbulente et les propriétés de la CLC et des cumulus de beau temps (CBT) à l'aide d'observation acquise au site de recherches « Southern Great Plains » (SGP) du programme « Atmospheric Radiation Measurement » (ARM) du Département américain de l'énergie. Premièrement, les mesures de vitesse Doppler des insectes, qui occupent les 2 km au bas de la couche limite pendant les mois d'été, sont utilisés pour cartographier la composante de vitesse verticale dans la CLC. Les observations portent sur quatre périodes estivales (2004 - 08) et sont classées en conditions de couche limite claire et nuageuse. Un procédé d'échantillonnage conditionnel est appliqué aux données d'origine de vitesse Doppler pour extraire les structures cohérentes de vitesse verticale et pour examiner la dimension du panache et sa contribution au transport turbulent total. Les profils de la variance et de l'asymétrie de la vitesse verticale et du flux de masse sont estimés pour étudier l'évolution diurne de la CLC au cours de ces conditions. Les propriétés des nuages CBT d'été sont analysées en utilisant le long jeu de données d'observations (14 années) à partir du sol de MMCR (Radar de nuages à longueur d'onde millimétrique) au laboratoire SGP de ARM afin de documenter les propriétés macroscopiques et dynamiques des nuages CBT. Les vitesses Doppler sont traitées pour des seuils inférieurs de réflectivité qui contiennent de petites gouttelettes de nuages ayant des vitesses terminales négligeables; ainsi les vitesses Doppler sont utilisées comme des traceurs de mouvements de l'air. Un algorithme de logique floue a été développé pour éliminer les échos radar d'insectes dans la couche limite qui entravent notre capacité d'élaborer des statistiques représentatives des nuages. L'ensemble de données raffineés est utilisé pour documenter l'évolution diurne compose des statistiques de vitesse verticale des nuages, les paramètres de surface et des profils des fractions de courant ascendant et descendant, la vitesse des courants ascendant et descendants, et les flux de masse ascendant. Les statistiques sur les propriétés géométriques des nuages telles que, l'épaisseur des nuages, la longueur de corde des nuages, l'espacement des nuages et les rapports d'aspect sont calculés sur l'échelle nuageuse. Enfin, quelques uns des aspects des courants ascendants dans les paramétrisations existantes du flux de masse sont testées en utilisant les observations récentes du lidar Doppler déployé depuis l'expérience « Midlatitude Continental Convective Cloud Experiment » (MC3E). Les caractéristiques des courants ascendants de deux schéma existants de flux de masse sont évalués avec les observations de vitesse verticale du lidar Doppler pour tester son applicabilité sur les terres. Les observations de vitesse verticale dans la couche sous les nuages sont analysées pour différentes conditions nuageuses, en décomposant séparément les régions claires et nuageuses, et pour différentes fractions de nuages pour étudier le rôle des nuages sur la structure sous-nuageuse.
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Shetty, Rahul. "Gas kinematics and dynamics [electronic resource: spiral structure and cloud formation in disk galaxies /." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7603.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Dept. of Astronomy. 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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Swetnam, Tyson L., Jeffrey K. Gillan, Temuulen T. Sankey, et al. "Considerations for Achieving Cross-Platform Point Cloud Data Fusion across Different Dryland Ecosystem Structural States." FRONTIERS MEDIA SA, 2018. http://hdl.handle.net/10150/626554.
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Remotely sensing recent growth, herbivory, or disturbance of herbaceous and woody vegetation in dryland ecosystems requires high spatial resolution and multi-temporal depth. Three dimensional (3D) remote sensing technologies like lidar, and techniques like structure from motion (SfM) photogrammetry, each have strengths and weaknesses at detecting vegetation volume and extent, given the instrument's ground sample distance and ease of acquisition. Yet, a combination of platforms and techniques might provide solutions that overcome the weakness of a single platform. To explore the potential for combining platforms, we compared detection bias amongst two 3D remote sensing techniques (lidar and SfM) using three different platforms [ground-based, small unmanned aerial systems (sUAS), and manned aircraft]. We found aerial lidar to be more accurate for characterizing the bare earth (ground) in dense herbaceous vegetation than either terrestrial lidar or aerial SfM photogrammetry. Conversely, the manned aerial lidar did not detect grass and fine woody vegetation while the terrestrial lidar and high resolution near-distance (ground and sUAS) SfM photogrammetry detected these and were accurate. UAS SfM photogrammetry at lower spatial resolution under-estimated maximum heights in grass and shrubs. UAS and handheld SfM photogrammetry in near-distance high resolution collections had similar accuracy to terrestrial lidar for vegetation, but difficulty at measuring bare earth elevation beneath dense herbaceous cover. Combining point cloud data and derivatives (i.e., meshes and rasters) from two or more platforms allowed for more accurate measurement of herbaceous and woody vegetation (height and canopy cover) than any single technique alone. Availability and costs of manned aircraft lidar collection preclude high frequency repeatability but this is less limiting for terrestrial lidar, sUAS and handheld SfM. The post-processing of SfM photogrammetry data became the limiting factor at larger spatial scale and temporal repetition. Despite the utility of sUAS and handheld SfM for monitoring vegetation phenology and structure, their spatial extents are small relative to manned aircraft.
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Gardiner, Lance T. "The 3D structure and stellar content of the outer parts of the Small Magellanic Cloud." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/28085.
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This study is directed towards investigating the structure and stellar content of the Small Magellanic Cloud (SMC), the second nearest external galaxy, with the aim of understanding its evolutionary development in the context of its interactions with the Large Magellanic Cloud and our own Galaxy. The study extends the work done by D Hatzidimitriou on the north-eastern and south-western parts of the SMC, which was presented in her PhD thesis (1988), to cover the rest of the outer area lying beyond about 2 kpc from the SMC centre. Including the plate material utilised by D Hatzidimitriou, the observational material for this project consists of 38 good quality blue and red photographic plates taken with the UK Schmidt Telescope in Australia. The plates were digitised by the COSMOS automatic measuring machine and calibrated by CCD sequences obtained at the Danish 1.5-m telescope at ESO in Chile. The resulting database consists of positional and colour-magnitude data for 1.1 million objects covering nearly the whole of the outer area of the SMC. The scientific analysis involved the study of the properties of colour-magnitude diagrams in conjunction with surface distribution plots of different stellar populations in order to derive the detailed positional dependence of the line-of-sight depth and the past star formation history of the outer parts of the SMC. This has led to confirmation that the depth of the SMC exceeds its tidal radius in the eastern projected areas and supports current ideas suggesting the disintegration of the SMC. Supplementary CCD observations of the south-eastern outlying SMC cluster NGC 643 and the surrounding field region, obtained at the South African Astronomical Observatory 1-m telescope, are reported. A wide area search for RR-Lyrae candidates using the available plate material was also conducted which yielded 95 candidates in the northern outer parts of the SMC. A detailed study of the Wing region of the SMC has also been made.
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Renner, Swen Christoph. "Structure and diversity of cloud forest bird communities in Alta Verapaz, Guatemala, and implications for conservation." Doctoral thesis, [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969959478.
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BJORAKER, GORDON LEE. "THE GAS COMPOSITION AND VERTICAL CLOUD STRUCTURE OF JUPITER'S TROPOSPHERE DERIVED FROM FIVE MICRON SPECTROSCOPIC OBSERVATIONS." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187942.
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Spectroscopic observations of Jupiter at 5 microns were analyzed in order to derive the gas composition and vertical cloud structure for the 2 to 6 bar portion of the Jovian troposphere. Two infrared data sets were used. The first one consisted of high spectral resolution observations of Jupiter between -40 and +40 latitude acquired from the Kuiper Airborne Observatory. The second data set consisted of high spatial resolution measurements of Jupiter's belts and zones using the Voyager 1 Infrared Interferometer Spectrometer and Radiometer (IRIS). A spectrum synthesis program was used to calculate the emergent radiance from Jupiter's atmosphere between 1800 and 2250 cm⁻¹. The temperature-pressure profile and spectroscopic line parameters for seven molecules were specified. Gas mole fractions were adjusted until the calculated spectrum agreed with the observations within error limits. Molecular hydrogen is an important absorber at 5 microns. Absorption coefficients were generated as functions of frequency and temperature. Unit optical depth at 5 microns due to H₂ takes place between 5 and 7 bars in Jupiter's atmosphere. The airborne spectrum was used to infer the mole fractions of NH₃, PH₃, CH₄, CH₃D, CO, GeH₄, and H₂O for the 2 to 6 bar portion of Jupiter's troposphere. Elemental ratios were calculated and compared with model predictions. The N/H ratio is 1.5 ± 0.2 times the Lambert (1978) values for the Sun. The P/H ratio is 1.0 ± 0.1 times the Anders and Ebihara (1982) meteoritic value. The C/H ratio is 3.6 ± 0.7 times solar. The D/H ratio is 1.2 x 10⁻⁵. The mole fractions of CO and GeH₄ are (1.0 ± 0.3) x 10⁻⁹ and (7.0 ± 4) x 10⁻¹⁰, respectively. The mole fraction of H₂O was found to be the same in Jupiter's belts and zones, except for a factor of 2 depletion in the North Equatorial Belt Hot Spots. The H₂O mole fraction for the 2 to 4 bar region is (4.0 ± 1.0) x 10⁻⁶. This value increases with depth to (3.0 ± 2.0) x 10⁻⁵ at 6 bars. The H₂O ice cloud would be located near 2 bars. The O/H ratio at P = 6 bars is depleted by a factor of 40 with respect to the Sun. The thermal emission signature at 5 microns of optically thick clouds was used to develop a one-dimensional cloud model for Jupiter. The belt-to-zone variation in 5 micron flux is attributed to a massive cloud layer at 2 bars, T = 200 K, composed of NH₄SH and H₂O ice. A lower cloud at 5 bars is inconsistent with the IRIS data. Continuum absorption by H₂ determines the penetration depth at 5 microns, not a lower cloud layer.
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Laporte, Chervin F. P., Facundo A. Gómez, Gurtina Besla, Kathryn V. Johnston, and Nicolas Garavito-Camargo. "Response of the Milky Way's disc to the Large Magellanic Cloud in a first infall scenario." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/626276.
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We present N-body and hydrodynamical simulations of the response of the Milky Way's baryonic disc to the presence of the Large Magellanic Cloud during a first infall scenario. For a fiducial Galactic model reproducing the gross properties of the Galaxy, we explore a set of six initial conditions for the Large Magellanic Cloud (LMC) of varying mass which all evolve to fit the measured constraints on its current position and velocity with respect to the Galactic Centre. We find that the LMC can produce strong disturbances - warping of the stellar and gaseous discs - in the Galaxy, without violating constraints from the phase-space distribution of stars in the Solar Neighbourhood. All models correctly reproduce the phases of the warp and its antisymmetrical shape about the disc's mid-plane. If the warp is due to the LMC alone, then the largest mass model is favoured (2.5 x 10(11) M-circle dot). Still, some quantitative discrepancies remain, including deficits in height of Delta Z = 0.7 kpc at R = 22 kpc and Delta Z = 0.7 kpc at R = 16 kpc. This suggests that even higher infall masses for the LMC's halo are allowed by the data. A comparison with the vertical perturbations induced by a heavy Sagittarius dSph model (10(11) M-circle dot) suggest that positive interference with the LMC warp is expected at R = 16 kpc. We conclude that the vertical structure of the Galactic disc beyond the Solar Neighbourhood may jointly be shaped by its most massive satellites. As such, the current structure of the Milky Way suggests we are seeing the process of disc heating by satellite interactions in action.
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Carlhoff, Philipp Christoph [Verfasser], Peter [Akademischer Betreuer] Schilke, and Jürgen [Akademischer Betreuer] Stutzki. "Molecular cloud structure in the star-forming region W43 / Philipp Christoph Carlhoff. Gutachter: Peter Schilke ; Jürgen Stutzki." Köln : Universitäts- und Stadtbibliothek Köln, 2014. http://d-nb.info/1048676994/34.
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Eriksson, Simon. "A Photometric Variability Study Using Brown Dwarfs As Giant Planet Analogues : Investigating rotation periods and cloud structure." Thesis, Stockholms universitet, Institutionen för astronomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-152174.
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Sotiropoulou, Georgia. "The Arctic Atmosphere : Interactions between clouds, boundary-layer turbulence and large-scale circulation." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-134525.
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Arctic climate is changing fast, but weather forecast and climate models have serious deficiencies in representing the Arctic atmosphere, because of the special conditions that occur in this region. The cold ice surface and the advection of warm air aloft from the south result in a semi-continuous presence of a temperature inversion, known as the “Arctic inversion”, which is governed by interacting large-scale and local processes, such as surface fluxes and cloud formation. In this thesis these poorly understood interactions are investigated using observations from field campaigns on the Swedish icebreaker Oden: The Arctic Summer Cloud Ocean Study (ASCOS) in 2008 and the Arctic Clouds in Summer Experiment (ACSE) in 2014. Two numerical models are also used to explore these data: the IFS global weather forecast model from the European Center for Medium-range Weather Forecasts and the MIMICA LES from Stockholm University. Arctic clouds can persist for a long time, days to weeks, and are usually mixed-phase; a difficult to model mixture of super-cooled cloud droplets and ice crystals. Their persistence has been attributed to several mechanisms, such as large-scale advection, surface evaporation and microphysical processes. ASCOS observations indicate that these clouds are most frequently decoupled from the surface; hence, surface evaporation plays a minor role. The determining factor for cloud-surface decoupling is the altitude of the clouds. Turbulent mixing is generated in the cloud layer, forced by cloud-top radiative cooling, but with a high cloud this cannot penetrate down to the surface mixed layer, which is forced primarily by mechanical turbulence. A special category of clouds is also found: optically thin liquid-only clouds with stable stratification, hence insignificant in-cloud mixing, which occur in low-aerosol conditions. IFS model fails to reproduce the cloud-surface decoupling observed during ASCOS. A new prognostic cloud physics scheme in IFS improves simulation of mixed-phase clouds, but does not improve the warm bias in the model, mostly because IFS fails to disperse low surface-warming clouds when observations indicate cloud-free conditions. With increasing summer open-water areas in a warming Arctic, there is a growing interest in processes related to the ice marginal zones and the summer-to-autumn seasonal transition. ACSE included measurements over both open-water and sea-ice surfaces, during melt and early freeze. The seasonal transition was abrupt, not gradual as would have been expected if it was primarily driven by the gradual changes in net solar radiation. After the transition, the ocean surface remained warmer than the atmosphere, enhancing surface cooling and facilitating sea-ice formation. Observations in melt season showed distinct differences in atmospheric structure between the two surface types; during freeze-up these largely disappear. In summer, large-scale advection of warm and moist air over melting sea ice had large impacts on atmospheric stability and the surface. This is explored with an LES; results indicate that while vertical structure of the lowest atmosphere is primarily sensitive to heat advection, cloud formation, which is of great importance to the surface energy budget, is primarily sensitive to moisture advection.<br><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>
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Jiang, Hanqiu. "Structure, dynamic, and thermodynamic relationships of worm-like micelles." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1553618133295199.
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Stonell, G. P. "The track structure of protons and other radiations in pure water vapour measured in a low pressure cloud chamber." Thesis, University of Westminster, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373002.
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Risbey, James S. (James Sydney). "An analysis of zonal mean atmospheric angular momentum and high cloud cover : periodicities, time-latitude structure, and cross correlations." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/57727.
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Espling, Daniel. "Enabling Technologies for Management of Distributed Computing Infrastructures." Doctoral thesis, Umeå universitet, Institutionen för datavetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-80129.
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Computing infrastructures offer remote access to computing power that can be employed, e.g., to solve complex mathematical problems or to host computational services that need to be online and accessible at all times. From the perspective of the infrastructure provider, large amounts of distributed and often heterogeneous computer resources need to be united into a coherent platform that is then made accessible to and usable by potential users. Grid computing and cloud computing are two paradigms that can be used to form such unified computational infrastructures. Resources from several independent infrastructure providers can be joined to form large-scale decentralized infrastructures. The primary advantage of doing this is that it increases the scale of the available resources, making it possible to address more complex problems or to run a greater number of services on the infrastructures. In addition, there are advantages in terms of factors such as fault-tolerance and geographical dispersion. Such multi-domain infrastructures require sophisticated management processes to mitigate the complications of executing computations and services across resources from different administrative domains. This thesis contributes to the development of management processes for distributed infrastructures that are designed to support multi-domain environments. It describes investigations into how fundamental management processes such as scheduling and accounting are affected by the barriers imposed by multi-domain deployments, which include technical heterogeneity, decentralized and (domain-wise) self-centric decision making, and a lack of information on the state and availability of remote resources. Four enabling technologies or approaches are explored and developed within this work: (I) The use of explicit definitions of cloud service structure as inputs for placement and management processes to ensure that the resulting placements respect the internal relationships between different service components and any relevant constraints. (II) Technology for the runtime adaptation of Virtual Machines to enable the automatic adaptation of cloud service contexts in response to changes in their environment caused by, e.g., service migration across domains. (III) Systems for managing meta-data relating to resource usage in multi-domain grid computing and cloud computing infrastructures. (IV) A global fairshare prioritization mechanism that enables computational jobs to be consistently prioritized across a federation of several decentralized grid installations. Each of these technologies will facilitate the emergence of decentralized computational infrastructures capable of utilizing resources from diverse infrastructure providers in an automatic and seamless manner.<br><p>Note that the author changed surname from Henriksson to Espling in 2011</p>
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Pérault, Michel. "Structure et evolution des nuages moleculaires." Paris 7, 1987. http://www.theses.fr/1987PA077145.
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Description et comprehension des systemes gazeux lies par leur propre gravite grace a l'etude detaillee de quelques nuages moleculaires proches du soleil, et a l'aide de l'analyse plus globale du rayonnement des molecules et des particules solides de l'ensemble du disque galactique. Etude theorique des ecoulements hydrodynamiques siegeant dans ces nuages moleculaires pour tenter d'apprehender le taux de formation stellaire et la fonction initiale de masse calcules d'apres des observations faites
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Espling, Daniel. "Metadata Management in Multi-Grids and Multi-Clouds." Licentiate thesis, Umeå universitet, Institutionen för datavetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-51159.
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Grid computing and cloud computing are two related paradigms used to access and use vast amounts of computational resources. The resources are often owned and managed by a third party, relieving the users from the costs and burdens of acquiring and managing a considerably large infrastructure themselves. Commonly, the resources are either contributed by different stakeholders participating in shared projects (grids), or owned and managed by a single entity and made available to its users with charging based on actual resource consumption (clouds). Individual grid or cloud sites can form collaborations with other sites, giving each site access to more resources that can be used to execute tasks submitted by users. There are several different models of collaborations between sites, each suitable for different scenarios and each posing additional requirements on the underlying technologies. Metadata concerning the status and resource consumption of tasks are created during the execution of the task on the infrastructure. This metadata is used as the primary input in many core management processes, e.g., as a base for accounting and billing, as input when prioritizing and placing incoming task, and as a base for managing the amount of resources allocated to different tasks. Focusing on management and utilization of metadata, this thesis contributes to a better understanding of the requirements and challenges imposed by different collaboration models in both grids and clouds. The underlying design criteria and resulting architectures of several software systems are presented in detail. Each system addresses different challenges imposed by cross-site grid and cloud architectures: The LUTSfed approach provides a lean and optional mechanism for filtering and management of usage data between grid or cloud sites. An accounting and billing system natively designed to support cross-site clouds demonstrates usage data management despite unknown placement and dynamic task resource allocation. The FSGrid system enables fairshare job prioritization across different grid sites, mitigating the problems of heterogeneous scheduling software and local management policies. The results and experiences from these systems are both theoretical and practical, as full scale implementations of each system has been developed and analyzed as a part of this work. Early theoretical work on structure-based service management forms a foundation for future work on structured-aware service placement in cross- site clouds.
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Bose, Saptak. "An integrated approach encompassing point cloud manipulation and 3D modeling for HBIM establishment: a case of study." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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In the case of Cultural Heritage buildings, the need for an effective, exhaustive, efficient method to replicate its state of being in an interactive, three-dimensional environment is today, of paramount importance, both from an engineering as well as a historical point of view. Modern geomatics entails the usage of Terrestrial Laser Scanners (TLS) and photogrammetric modelling from Structure-from-Motion (SfM) techniques to initiate this modelling operation. To realize its eventual existence, the novel Historic Building Information Modelling (HBIM) technique is implemented. A prototype library of parametric objects, based on historic architectural data, HBIM allows the generation of an all-encompassing, three-dimensional model which possesses an extensive array of information pertaining to the structure at hand. This information, be it geometric, architectural, or even structural, can then be used to realize reinforcement requirements, rehabilitation needs, stage of depreciation, method of initial construction, material makeup, historic alterations, etc. In this paper, the study of the San Michele in Acerboli’s church, located in Santarcangelo di Romagna, Italy, is considered. A HBIM model is prepared and its accuracy analyzed. The final model serves as an information repository for the aforementioned Church, able to geometrically define its finest characteristics.
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Blanchard, Laurine. "Impact of lightning on evolution, structure and function of bacterial communities." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-01024190.
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To diversify their genetic material, allowing adaptation to environmental disturbances and colonization of new ecological niches, bacteria use various evolutionary processes, including the acquisition of new genetic material by horizontal transfer mechanisms such as conjugation, transduction and transformation. Electrotransformation mediated by lightningrelated electrical phenomena may constitute an additional gene transfer mechanism occurring in nature. The presence in clouds of bacteria capable of forming ice nuclei that lead to precipitations and are involved in the triggering of lightning, such as the global phytopathogen Pseudomonas syringae, led us to postulate that natural electrotransformation in clouds may affect bacteria, by contributing to increase their adaptive potential. We first determined if the ice nucleator bacterium P. syringae could survive when in clouds and acquire exogenous genetic material through lightning shock-simulating in vitro electroporation. In comparison to two other bacteria, P. syringae appears to be best adapted for survival and for genetic electrotransformation under these conditions, which suggests that this bacterium would be able to survive and evolve whilst being transported in clouds. Secondly, we evaluated the impact of lightning shock-simulating in vitro electroporation on the survival, the electrotransformation potential and the diversity of bacteria collected from rain samples. These isolates better resisted lightning than the laboratory strains and some were able to electrotransform exogenous DNA. The rain bacteria we isolated were of different origins and were representative of life modes of the various sources of bacterial emissions on Earth. Our study suggests that bacteria aerosolized from diverse terrestrial ecosystems can spread to new habitats through clouds whilst also being able to acquire new genetic material via lightning-based electrotransformation, thereby potentially enhancing their genetic diversity. The final part of our work consisted of evaluating whether electrotransformation could be applied to the engineering of indigenous soil bacteria in order to develop a tool for the bioremediation of lindane, a once widely used pesticide. Optimized experiments revealed that both natural and electrotransformation contributed to the incorporation of a plasmid harboring a gene encoding the first lindane dechlorination steps by indigenous soil bacteria. In conclusion, we showed that natural electrotransformation mediated by electrical discharges such as those occurring in clouds or reaching soils can be involved in the horizontal gene transfer process among bacteria and, considering the importance of lightning worldwide, may play a role in the adaptation and evolution of these organisms.
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Casoli, Fabienne. "Nuages moléculaires, formation d'étoiles et structure spirale." Paris 7, 1987. http://www.theses.fr/1987PA077099.
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Résultats d'observation millimétriques de **(12)CO et **(13)CO, utilisés comme traceurs des nuages moléculaires. Etude de leur structure en fonction de la présence d'une barre, de bras spiraux ou d'une interaction. Présentation de quelques cas plus ou moins actifs
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Zhang, Guangjian. "Etude expérimentale de la structure et de la dynamique des écoulements cavitants." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE050.
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La cavitation est un phénomène complexe impliquant un transfert de masse entre la phase liquide et vapeur à des températures presque constantes.Les processus physiques qui contrôlent les instabilités dans les écoulements cavitants ne sont pas encore compris, principalement en raison du manque de données expérimentales quantitatives sur les structures diphasiques et la dynamique à l'intérieur des zones de cavitation opaques. Dans cette thèse, la cavitation partielle développée dans de petits canaux convergents-divergents (Venturi) a été étudiée expérimentalement en détail pour élucider ces mécanismes. Ceci a été réalisé en combinant une technique d'imagerie par rayons X ultra-rapide, la visualisation conventionnelle à haute fréquence et la vélocimétrie par images de particules. Les principales contributions de la présente étude portent sur les quatre aspects suivants:(1) une description détaillée des structures d'écoulement diphasique au sein des poches de cavitation quasi stables,qui se caractérisent par un écoulement rentrant à faible vitesse existant en continu sous la cavité; (2) analyse de l'effet complexe de la cavitation sur les fluctuations de vitesses turbulentes; (3) identification et discussion de trois mécanismes distincts responsables de la transition vers un comportement instable périodique ; (4) analyse de l'effet d'échelle sur les comportements cavitants, dans le cas des profils Venturi étudiés<br>Cavitation is a complex phenomenon involving mass transfer between liquid and vapour phase at nearly constanttemperature. Advances in the understanding of the physical processes of cavitating flows are challenging, mainlydue to the lack of quantitative experimental data on the two-phase structures and dynamics inside the opaquecavitation areas. In this thesis, partial cavitation developed in small convergent-divergent (Venturi) channels wasstudied experimentally in detail for a better knowledge of the physical mechanisms governing the cavitationinstabilities. This was achieved by using an ultra-fast synchrotron X-ray imaging technique aided withconventional high speed photography and Particle Image Velocimetry. The main contributions of the presentstudy can be summarized as follows: (1) detailed description of the two-phase flow structures in quasi-stablesheet cavitation, which is characterized by a low-speed re-entrant flow existing continuously underneath thecavity; (2) analysis of the complex effect of cavitation on turbulent velocity fluctuations; (3) identification ofthree distinct mechanisms responsible for the transition of sheet-to-cloud cavitation, with a discussion of thedifferences between them; (4) analysis of the scale effect on cavitation in the studied Venturi flows
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Otepka, Johannes, Sajid Ghuffar, Christoph Waldhauser, Ronald Hochreiter, and Norbert Pfeifer. "Georeferenced Point Clouds: A Survey of Features and Point Cloud Management." MDPI AG, 2013. http://dx.doi.org/10.3390/ijgi2041038.
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This paper presents a survey of georeferenced point clouds. Concentration is, on the one hand, put on features, which originate in the measurement process themselves, and features derived by processing the point cloud. On the other hand, approaches for the processing of georeferenced point clouds are reviewed. This includes the data structures, but also spatial processing concepts. We suggest a categorization of features into levels that reflect the amount of processing. Point clouds are found across many disciplines, which is reflected in the versatility of the literature suggesting specific features. (authors' abstract)
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Thomas, Anita. "Classification of Man-made Urban Structures from Lidar Point Clouds with Applications to Extrusion-based 3-D City Models." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429484410.
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Fallqvist, Marcus. "Automatic Volume Estimation Using Structure-from-Motion Fused with a Cellphone's Inertial Sensors." Thesis, Linköpings universitet, Datorseende, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-144194.
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The thesis work evaluates a method to estimate the volume of stone and gravelpiles using only a cellphone to collect video and sensor data from the gyroscopesand accelerometers. The project is commissioned by Escenda Engineering withthe motivation to replace more complex and resource demanding systems with acheaper and easy to use handheld device. The implementation features popularcomputer vision methods such as KLT-tracking, Structure-from-Motion, SpaceCarving together with some Sensor Fusion. The results imply that it is possible toestimate volumes up to a certain accuracy which is limited by the sensor qualityand with a bias.<br>I rapporten framgår hur volymen av storskaliga objekt, nämligen grus-och stenhögar,kan bestämmas i utomhusmiljö med hjälp av en mobiltelefons kamerasamt interna sensorer som gyroskop och accelerometer. Projektet är beställt avEscenda Engineering med motivering att ersätta mer komplexa och resurskrävandesystem med ett enkelt handhållet instrument. Implementationen använderbland annat de vanligt förekommande datorseendemetoderna Kanade-Lucas-Tommasi-punktspårning, Struktur-från-rörelse och 3D-karvning tillsammans medenklare sensorfusion. I rapporten framgår att volymestimering är möjligt mennoggrannheten begränsas av sensorkvalitet och en bias.
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Jacq, Thierry. "Le survey radiomillimetrique de l'observatoire de bordeaux : le gaz moleculaire interstellaire dans le plan galactique entre l=38 et l=67.5, structure spirale, nuages moleculaires, comparaison entre hi et **(13)co. ch dans le nuage sombre lynds 134." Paris 6, 1987. http://www.theses.fr/1987PA066440.
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L'observation radiomillimetrique a 110. 2 ghz du plan galactique a permis d'identifier 181 nuages interstellaires dont certains parametres sont listes. Deux bras spiraux sont mis en evidence: celui de persee d'inclinaison 12**(o) et un bras mineur lie au gaz local et incline de 22**(o). Les donnees moleculaires sont correlees aux donnees hi obtenues a arecibo et les resultats de cette comparaison sont presentes. D'autre part le nuage sombre l 134 est observe a 9 cm en ch et l'abondance relative de ce radical en fonction de la position est determinee
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Nguyen, Anh-Dung. "Contributions to modeling, structural analysis, and routing performance in dynamic networks." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/9725/1/nguyen.pdf.
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This thesis contributes to the modeling, understanding and efficient communication in dynamic networks populating the periphery of the Internet. By dynamic networks, we refer to networks that can be modeled by dynamic graphs in which nodes and links change temporally. In the first part of the thesis, we propose a new mobility model - STEPS - which captures a wide spectrum of human mobility behavior. STEPS implements two fundamental principles of human mobility: preferential attachment and attractor. We show that this simple parametric model is able to capture the salient statistical properties of human mobility such as the distribution of inter-contact/contact time. In the second part, using STEPS, we analyze the fundamental behavioral and structural properties of opportunistic networks. We redefine in the context of dynamic networks the concept of small world structure and show how such a structure can emerge. In particular, we show that highly dynamic nodes can play the role of bridges between disconnected components, helping to significantly reduce the length of network path and contribute to the emergence of small-world phenomenon in dynamic networks. We propose a way to model this phenomenon in STEPS. From a regular dynamic network in which nodes limit their mobility to their respective preferential areas. We rewire this network by gradually injecting highly nomadic nodes moving between different areas. We show that when the ratio of such nomadic nodes is around 10%, the network has small world structure with a high degree of clustering and a low characteristic path length. The third contribution of this thesis is the study of the impact of disorder and contact irregularity on the communication capacity of a dynamic network. We analyze the degree of disorder of real opportunistic networks and show that if used correctly, it can significantly improve routing performances. We then introduce a model to capture the degree of disorder in a dynamic network. We propose two simple and efficient algorithms that exploit the temporal structure of a dynamic network to deliver messages with a good tradeoff between resource usage and performance. The simulation and analytical results show that this type of algorithm is more efficient than conventional approaches. We also highlight also the network structure for which this type of algorithm achieves its optimum performance. Based on this theoretical result, we propose a new efficient routing protocol for content centric opportunistic networks. In this protocol, nodes maintain, through their opportunistic contacts, an utility function that summarizes their spatio-temporal proximity to other nodes. As a result, routing in this context consists in following the steepest slopes of the gradient field leading to the destination node. This property leads to a simple and effective algorithm routing that can be used both in the context of IP networks and content centric networks. The simulation results show that this protocol outperforms traditional routing protocols already defined for opportunistic networks. The last contribution of this thesis is to highlight the potential application of dynamic networks in the context of "mobile cloud computing." Using the particle optimization techniques, we show that mobility can significantly increase the processing capacity of dynamic networks. In addition, we show that the dynamic structure of the network has a strong impact on its processing capacity.
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Di, Biase Tonya. "Riconoscimento della forma e posa di un oggetto 3D tramite algoritmi di Structure from Motion per applicazioni robotiche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Il lavoro esposto nel seguente elaborato di tesi tratta della ricostruzione tridimensionale di un oggetto, nella sua forma e posa, partendo da immagini 2D che lo ritraggono da diverse prospettive. La ricostruzione ha come fine l'operazione di pick and place dell'oggetto analizzato, utilizzando un robot seriale.
Le immagini sono acquisite utilizzando una videocamera IP collegata al PC tramite connessione IP/TCP. La videocamera è movimentata dal robot collaborativo UR5 dell'Universal Robots; la camera è infatti rigidamente collegata al suo end-effector tramite un apposito supporto progettato e realizzato in laboratorio con stampa 3D.
Per ricostruire la forma dell'oggetto si utilizzano algoritmi di visione artificiale che rientrano nella categoria di Structure from Motion (SfM). Vengono applicati due differenti approcci appartenenti all'SfM, in seguito confrontati.
La posa dell'oggetto nello spazio è ottenuta utilizzando le pose assunte dalla videocamera durante l'acquisizione, espresse rispetto al riferimento della base del robot, e la posizione della camera nel sistema di riferimento dell'end-effector. Quest'ultima si ottiene effettuando la calibrazione eye-on-hand e rimane invariata durante il movimento del robot per via del collegamento rigido presente.
Per valutare la bontà dei risultati ottenuti, è stato necessario definire una nuova metrica di valutazione adatta alle nuvole di punti tridimensionali ottenute. Dalle ricerche effettuate in letteratura, sono stati trovati infatti solo metodi idonei a ricostruzioni bidimensionali.
La metrica sviluppata ha permesso di identificare la migliore tra le metodologie analizzate. L'algoritmo scelto è stato poi applicato in laboratorio per eseguire l'operazione di pick and place dell'oggetto.
In funzione dell'oggetto da ricostruire e afferrare sono state realizzate in stampa 3D due griffe idonee al compito, montate sul gripper del robot.
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Rowles, Jonathan Henry. "The structure of molecular clouds." Thesis, University of Kent, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544095.
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Chen, Anqi. "Structural response to vapour cloud explosions." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23922.
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Over the last few decades, a number of major industrial blast accidents involving oil and gas installations occurred worldwide. These include the blast explosion that occurred in an industrial facility at Buncefield in the United Kingdom in 2005. Extensive damage occurred due to the blast, both to the industrial plant and surrounding buildings, as a consequence of much higher overpressures than would normally be expected from a vapour cloud explosion of this nature. In response to this event, a great deal of work was carried out on collecting and analysing available evidence from the incident in order to understand the explosion mechanism and estimate the overpressure levels within the gas cloud that formed. Subsequent investigations included the examination of steel switch boxes on the site located within the area covered by the vapour cloud. These boxes suffered varying degrees of damage and could therefore be used as overpressure indicators. A series of tests were commissioned after the event in order to compare the damage of the field boxes with detonation tests on similar boxes. The thesis firstly reports on numerical studies carried out on assessing the damage to steel boxes subjected to both detonation and deflagration scenarios in order to aid the investigation of the explosion. Several modelling approaches are adopted in the numerical studies, including: Pure Lagrangian, Uncoupled Lagrangian-Eulerian and Coupled Lagrangian-Eulerian techniques. The numerical models are validated against data collected from gas detonation experiments on similar steel boxes. It is found that the coupled approach is able to predict the results accurately, although such an approach cannot be used in detailed parametric investigations due to its prohibitive computational demand. The pure Lagrangian approach is therefore used instead, but the overpressure range in the parametric assessments is limited to 4 bar (side-on) as an adequate level of accuracy from this modelling technique cannot be ensured beyond this range. The results are summarised in the form of pressure-impulse diagrams, and typical residual shapes are selected with the aim of aiding forensic investigations of future explosion incidents. The investigation is extended thereafter to the response of a steel-clad portal frame structures located outside the gas cloud and which suffered varying degrees of damage. A typical warehouse building is studied through a pure Lagrangian approach. A non-linear finite element model of a representative sub-structure of the warehouse wall is validated against a full scale test carried out at Imperial College London. A series of pressure-impulse diagrams of the sub-structure is then constructed based on the results of parametric non-linear dynamic assessments using the developed numerical model under various combinations of overpressures and impulses. A new failure criterion based on the total failure of the self-tapping screws is proposed in conjunction with pressure-impulse diagrams. This failure condition provides a more direct assessment of the damage to the side walls of the warehouse. The pressure-impulse diagrams can be used to assess the response of a typical warehouse structure to blast loading, and to provide some guidance on the safe siting in a hazardous environment around oil and storage sites. Simplified approaches based on single degree of freedom representations are also employed, and their results are compared with those from the detailed non-linear finite element models. The findings show that the simplified approaches offer a reasonably reliable and practical tool for predicting the response of the side rails. However, it is illustrated that such idealisations are not suited for assessing the ultimate response of cladding panels, as the side rail-cladding interactions cannot be captured by simplified approaches and necessitate the deployment of detailed numerical procedures.
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Toral, Vázquez Javier. "Identification et modélisation du comportement des structures composites assemblées par couplage." Toulouse, ISAE, 2009. http://www.theses.fr/2009ESAE0020.
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L'optimisation des structures aéronautiques fabriquées en composite a mené EADS-IW à développer une technique d'assemblage par cloutage qui a pour objectif la fabrication à coût réduit de sous ensembles structuraux avec un fort niveau d'intégration. L'objectif de ce travail de thèse est d'étudier le comportement mécanique des assemblages cloutés et de proposer des modélisations associées. Dans le cadre d'une démarche multi-niveau, le comportement des liaisons clou/résine et clou stratifié a d'abord été étudié. Des campagnes expérimentales ont montré l'influence du diamètre du clou et de la profondeur d'enfoncement sur la tenue en arrachement ainsi que des similitudes entre le comportement du clou noyé dans de la résine et implanté dans le stratifié. Une modélisation capable d'estimer la tenue en arrachement d'un clou a été développée. Au niveau éprouvettes technologiques, des éprouvettes cloutées représentatives de structures aéronautiques de type « L » ou « T » ont été testés en sollicitations statiques montrant l'influence des paramètres de conception et les possibles avantages du cloutage. Finalement, des modélisations basées sur les études élémentaires ont permis de simuler le comportement de ces éprouvettes cloutées retrouvé en essai et notamment de prédire leur tenue sous sollicitations différentes validant ainsi la démarche multi-niveau.
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Zalet, Ayman. "Vklass datalagring : En studie om datalagring på ett kostands- och prestandaeffektivt sätt." Thesis, KTH, Data- och elektroteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-181892.
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Studien som utförs i detta examensarbete behandlar ämnet datalagring för applikationen Vklass. Problemet som studeras i detta arbete består i att det varje månad inkommer ett stort antal filer till applikationen som lagras på en server lokalt i Stockholm där regelbun-den säkerhetskopiering görs till en annan server. Den implementerade datalagringslösning-en innebär att servern som lagrar data växer ständigt och utan särskild struktur då filerna lagras i en och samma mapp, vilket i sin tur innebär en mer komplex och mindre överskåd-lig lagring av filerna i lagringsmedierna samtidigt som prestandabegränsningar uppstår vid återläsning av säkerhetskopian. Kunden efterfrågar en lösning som innebär en mer effektiv hantering för alla de filer som lagras i applikationen på ett kostnads- och prestandaeffektivt vis. Lösningen bör även möjliggöra lagring av data med en mer överskådlig och lätthanter-lig struktur. De lösningsmetoder som undersökts i arbetet avser datalagring lokalt samt datalagring i molntjänster från de mest framstående aktörerna. Undersökningen och analysen av de valda lösningsmetoderna visade att datalagring i molntjänster uppfyller kraven som den nya data-lagringslösningen ämnar uppnå till skillnad från datalagring lokalt som visade brister och som därmed inte uppfyllde dessa krav. Slutsatsen i arbetet identifierade Microsoft Azure Storage som den mest lämpliga molnleverantören för datalagring då data lagras på ett pre-standa- och struktureffektivt sätt. Lösningen är även kostnadseffektiv då det dyraste lag-ringsalternativet som Microsoft erbjuder sänker lagringskostnaderna för Vklass med 84 % under de kommande fem åren i jämförelse med aktuell lagringsmetod.<br>The study in this report examines data storage for the application Vklass. The problem that has been studied in this work is that the application receives and stores a big amount of files which are stored on a server locally in Stockholm where back up is made to another server on a regular basis. Today’s implemented solution for data storage endorse that the server that stores the files continues to grow each month without further structure since all the upload files is stored in the same folder which yields a more complex and less lucid storage and management for the data. This yields limitations for the performance of the application when the backup-copy needs to be restored. The owners of the application request a solu-tion that gives a more effective management of the stored data with a cost and performance effective technique. The solution that will be presented in this study should also enable stor-ing data with a more lucid and convenient structure. The studied methods for the solution include storing data locally and data storage in the biggest public cloud services. The investigation and analysis of the chosen methods proved that data storage in cloud services fulfilled the requirements for the identified solution as opposed to the methods for storing data locally that proved to yield deficits which would not fulfill these requirements. The deduction of this study identified Microsoft Azure Sto-rage to be the best public cloud solution for the given problem since data is stored in a per-formance and structure effective way. It was also proven that even the most expensive sto-rage solution provided by Azure Storage lowered the costs for data storage by 84 percent compared to today’s data storage solution during the first five years.
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Duvall, Emily M. "Factors influencing the structures of the Monterey Bay sea breeze." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FDuvall.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, March 2004.<br>Thesis advisor(s): Wendell A. Nuss. Includes bibliographical references (p. 59-60). Also available online.
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Hobson, Michael Paul. "The small-scale structure of molecular clouds." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282113.
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Christie, H. "Structure and depletion in star forming clouds." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1367071/.
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Observations of star forming molecular clouds reveal clumpiness on all scales, both in the spectra of molecules and thermal continuum emission from the solid component of the interstellar medium, the dust. Recent, high resolution maps have allowed us to probe down to extremely small scales at which we see clumps of radii just several hundredths of a parsec. A good knowledge of the structure of these regions, and of the chemical processes occurring within, is crucial if we want to properly understand the early stages of star formation and the resulting stellar population. However, observations of cold, dense environments are challenging. Molecules emit at long wavelengths which are notoriously difficult to observe. A comparison with models is also complicated by the fact that in these conditions molecules will freeze-out onto dust grain surfaces forming icy mantles. We know little about the rate at which this process occurs in interstellar conditions, or the chemical reactions that happen on the grain surfaces. In this thesis we present two alternative methods by which to investigate the underlying clumpy nature of a molecular cloud and consider freeze-out in such an environment. Small, quiescent regions of enhanced emission in several molecules (including ammonia and HCO+) have been observed near to Herbig-Haro objects (HHOs) in star forming clouds. It was suggested that these could be due to molecules in small dense clumps being liberated from the dust grain surface by radiation from the shock front. Chemical modelling later proved this theory to be viable, and it was further supported by observational surveys and more detailed modelling of specific regions. In chapter 2 we simulate a dense clump near to an HHO, adapting the chemical code used in the original models to allow the shock front to move past the clump, providing a more realistic description of the effect of the radiation field. Chapter 3 describes how the outputs from these models can be used to simulate observations of part of a molecular cloud made up of small, transient density enhancements irradiated by a passing shock front. We briefly compare our synthetic maps with HCO+ spectra in regions surrounding HHOs. Commonly, researchers use decomposition algorithms on 2D and 3D maps to pick out clumps of emission and evaluate their properties. The mass functions of these objects often appear to emulate the stellar initial mass function, which has led researchers to conclude that the stellar mass is set at a very early stage, prior to the switch on of the protostar. In Chapter 4 we introduce the Gould Belt clouds for which we have HARP CO and SCUBA data (the HARP maps are presented in Appendix B). It is these on which we perform the analysis described in the final 3 Chapters. In Chapter 5 we investigate four popular clumpfinding algorithms, testing them on both synthetic and real (HARP) data, and explore the impact of user defined input parameters on derived properties. We choose one algorithm, with one set of input parameters, and use this to analyse the distribution of CO clumps in five nearby molecular clouds. The results of this study are outlined in Chapter 6. Chapter 7 focuses on the process by which CO freezes-out (depletes) onto the surfaces of dust grains in dark clouds. A single value for the depletion of a particular molecule is difficult to achieve because of its strong dependence on environmental factors and the past evolution of a region. However, we have a consistent data set across a range of environments and so are able to perform a statistical study in which we compare hydrogen densities derived from dust emission with those calculated using the CO maps. We look for missing CO in the gas phase which we then assume to be the result of depletion.
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Peydro, Duclos Ignacio. "EVENT CLOUDS : lighter than air architectural structures." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91412.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Architecture, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 86-88).<br>EVENT CLOUD is a versatile covering system that allows events to happen independently to weather conditions. It consists of a lighter than air pneumatic structure, filled either with helium or hot air, that covers spaces by floating over them. Weightlessness permits EVENT CLOUD to theoretically cover an infinite surface, overcoming traditional large span structures proper weight limitation. EVENT CLOUD is a non-rigid aerodynamic balloon that can act as a fixed roof that does not overload the structure with weight. In this position events are protected from external weather conditions, converting any field into an interior climatically controlled space. If weather conditions are good the covering can be released from the anchoring system and let EVENT CLOUD float on the air. When EVENT CLOUD drifts in the air it becomes an urban reference, a visible object from around the city where the system is placed, and also a local clean energy source for the neighborhood. Creativity and design unite the functionality of a roof, the visual perception of an urban monument and the environmental action of locally producing energy to reduce carbon footprint of large events. EVENT CLOUD defeats gravity by enclosing within its boundaries a gas that weighs less than air to make the whole structure react to the medium it is placed in: air. This type of thinking implies the understanding that architecture creates objects that are inserted into a dynamical system within the fluid of space-time rather than isolated objects that only respond to compositional relations within themselves. Thus the design of EVENT CLOUD implies that architecture is a long-lived art discipline that has evolved from Beaux Arts compositional practices towards the post relativistic art of artificially manipulating the energetic and topological boundaries of events. Weightlessness provides the structure with a higher degree of versatility to allow EVENT CLOUD to nimbly respond to the requirements of each moment in space-time.<br>by Ignacio Peydro Duclos.<br>S.M.
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Nguyen, Anh Dung. "Contributions to Modeling, Structural Analysis, and Routing Performance in Dynamic Networks." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2013. http://tel.archives-ouvertes.fr/tel-00908502.
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Cette thèse apporte des contributions à la modélisation, compréhension ainsi qu'à la communication efficace d'information dans les réseaux dynamiques peuplant la périphérie de l'Internet. Par réseaux dynamiques, nous signifions les réseaux pouvant être modélisés par des graphes dynamiques dans lesquels noeuds et liens évoluent temporellement. Dans la première partie de la thèse, nous proposons un nouveau modèle de mobilité - STEPS - qui permet de capturer un large spectre de comportement de mobilité humains. STEPS mets en oeuvre deux principes fondamentaux de la mobilité humaine : l'attachement préférentiel à une zone de prédilection et l'attraction vers une zone de prédilection. Nous proposons une modélisation markovienne de ce modèle de mobilité. Nous montrons que ce simple modèle paramétrique est capable de capturer les caractéristiques statistiques saillantes de la mobilité humaine comme la distribution des temps d'inter-contacts et de contacts. Dans la deuxième partie, en utilisant STEPS, nous analysons les propriétés comportementales et structurelles fondamentales des réseaux opportunistes. Nous redéfinissons dans le contexte des réseaux dynamiques la notion de structure petit monde et montrons comment une telle structure peut émerger. En particulier, nous montrons que les noeuds fortement dynamiques peuvent jouer le rôle de ponts entre les composants déconnectés, aident à réduire significativement la longueur du chemin caractéristique du réseau et contribuent à l'émergence du phénomène petit-monde dans les réseaux dynamiques. Nous proposons une façon de modéliser ce phénomène sous STEPS. À partir d'un réseau dynamique régulier dans lequel les noeuds limitent leur mobilité à leurs zones préférentielles respectives. Nous recablons ce réseau en injectant progressivement des noeuds nomades se déplaçant entre plusieurs zones. Nous montrons que le pourcentage de tels nœuds nomades est de 10%, le réseau possède une structure petit monde avec un fort taux de clusterisation et un faible longueur du chemin caractéristique. La troisième contribution de cette thèse porte sur l'étude de l'impact du désordre et de l'irrégularité des contacts sur la capacité de communication d'un réseau dynamique. Nous analysons le degré de désordre de réseaux opportunistes réels et montrons que si exploité correctement, celui-ci peut améliorer significativement les performances du routage. Nous introduisons ensuite un modèle permettant de capturer le niveau de désordre d'un réseau dynamique. Nous proposons deux algorithmes simples et efficaces qui exploitent la structure temporelle d'un réseau dynamique pour délivrer les messages avec un bon compromis entre l'usage des ressources et les performances. Les résultats de simulations et analytiques montrent que ce type d'algorithme est plus performant que les approches classiques. Nous mettons également en évidence aussi la structure de réseau pour laquelle ce type d'algorithme atteint ses performances optimum. Basé sur ce résultat théorique nous proposons un nouveau protocole de routage efficace pour les réseaux opportunistes centré sur le contenu. Dans ce protocole, les noeuds maintiennent, via leurs contacts opportunistes, une fonction d'utilité qui résume leur proximité spatio-temporelle par rapport aux autres noeuds. En conséquence, router dans un tel contexte se résume à suivre le gradient de plus grande pente conduisant vers le noeud destination. Cette propriété induit un algorithme de routage simple et efficace qui peut être utilisé aussi bien dans un contexte d'adressage IP que de réseau centré sur les contenus. Les résultats de simulation montrent que ce protocole superforme les protocoles de routage classiques déjà définis pour les réseaux opportunistes. La dernière contribution de cette thèse consiste à mettre en évidence une application potentielle des réseaux dynamiques dans le contexte du " mobile cloud computing ". En utilisant les techniques d'optimisation particulaires, nous montrons que la mobilité peut augmenter considérablement la capacité de calcul des réseaux dynamiques. De plus, nous montrons que la structure dynamique du réseau a un fort impact sur sa capacité de calcul.
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Damiani, Rick R. "The structure of thermals in cumulus from airborne dual-Doppler radar observations." Laramie, Wyo. : University of Wyoming, 2005. http://proquest.umi.com/pqdweb?did=994244361&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Moreau, Julien. "Construction de modèles 3D à partir de données vidéo fisheye : application à la localisation en milieu urbain." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0290/document.
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Cette recherche vise à la modélisation 3D depuis un système de vision fisheye embarqué, utilisée pour une application GNSS dans le cadre du projet Predit CAPLOC. La propagation des signaux satellitaires en milieu urbain est soumise à des réflexions sur les structures, altérant la précision et la disponibilité de la localisation. L’ambition du projet est (1) de définir un système de vision omnidirectionnelle capable de fournir des informations sur la structure 3D urbaine et (2) de montrer qu’elles permettent d’améliorer la localisation.Le mémoire expose les choix en (1) calibrage automatique, (2) mise en correspondance entre images, (3) reconstruction 3D ; chaque algorithme est évalué sur images de synthèse et réelles. De plus, il décrit une manière de corriger les réflexions des signaux GNSS depuis un nuage de points 3D pour améliorer le positionnement. En adaptant le meilleur de l’état de l’art du domaine, deux systèmes sont proposés et expérimentés. Le premier est un système stéréoscopique à deux caméras fisheye orientées vers le ciel. Le second en est l’adaptation à une unique caméra.Le calibrage est assuré à travers deux étapes : l’algorithme des 9 points adapté au modèle « équisolide » couplé à un RANSAC, suivi d’un affinement par optimisation Levenberg-Marquardt. L’effort a été porté sur la manière d’appliquer la méthode pour des performances optimales et reproductibles. C’est un point crucial pour un système à une seule caméra car la pose doit être estimée à chaque nouvelle image.Les correspondances stéréo sont obtenues pour tout pixel par programmation dynamique utilisant un graphe 3D. Elles sont assurées le long des courbes épipolaires conjuguées projetées de manière adaptée sur chaque image. Une particularité est que les distorsions ne sont pas rectifiées afin de ne pas altérer le contenu visuel ni diminuer la précision. Dans le cas binoculaire il est possible d’estimer les coordonnées à l’échelle. En monoculaire, l’ajout d’un odomètre permet d’y arriver. Les nuages successifs peuvent être calés pour former un nuage global en SfM.L’application finale consiste dans l’utilisation du nuage 3D pour améliorer la localisation GNSS. Il est possible d’estimer l’erreur de pseudodistance d’un signal après multiples réflexions et d’en tenir compte pour une position plus précise. Les surfaces réfléchissantes sont modélisées grâce à une extraction de plans et de l’empreinte des bâtiments. La méthode est évaluée sur des paires d’images fixes géo-référencées par un récepteur bas-coût et un récepteur GPS RTK (vérité terrain). Les résultats montrent une amélioration de la localisation en milieu urbain<br>This research deals with 3D modelling from an embedded fisheye vision system, used for a GNSS application as part of CAPLOC project. Satellite signal propagation in urban area implies reflections on structures, impairing localisation’s accuracy and availability. The project purpose is (1) to define an omnidirectional vision system able to provide information on urban 3D structure and (2) to demonstrate that it allows to improve localisation.This thesis addresses problems of (1) self-calibration, (2) matching between images, (3) 3D reconstruction ; each algorithm is assessed on computer-generated and real images. Moreover, it describes a way to correct GNSS signals reflections from a 3D point cloud to improve positioning. We propose and evaluate two systems based on state-of-the-art methods. First one is a stereoscopic system made of two sky facing fisheye cameras. Second one is the adaptation of the former to a single camera.Calibration is handled by a two-steps process: the 9-point algorithm fitted to “equisolid” model coupled with a RANSAC, followed by a Levenberg-Marquardt optimisation refinement. We focused on the way to apply the method for optimal and repeatable performances. It is a crucial point for a system composed of only one camera because the pose must be estimated for every new image.Stereo matches are obtained for every pixel by dynamic programming using a 3D graph. Matching is done along conjugated epipolar curves projected in a suitable manner on each image. A distinctive feature is that distortions are not rectified in order to neither degrade visual content nor to decrease accuracy. In the binocular case it is possible to estimate full-scale coordinates.In the monocular case, we do it by adding odometer information. Local clouds can be wedged in SfM to form a global cloud.The end application is the usage of the 3D cloud to improve GNSS localisation. It is possible to estimate and consider a signal pseudodistance error after multiple reflections in order to increase positioning accuracy. Reflecting surfaces are modelled thanks to plane and buildings trace fitting. The method is evaluated on fixed image pairs, georeferenced by a low-cost receiver and a GPS RTK receiver (ground truth). Study results show the localisation improvement ability in urban environment
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Neeli, Yeshwanth Sai. "Use of Photogrammetry Aided Damage Detection for Residual Strength Estimation of Corrosion Damaged Prestressed Concrete Bridge Girders." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99445.
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Corrosion damage reduces the load-carrying capacity of bridges which poses a threat to passenger safety. The objective of this research was to reduce the resources involved in conventional bridge inspections which are an important tool in the condition assessment of bridges and to help in determining if live load testing is necessary. This research proposes a framework to link semi-automated damage detection on prestressed concrete bridge girders with the estimation of their residual flexural capacity. The framework was implemented on four full-scale corrosion damaged girders from decommissioned bridges in Virginia. 3D point clouds of the girders reconstructed from images using Structure from Motion (SfM) approach were textured with images containing cracks detected at pixel level using a U-Net (Fully Convolutional Network). Spalls were detected by identifying the locations where normals associated with the points in the 3D point cloud deviated from being perpendicular to the reference directions chosen, by an amount greater than a threshold angle. 3D textured mesh models, overlaid with the detected cracks and spalls were used as 3D damage maps to determine reduced cross-sectional areas of prestressing strands to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011). Scaling them to real-world dimensions enabled the measurement of any required dimension, eliminating the need for physical contact.
The flexural capacities of a box beam and an I-beam estimated using strain compatibility analysis were validated with the actual capacities at failure sections determined from four destructive tests conducted by Al Rufaydah (2020). Along with the reduction in the cross-sectional areas of strands, limiting the ultimate strain that heavily corroded strands can develop was explored as a possible way to improve the results of the analysis. Strain compatibility analysis was used to estimate the ultimate rupture strain, in the heavily corroded bottommost layer prestressing strands exposed before the box beam was tested. More research is required to associate each level of strand corrosion with an average ultimate strain at which the corroded strands rupture. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.<br>Master of Science<br>Corrosion damage is a major concern for bridges as it reduces their load carrying capacity. Bridge failures in the past have been attributed to corrosion damage. The risk associated with corrosion damage caused failures increases as the infrastructure ages. Many bridges across the world built forty to fifty years ago are now in a deteriorated condition and need to be repaired and retrofitted. Visual inspections to identify damage or deterioration on a bridge are very important to assess the condition of the bridge and determine the need for repairing or for posting weight restrictions for the vehicles that use the bridge. These inspections require close physical access to the hard-to-reach areas of the bridge for physically measuring the damage which involves many resources in the form of experienced engineers, skilled labor, equipment, time, and money. The safety of the personnel involved in the inspections is also a major concern. Nowadays, a lot of research is being done in using Unmanned Aerial Vehicles (UAVs) like drones for bridge inspections and in using artificial intelligence for the detection of cracks on the images of concrete and steel members.
Girders or beams in a bridge are the primary longitudinal load carrying members. Concrete inherently is weak in tension. To address this problem, High Strength steel reinforcement (called prestressing steel or prestressing strands) in prestressed concrete beams is pre-loaded with a tensile force before the application of any loads so that the regions which will experience tension under the service loads would be subjected to a pre-compression to improve the performance of the beam and delay cracking. Spalls are a type of corrosion damage on concrete members where portions of concrete fall off (section loss) due to corrosion in the steel reinforcement, exposing the reinforcement to the environment which leads to accelerated corrosion causing a loss of cross-sectional area and ultimately, a rupture in the steel. If the process of detecting the damage (cracks, spalls, exposed or severed reinforcement, etc.) is automated, the next logical step that would add great value would be, to quantify the effect of the damage detected on the load carrying capacity of the bridges. Using a quantified estimate of the remaining capacity of a bridge, determined after accounting for the corrosion damage, informed decisions can be made about the measures to be taken. This research proposes a stepwise framework to forge a link between a semi-automated visual inspection and residual capacity evaluation of actual prestressed concrete bridge girders obtained from two bridges that have been removed from service in Virginia due to extensive deterioration.
3D point clouds represent an object as a set of points on its surface in three dimensional space. These point clouds can be constructed either using laser scanning or using Photogrammetry from images of the girders captured with a digital camera. In this research, 3D point clouds are reconstructed from sequences of overlapping images of the girders using an approach called Structure from Motion (SfM) which locates matched pixels present between consecutive images in the 3D space. Crack-like features were automatically detected and highlighted on the images of the girders that were used to build the 3D point clouds using artificial intelligence (Neural Network). The images with cracks highlighted were applied as texture to the surface mesh on the point cloud to transfer the detail, color, and realism present in the images to the 3D model. Spalls were detected on 3D point clouds based on the orientation of the normals associated with the points with respect to the reference directions. Point clouds and textured meshes of the girders were scaled to real-world dimensions facilitating the measurement of any required dimension on the point clouds, eliminating the need for physical contact in condition assessment. Any cracks or spalls that went unidentified in the damage detection were visible on the textured meshes of the girders improving the performance of the approach. 3D textured mesh models of the girders overlaid with the detected cracks and spalls were used as 3D damage maps in residual strength estimation.
Cross-sectional slices were extracted from the dense point clouds at various sections along the length of each girder. The slices were overlaid on the cross-section drawings of the girders, and the prestressing strands affected due to the corrosion damage were identified. They were reduced in cross-sectional area to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011) and were used in the calculation of the ultimate moment capacity of the girders using an approach called strain compatibility analysis. Estimated residual capacities were compared to the actual capacities of the girders found from destructive tests conducted by Al Rufaydah (2020). Comparisons are presented for the failure sections in these tests and the results were analyzed to evaluate the effectiveness of this framework. More research is to be done to determine the factors causing rupture in prestressing strands with different degrees of corrosion. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.