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1
Mariani, Patrizia. "Caratterizzazione della struttura litosferica del bacino intracratonico del Parana' (Sud America) mediante modellazione di dati gradiometrici e gravimetrici da satelliti di nuova generazione (GRACE e GOCE)." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7393.
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2010/2011Riassunto: La finalità di questo studio è la caratterizzazione della litosfera sottostante il bacino intracratonico del Paraná. I modelli gravimetrici adottati sono vincolati ai dati geofisici tra i quali quelli sismologici più recenti (Lloyd et al., 2010) e sono corroborati dai modelli petrografici (Bryan & Ernst, 2008). Si offre un approccio che include la comparazione isostatica a quella sismologica al fine di interpretare al meglio la struttura litosferica nell’area del bacino in analisi e di comprendere le variazioni geodinamiche legate alle province geologiche ivi presenti. Il bacino del Paraná (Sud America) è ubicato nella piattaforma stabile del Sud America, ed è circondato da cratoni tra i quali: il cratone amazzonico, il cratone di San Francisco e il Rio de La Plata. La sua genesi in epoca paleozoica è quella di vasto bacino sedimentario, sul quale però durante il Mesozoico (Cretaceo inferiore) si è sviluppata un’intensa attività vulcanica (Capitolo 3). Quest’attività effusiva lo classifica tra le maggiori LIP (Large Igneous Province) mondiali, provincie magmatiche con volume di materiale espulso superiore a 0.1 Mkm3 (Bryan & Ernst, 2008). L’analisi effettuata in questo lavoro è eseguita tramite lo studio del campo gravimetrico da modelli di nuova generazione derivanti dal satellite GOCE (Gravity field and steady state Ocean Circulation Explorer) e GRACE (Gravity Recovery and Climate Experiment). I prodotti gravimetrici satellitari di GOCE possiedono una risoluzione senza precedenti (mezza lunghezza d’onda 80 km): ciò consente di validare i modelli gravimetrici precedenti (280 km, EGM08, Pavlis et al., 2008) che per offrire una maggior dettaglio nelle anomalie integravano ai dati satellitari di GRACE le campagne gravimetriche terrestri, non sempre complete e quindi globalmente precise e di adempire agli indispensabile fini di interpretazione geodinamica. La descrizione dei modelli e la validazione degli stessi sono offerte nel Capitolo 2. I campi potenziali studiati per le principali province geologiche sono illustrati nel Capitolo 5; mentre nel Capitolo 6 si applica la metodologia spettrale sulla seconda derivata verticale del potenziale per discernere le diverse litologie individuate nell’area di studio. L’anomalia di Bouguer calcolata tramite sviluppo in armoniche sferiche viene corretta sia in superficie e in profondità stimando l’effetto di gravità dei sedimenti conosciuti (Capitolo 4) e le conoscenze geofisiche note. Il bacino è composto da: i sedimenti pre-vulcanici paleozoici di spessore pari a circa 3500 m, la Formazione Serra Geral composta principalmente da basalti tholeiitici del cretaceo inferiore (~1500 m di spessore), ed infine i sedimenti post-vulcanici del cretaceo superiore appartenenti al Gruppo Bauru, solo 300 m di spessore (Capitolo 3). Sfruttando i modelli sismologici regionali è stato infine possibile valutare anche il contributo gravimetrico dello spessore crostale stimato con la sismologia. Con questi elementi viene calcolata la Bouguer residua, che è interpretata come anomalia isostatica e quindi correlata alle strutture geologiche locali e regionali. Questo comporta il riconoscimento di una struttura anomala sotto la parte settentrionale del bacino del Paraná comprendente anche parte del settore adiacente Blocco del Guaporé. L’inquadramento a scala maggiore però permette di evidenziare un’area molto più ampia di quanto riconosciuto in prima istanza. Tale anomalia è centrata infatti nel nucleo archeano del cratone amazzonico, di cui quindi il bacino del Paraná risulta solamente il suo braccio più meridionale. In assenza di attività tettonica-magmatica recente (ultima risale 50 Ma) ed in mancanza di grandi anomalie superficiali, tale anomalia positiva potrebbe essere inserita in un contesto regionale e più profondo, rappresentando delle dinamiche di mantello. Infine tramite inversione gravimetrica è stata quantificata numericamente l’anomalia nel bacino di studio utilizzando la geometria semplice di un tronco di cono. La quantità di materiale in presunto underplating che dovrebbe spiegare l’anomalia positiva è compatibile ai modelli petrografici conosciuti. Tali modelli sottolineano come la presenza di un magmatismo noto in superficie rappresenti solo una piccola parte di quello che dovrebbe trovarsi in intrusione: è stato calcolato infatti che il magmatismo superficiale potrebbe rappresentare solo la decima parte di quello associato in profondità.
Abstract: Goal of this study is the characterization of the lithosphere beneath the intracratonic area of Paraná basin. We formulate gravimetric models constrained by geophysical data and new seismological models (Lloyd et al., 2010) and also underpinned by petrographic models (Bryan & Ernst, 2008). Our approach includes isostatic Moho to seismological Moho comparison to better understand lithospheric structures in the area of basin, and geodynamic context of the local geological province. Paraná basin (South America) is located on the stable South American platform, and it is surrounded by some craton areas, as: the Amazon craton, the San Francisco craton and the Rio de La Plata Craton. During Paleozoic epoch the Paraná region was a wide sedimentary basin, while in the Mesozoic (Early Cretaceous) a significant volcanic activity developed on it. This effusive phase classifies the basin between the greatest LIP (Large Igneous Province) worldwide known, where the magmatism volume is greater than 0.1 Mkm3(Bryan & Ernst, 2008). We analyzed gravimetric field using new generation satellite models as GOCE (Gravity field and steady-state Ocean Circulation Explorer) and GRACE (Gravity Recovery and Climate Experiment). GOCE’s products gives unprecedented resolution (half wavelength: 80 km) helping to validate previous global gravity models as EGM08 (Pavlis et al., 2008). The 280 km satellite- only resolution was increased by integration of terrestrial gravity fields data, but this methodology added some problems during processing, where the terrestrial information is not complete or precise. On Chapter 2 some descriptions and validation among models are shown. We calculated potential field for the main geological provinces of Chapter 5; while in Chapter 6, using spectral methodology on the second vertical derivatives of potential field, we identify main lithologic units. The Bouguer anomaly calculated with the spherical harmonics expansion of the potential field is corrected by known stratigraphic units. The basin is made by pre-volcanic sediments of Paleozoic age, with over 3500 m of thickness, Serra Geral Formation, mainly tholeiitic basalts of Early Cretaceous (~1500 m), and post-volcanic sediment of Bauru Group, only 300 m of thickness. We evaluate the effect of crustal thickness variations on the gravity field by using the seismological crustal model. Removing these elements from the Bouguer anomaly, we obtain the residual Bouguer anomaly. Further we calculate the isostatic anomaly and we correlate it to the local and regional geological framework. This helps to recognize a positive residual anomaly on the northern part of the Paraná basin, including the nearby Guaporé Block. Setting a major scale we see the same phenomenon: it is in agreement with the archean nucleus of the Amazon craton, so we can claim that the anomaly on the Paraná is only the southern part of a greater positive area. The relative gravity positive anomaly in the Paraná basin is not very extended and lack of tectonic activity since50 Ma makes us consider that this anomaly is part of a deeper and greater anomaly, maybe due to mantle dynamic effects. We quantified the intracrustal density anomaly using gravity inversion and adopting a truncated cone geometry and volume in accord to petrographic models. It is known that an underplated magmatic body can be up to 10 time larger than the associated extrusive volume and this corroborates our models.
XXIV Ciclo
1979
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Lerisson, Gaétan. "Stabilité d'une onde de gravité interne, analyse locale, globale et croissance transitoire." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX017/document.
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Dans les océans profonds linéairement stratifiés, la déstabilisation des ondes de gravité internes est importante car elle contribue probablement au mélange turbulent et à la circulation thermohaline.À l'aide de simulations numériques directes, nous créons un faisceau d'onde interne progressive. Cette situation est équivalente à une onde produite par l'oscillation de la marée sur une topographie sous-marine. Nous retrouvons les résultats expérimentaux obtenus par cite{Bourget13} : le faisceau se déstabilise en un mode petite échelle. Nous regardons l'effet d'un écoulement horizontal moyen sur cette instabilité en prenant soin d'abaisser la fréquence de forçage afin de compenser l'effet doppler et de conserver localement la même onde. Un cas limite apparaît lorsque le forçage devient stationnaire, ce qui équivaut à une onde de sillage issue d'un écoulement constant au dessus d'une topographie.Les écoulements à petite vitesse voient une instabilité petite échelle similaire au cas marée alors que les écoulement intermédiaires restent stables. Les écoulements plus rapides (jusqu'au cas sillage) voient, par contre, une instabilité bien plus grande échelle que celle dans le cas marée. Cette sélection d'échelle est robuste aux variations du nombre de Froude, de Reynolds, de la taille du faisceau ou de l'angle de l'onde.Nous montrons que ces instabilités peuvent être décrites comme des triades résonantes et que les différentes échelles correspondent à différentes branches triadiques. Nous confirmons la présence de cas stables pour des vitesses intermédiaires en calculant les modes propres comme des modes de Floquet à l'aide d'un algorithme d'Arnoldi--Krylov, et en montrant qu'ils sont associés à des taux de croissance négatifs.Le cas sillage est instable et nous le stabilisons par une méthode deselective frequency damping cite{Akervik06} afin d'obtenir un écoulement de base stationnaire autour duquel nous calculons les perturbations optimales qui maximisent l'énergie totale à différents horizons temporels. Pour des horizons courts, la perturbation optimale est petite échelle alors que pour des horizons longs, elle est grande échelle et converge vers la solution non-linéaire obtenue précédemment. Les horizons courts voient une instabilité triadique petite échelle advectée par l'écoulement et les horizons longs développent une instabilité d'une branche triadique grande échelle capable de se maintenir dans le faisceau malgré l'écoulement.Nous interprétons cette sélection de mode par le biais de la théorie des instabilités absolue ou convective. Dans le cas de l'onde de sillage l'instabilité grande échelle est absolue alors que la petite échelle est convective (et domine la croissance transitoire puisque son taux de croissance local est supérieur). Les rôles s'inversent dans le cas marée et l'instabilité petit échelle devient absolue alors que la grande échelle est convective. Nous confirmons cette hypothèse en calculant la réponse impulsionnelle d'une onde plane monochromatique dans un domaine 2Dpériodique. L'évolution spatio-temporelle d'une perturbation localisée en temps et en espace montre la formation de trois paquets d'onde, chacun étant associé à une branche triadique que nous identifions par une extension de la théorie triadique prenant en compte un désaccordage cite{McEwan77} et permettant de calculer la vitesse de groupe des sommets des paquets. En calculant ensuite le taux de croissance absolu le long de rayons à x/t et z/t constant, nous validons notre hypothèseInternal gravity waves that exist in a continuously stratified fluid are particularly important in the ocean. They transport energy and are thought to generate turbulent mixing, which contribute to the deep ocean circulation.We generate an internal wave beam that propagates in a continuously stratified fluid with direct numerical simulations. This situation is equivalent to a tidal wave, where the tidal flow oscillates over a topography and generates a wave. Experimental results obtained by cite{Bourget13} are recovered, ie. the beam destabilizes into a small scale mode. We consider the effect of an horizontal mean flow on the instability and lower the forcing frequency in order to compensate for the doppler effect and to keep locally the same wave. A limit case appears when the forcing becomes stationary. This case is equivalent to a lee wave appearing when a stratified fluid flows over a topography.For small mean flow, small scale instabilities develop as in the tidal case. The beam then stabilizes at intermediate mean flows and destabilizes again for increasing flow speed. At this second threshold, down to the lee wave case, the instability is of much larger scale than for the tidal case. Varying the Reynolds number, the Froude number, the wave angle or the beam size doesn't affect the instability scale selection : a small scale instability in the tidal regime, and large scale instability in the lee regime.We show that the instability mechanism may be interpreted using the triadic instability. Scale selection corresponds to different branches of triadic resonance. We confirm the presence of a stability region for intermediate value of the mean advection velocity by computing the linear eigenmode as Floquet mode with an Arnoldi-Krylov technique and show that the leading eigenmode has a negative growth rate.In the lee wave, case the flow is unstable and a selective frequency damping method cite{Akervik06} is used to compute a steady base flow. We then implement a linear direct-adjoint method to compute the optimal perturbations that maximizes the total energy at different time horizons. At short time horizon, the optimal perturbation is small scale while at large time the perturbation switches to a large scale solution and converges to the large scale mode observed through the nonlinear simulations. Short time transients correspond to the small scale triadic instability advected by the flow whereas the long time large scale instability corresponds to large scale branch of the triadic instability that is able to sustain the flow.We propose an interpretation of the selection of these different instabilities in term of absolute and convective instability. In the case of the lee wave, the large scale instability is absolute whereas the small scale instability is convective (and dominates the short time transient growth because it has a larger local growth rate). When the mean flow is varied, the properties of small scale and large scale instabilities exchange: in the tidal case the short scale instability is absolute and the large scale convective. This conjecture is confirmed by computing the impulse response around a plane monochromatic internal gravity wave in an extended two dimensional periodic domain. The spatio temporal evolution of a perturbation localized in space and time points out the formation of three different wave packets corresponding to different branches of triadic instability. Using the triadic theory with finite detuning cite{McEwan77},we derive the group velocity at the maximum growth rate of the three different branches of triadic instability and find a good agreement with the velocity of the three wave paquet maxima in the impulse response. Analyzing the impulse response along rays, i.e. at x/t and z/tconstant, we compute the absolute growth rate along all possible rays and validate our conjecture
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Ceriotti, Matteo. "Global optimisation of multiple gravity assist trajectories." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/2003/.
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Multiple gravity assist (MGA) trajectories represent a particular class of space trajectories in which a spacecraft exploits the encounter with one or more celestial bodies to change its velocity vector; they have been essential to reach high Delta-v targets with low propellant consumption. The search for optimal transfer trajectories can be formulated as a mixed combinatorial-continuous global optimisation problem; however, it is known that the problem is difficult to solve, especially if deep space manoeuvres (DSM) are considered. This thesis addresses the automatic design of MGA trajectories through global search techniques, in answer to the requirements of having a large number of mission options in a short time, during the preliminary design phase. Two different approaches are presented. The first is a two-level approach: a number of feasible planetary sequences are initially generated; then, for each one, families of the MGA trajectories are built incrementally. The whole transfer is decomposed into sub-problems of smaller dimension and complexity, and the trajectory is progressively composed by solving one problem after the other. At each incremental step, a stochastic search identifies sets of feasible solutions: this region is preserved, while the rest of the search space is pruned out. The process iterates by adding one planet-to-planet leg at a time and pruning the unfeasible portion of the solution space. Therefore, when another leg is added to the trajectory, only the feasible set for the previous leg is considered and the search space is reduced. It is shown, through comparative tests, how the proposed incremental search performs an effective pruning of the search space, providing families of optimal solutions with a lower computational cost than a non-incremental approach. Known deterministic and stochastic methods are used for the comparison. The algorithm is applied to real MGA case studies, including the ESA missions BepiColombo and Laplace. The second approach performs an integrated search for the planetary sequence and the associated trajectories. The complete design of an MGA trajectory is formulated as an autonomous planning and scheduling problem. The resulting scheduled plan provides the planetary sequence for a MGA trajectory and a good estimation of the optimality of the associated trajectories. For each departure date, a full tree of possible transfers from departure to destination is generated. An algorithm inspired by Ant Colony Optimization (ACO) is devised to explore the space of possible plans. The ants explore the tree from departure to destination, adding one node at a time, using a probability function to select one of the feasible directions. Unlike standard ACO, a taboo-based heuristics prevents ants from re-exploring the same solutions. This approach is applied to the design of optimal transfers to Saturn (inspired by Cassini) and to Mercury, and it demonstrated to be very competitive against known traditional stochastic population-based techniques.
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Werth, Susanna. "Calibration of the global hydrological model WGHM with water mass variations from GRACE gravity data." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4173/.
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Since the start-up of the GRACE (Gravity Recovery And Climate Experiment) mission in 2002 time dependent global maps of the Earth's gravity field are available to study geophysical and climatologically-driven mass redistributions on the Earth's surface. In particular, GRACE observations of total water storage changes (TWSV) provide a comprehensive data set for analysing the water cycle on large scales. Therefore they are invaluable for validation and calibration of large-scale hydrological models as the WaterGAP Global Hydrology Model (WGHM) which simulates the continental water cycle including its most important components, such as soil, snow, canopy, surface- and groundwater. Hitherto, WGHM exhibits significant differences to GRACE, especially for the seasonal amplitude of TWSV. The need for a validation of hydrological models is further highlighted by large differences between several global models, e.g. WGHM, the Global Land Data Assimilation System (GLDAS) and the Land Dynamics model (LaD).
For this purpose, GRACE links geodetic and hydrological research aspects. This link demands the development of adequate data integration methods on both sides, forming the main objectives of this work. They include the derivation of accurate GRACE-based water storage changes, the development of strategies to integrate GRACE data into a global hydrological model as well as a calibration method, followed by the re-calibration of WGHM in order to analyse process and model responses.
To achieve these aims, GRACE filter tools for the derivation of regionally averaged TWSV were evaluated for specific river basins. Here, a decorrelation filter using GRACE orbits for its design is most efficient among the tested methods. Consistency in data and equal spatial resolution between observed and simulated TWSV were realised by the inclusion of all most important hydrological processes and an equal filtering of both data sets. Appropriate calibration parameters were derived by a WGHM sensitivity analysis against TWSV. Finally, a multi-objective calibration framework was developed to constrain model predictions by both river discharge and GRACE TWSV, realised with a respective evolutionary method, the ε-Non-dominated-Sorting-Genetic-Algorithm-II (ε-NSGAII).
Model calibration was done for the 28 largest river basins worldwide and for most of them improved simulation results were achieved with regard to both objectives. From the multi-objective approach more reliable and consistent simulations of TWSV within the continental water cycle were gained and possible model structure errors or mis-modelled processes for specific river basins detected. For tropical regions as such, the seasonal amplitude of water mass variations has increased. The findings lead to an improved understanding of hydrological processes and their representation in the global model. Finally, the robustness of the results is analysed with respect to GRACE and runoff measurement errors. As a main conclusion obtained from the results, not only soil water and snow storage but also groundwater and surface water storage have to be included in the comparison of the modelled and GRACE-derived total water budged data. Regarding model calibration, the regional varying distribution of parameter sensitivity suggests to tune only parameter of important processes within each region. Furthermore, observations of single storage components beside runoff are necessary to improve signal amplitudes and timing of simulated TWSV as well as to evaluate them with higher accuracy.
The results of this work highlight the valuable nature of GRACE data when merged into large-scale hydrological modelling and depict methods to improve large-scale hydrological models.Das Schwerefeld der Erde spiegelt die Verteilung von Massen auf und unter der Erdoberfläche wieder. Umverteilungen von Erd-, Luft- oder Wassermassen auf unserem Planeten sind damit über eine kontinuierliche Vermessung des Erdschwerefeldes beobachtbar. Besonders Satellitenmissionen sind hierfür geeignet, da deren Umlaufbahn durch zeitliche und räumliche Veränderung der Schwerkraft beeinflusst wird. Seit dem Start der Satellitenmission GRACE (Gravity Recovery And Climate Experiment) im Jahr 2002 stellt die Geodäsie daher globale Daten von zeitlichen Veränderungen des Erdschwerefeldes mit hoher Genauigkeit zur Verfügung. Mit diesen Daten lassen sich geophysikalische und klimatologische Massenumverteilungen auf der Erdoberfläche studieren. GRACE liefert damit erstmals Beobachtungen von Variationen des gesamten kontinentalen Wasserspeichers, welche außerordentlich wertvoll für die Analyse des Wasserkreislaufes über große Regionen sind. Die Daten ermöglichen die Überprüfung von großräumigen mathematischen Modellen der Hydrologie, welche den natürlichen Kreislauf des Wassers auf den Kontinenten, vom Zeitpunkt des Niederschlags bis zum Abfluss in die Ozeane, nachvollziehbar machen. Das verbesserte Verständnis über Transport- und Speicherprozesse von Süßwasser ist für genauere Vorhersagen über zukünftige Wasserverfügbarkeit oder potentielle Naturkatastrophen, wie z.B. Überschwemmungen, von enormer Bedeutung. Ein globales Modell, welches die wichtigsten Komponenten des Wasserkreislaufes (Boden, Schnee, Interzeption, Oberflächen- und Grundwasser) berechnet, ist das "WaterGAP Global Hydrology Model" (WGHM). Vergleiche von berechneten und beobachteten Wassermassenvariationen weisen bisher insbesondere in der jährlichen Amplitude deutliche Differenzen auf. Sehr große Unterschiede zwischen verschiedenen hydrologischen Modellen betonen die Notwendigkeit, deren Berechnungen zu verbessern. Zu diesem Zweck verbindet GRACE die Wissenschaftsbereiche der Geodäsie und der Hydrologie. Diese Verknüpfung verlangt von beiden Seiten die Entwicklung geeigneter Methoden zur Datenintegration, welche die Hauptaufgaben dieser Arbeit darstellten. Dabei handelt es sich insbesondere um die Auswertung der GRACE-Daten mit möglichst hoher Genauigkeit sowie um die Entwicklung einer Strategie zur Integration von GRACE Daten in das hydrologische Modell. Mit Hilfe von GRACE wurde das Modell neu kalbriert, d.h. Parameter im Modell so verändert, dass die hydrologischen Berechnungen besser mit den GRACE Beobachtungen übereinstimmen. Dabei kam ein multikriterieller Kalibrieralgorithmus zur Anwendung mit dem neben GRACE-Daten auch Abflussmessungen einbezogen werden konnten. Die Modellkalibierung wurde weltweit für die 28 größten Flusseinzugsgebiete durchgeführt. In den meisten Fällen konnte eine verbesserte Berechnung von Wassermassenvariationen und Abflüssen erreicht werden. Hieraus ergeben sich, z.B. für tropische Regionen, größere saisonale Variationen. Die Ergebnisse führen zu einem verbesserten Verständnis hydrologischer Prozesse. Zum Schluss konnte die Robustheit der Ergebnisse gegenüber Fehlern in GRACE- und Abflussmessungen erfolgreich getestet werden. Nach den wichtigsten Schlussfolgerungen, die aus den Ergebnissen abgeleitet werden konnten, sind nicht nur Bodenfeuchte- und Schneespeicher, sondern auch Grundwasser- und Oberflächenwasserspeicher in Vergleiche von berechneten und GRACE-beobachteten Wassermassenvariationen einzubeziehen. Weiterhin sind neben Abflussmessungen zusätzlich Beobachtungen von weiteren hydrologischen Prozessen notwendig, um die Ergebnisse mit größerer Genauigkeit überprüfen zu können. Die Ergebnisse dieser Arbeit heben hervor, wie wertvoll GRACE-Daten für die großräumige Hydrologie sind und eröffnen eine Methode zur Verbesserung unseres Verständnisses des globalen Wasserkreislaufes.
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Dando, Owen Robert. "Topological defects in low-energy string gravity." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4496/.
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Cosmologists are interested in topological defects as a possible source for the primordial density perturbations which seeded structure formation through gravitational instability. In this thesis, the gravitational properties of various topological defects are studied in the context of low-energy string theory, a likely modification of Einstein gravity at the high energy scales prevalent in the early universe. We consider in turn global monopole, local monopole, global cosmic string and global texture defects, allowing for an arbitrary coupling of defects to the string theory dilaton. For global defects we find the following behaviour. If the dilaton is massless, this modification to general relativity generically destroys the global good behaviour of the monopole and cosmic string, making their spacetimes singular. For the texture non-singular spacetimes exist, but only for certain values of the matter-dilaton coupling, dependent on the gravitational strength of the defect; in addition, this non-singular behaviour exists only in a certain frame. In the case of a massive dilaton, the metric behaviour of these defects is similar to that found in Einstein gravity, though we find they generically induce a long-range dilaton cloud. For the local monopole, which we study only in the presence of a massless dilaton, a rich variety of behaviour is found. For particular parameter values the local monopole spacetime approximates that of an extremal dilaton black hole.
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Han, Shin-Chan. "Efficient global gravity field determination from satellite-to-satellite tracking." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1061995200.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xvii, 198 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Christopher Jekeli, Dept. of Geodetic Science and Surveying. Includes bibliographical references (p. 192-198).
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Bai, Lu. "Effects of global financial crisis on Chinese export: a gravity model study." Thesis, Internationella Handelshögskolan, Högskolan i Jönköping, IHH, Economics, Finance and Statistics, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-18297.
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Wöhr, Andreas J. [Verfasser], and Stefan [Akademischer Betreuer] Teufel. "Global Formalism of Loop Quantum Gravity / Andreas J. Wöhr ; Betreuer: Stefan Teufel." Tübingen : Universitätsbibliothek Tübingen, 2014. http://d-nb.info/1163236373/34.
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Wan, Mohd Akib Wan Abdul Aziz. "A preliminary determination of a gravimetric geoid in Peninsular Malaysia." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283665.
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Beres, Jadwiga H. "Gravity waves generated by tropical convection : generation mechanisms and implications for global circulation models /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10048.
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Li, Xiaopeng. "Moving base INS/GPS vector gravimetry on a land vehicle." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195677222.
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Crespo, Cuaresma Jesus, Mathias Moser, and Anna Raggl. "On the Determinants of Global Bilateral Migration Flows." European Commission, bmwfw, 2013. http://epub.wu.ac.at/4715/1/WWWforEurope_WPS_no005_MS14.pdf.
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We present a method aimed at estimating global bilateral migration flows and assessing their determinants. We employ that fact that available net migration figures for a country are (nonlinear) aggregates of migration flows from and to all other countries of the world in order to construct a statistical model that links the determinants of (unobserved) migration ows to total net migration. Using simple specifications based on the gravity model for international migration, we find that migration flows can be explained by standard gravity model variables such as GDP differences, distance or bilateral population. The usefulness of such models is exemplified by combining estimated specifications with population and GDP projections in order to assess quantitatively the expected changes in migration flows to Europe in the coming decades.Series: WWWforEurope
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Liu, Xianglin. "Global gravity field recovery from satellite-to-satellite tracking data with the acceleration approach /." Delft : NCG Nederlandse Commissie voor Geodesie, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9789061323096.
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Bergmann-Wolf, Inga [Verfasser]. "Oceanographic applications of GRACE gravity data on global and regional scales / Inga Bergmann-Wolf." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1082237965/34.
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Cai, Zhiyuan. "Global Mohorovicic Discontinuity Estimates Based on Isostatic Theories Using Gravity Data and Seismic Models." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu159455139426099.
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Bryan, Jason M. "GLOBAL OPTIMIZATION OF MGA-DSM PROBLEMS USING THE INTERPLANETARY GRAVITY ASSIST TRAJECTORY OPTIMIZER (IGATO)." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/663.
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Interplanetary multiple gravity assist (MGA) trajectory optimization has long been a field of interest to space scientists and engineers. Gravity assist maneuvers alter a spacecraft's velocity vector and potentially allow spacecraft to achieve changes in velocity which would otherwise be unfeasible given our current technological limitations. Unfortunately, designing MGA trajectories is difficult and in order to find good solutions, deep space maneuvers (DSM) are often required which further increase the complexity of the problem. In addition, despite the active research in the field over the last 50 years, software for MGA trajectory optimization is scarce. A few good commercial, and even fewer open-source, options exist, but a majority of quality software remains proprietary.
The intent of this thesis is twofold. The first part of this work explores the realm of global optimization applied to multiple gravity assist trajectories with deep space maneuvers (MGA-DSM). With the constant influx of new global optimization algorithms and heuristics being developed in the global optimization community, this work aims to be a high level optimization approach which makes use of those algorithms instead of trying to be one itself. Central to this approach is PaGMO, which is the open-source Parallel Multiobjective Global Optimizer created by ESA's Advanced Concepts Team (ACT). PaGMO is an implementation of the Island Model Paradigm which allows the parallelization of different global optimizers. The second part of this work introduces the IGATO software which improves PaGMO by complementing it with dynamic restart capabilities, a pruning algorithm which learns over time, subdomain decomposition, and other techniques to create a powerful optimization tool. IGATO aims to be an open-source platform independent C++ application with a robust graphical user interface (GUI). The application is equipped with 2D plotting and simulations, real time Porkchop Plot generation, and other useful features for analyzing various problems. The optimizer is tested on several challenging MGA-DSM problems and performs well: consistently performing as well or better than PaGMO on its own.
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Brockmann, Jan Martin [Verfasser]. "On High Performance Computing in Geodesy : Applications in Global Gravity Field Determination / Jan Martin Brockmann." Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1077268998/34.
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Baier, Fabian [Verfasser]. "A Gravity Approach to Regional and Global Investment Dynamics: Theory and Empirical Findings / Fabian Baier." Wuppertal : Universitätsbibliothek Wuppertal, 2019. http://d-nb.info/1206120916/34.
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Trinh, Quang Thai [Verfasser]. "Properties of convective gravity waves derived by combining global modeling and satellite observations / Quang Thai Trinh." Wuppertal : Universitätsbibliothek Wuppertal, 2016. http://d-nb.info/1120027616/34.
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Holland, Steven K. "Toward a More Inclusive Construct of Native Chinese Speaker L2 Written Error Gravity." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3477.
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The purpose of this study is to determine two types of error gravity in a corpus of texts written by native Chinese learners of English (ELLs)—one that enriches the traditional construct of gravity found in error gravity research by including error frequency, or how often an error occurs in a text relative to others, as an intervening variable, and one that applies the new error gravity data in a practical way to help establish salient grammatical focal points for written corrective feedback (WCF). Previous error gravity research has suggested that the amount of irritation caused by error is determined by the extent to which an utterance departs from "native-like" speech. However, because these studies often neglect the role of frequency in determining gravity—relying on isolated sentences, pre-determined errors, and manipulated texts to define it—a more complete view of error gravity is needed. Forty-eight native English speakers without ESL teaching experience and 10 experienced ESL teachers evaluated a set of 18 timed, 30-minute essays written by high intermediate to advanced native-Chinese ELLs. Errors were identified, verified, tagged, and classified by the level of irritation they produced. Results show the most serious errors included count/non-count (C/NC), insert verb (INSERT V), omit verb (OMIT V), and subject-verb agreement (SV). The most frequent error type was word choice (WC), followed by singular/plural (S/PL), awkward (AWK), and word form (WF). When combined, singular/plural (S/PL), word form (WF), word choice (WC), and awkward (AWK) errors were found to be the most critical. These findings support Burt and Kiparsky's (1972) global/local error distinction in which global errors, or those lexical, grammatical and syntactic errors that affect the overall organization or meaning of the sentence (Burt, 1975) are deemed more grievous than local ones, which affect only "single elements (constituents)" (Burt, 1975, p. 57). Implications are discussed in terms of future research and possible uses in the Dynamic Written Corrective Feedback classroom.
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Cheng, Quan Jia. "A WLAN location estimation system using center of gravity as an algorithm selector." HKBU Institutional Repository, 2013. http://repository.hkbu.edu.hk/etd_ra/1513.
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Marchildon, Miguel. "An Application of the Gravity Model to International Trade in Narcotics." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37258.
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The transnational traffic of narcotics has had undeniable impacts on international development, for instance, stagnant economic growth in Myanmar (Chin, 2009), unsustainable agricultural practices in Yemen (Robins, 2016), and human security threats in Columbia (Thoumi, 2013). Furthermore, globalization is a catalyst for the transnational narcotics traffic (Robins, 2016; Aas, 2007; Kelly, Maghan & Serio, 2005). Several qualitative studies exist on the transnational narcotics traffic, yet few quantitative studies examine the issue. There is thus an opportunity for novel quantitative studies on the general question: “what are the main economic factors that influence the transnational traffic of narcotics between countries?” This study looked at the specific question: “are distance and economic size correlated with the volume of narcotics traffic between countries?” This study chose the gravity model as it centres on bilateral trade (Tinbergen, 1962), accounts for trade barriers (Kalirajan, 2008) and is empirically robust (Anderson 2011). This study defined a basic functional gravity model relating a proxy of the narcotics traffic to distance and economic size. Four augmented functional gravity models were also advanced to address omitted variable bias. The research was limited conceptually to cross sectional and pooled time series data. In addition, the data was also limited practically to a convenience sample of secondary data drawn from: the United Nations Office on Drugs and Crime’s (UNODC) (2016a) Individual Drug Seizures (IDS); the World Bank’s (2016) World Development Indicators; and the CEPII’s GeoDist (2016) datasets. This study used a novel “dosage” approach to unit standardization to overcome the challenge posed by the many measures and forms of narcotics. The study used the Poisson pseudo maximum likelihood (PPML) estimator as its estimations of the gravity model are consistent (Gourieroux et al., 1984), allow heteroscedasticity (Silva & Tenreyro, 2006) and avoid back transformation bias (Cox et al., 2008). The evidence analyzed in this study seem to indicate that the gravity model may not be applicable in its current form to the transnational narcotics traffic among countries that report drug seizures to the UNODC. However, the sampling method and the choice of proxy are likely to influence these findings. Moreover, the low explanatory power of the gravity model for the narcotics traffic, reflected in the values of the pseudo-R-squared coefficient of determination, indicates that other factors are at play. For instance, authors such as Asad and Harris (2003) and Thoumi (2003) argue that institutions could be a key factor in the narcotics traffic. Future empirical research into this topic could build on the theses findings to introduce new proxies and to explore alternate theoretical frameworks.
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Venkat, Ratnam Madineni, and Christoph Jacobi. "Study on stratospheric gravity wave activity: global and seasonal variations deduced from the CHAllenging Minisatellite Payload (CHAMP)-GPS Satellite." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 30 = Meteorologische Arbeiten aus Leipzig ; 8 (2003), S. 136-148, 2003. https://ul.qucosa.de/id/qucosa%3A15246.
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Global analyses of gravity wave activity in the stratosphere are presented for the first time using German Low Earth Orbit (LEO) satellite CHAMP. Temperature profiles obtained from CHAMP/GPS radio occultations are first compared with ground based instruments. In general, good agreement is found between these different techniques. Monthly mean Ep values of potential energy, Ep values, being a measure of gravity wave activity, which is estimated with radiosonde observations are compared with CHAMP/GPS data and found that radiosonde observed Ep values are higher than those estimated with radio occultations. There exists a strong diurnal variation of gravity wave activity. From the global morphology of gravity wave activity, large values Ep are noticed even at mid latitudes during winter months besides the tropical latitudes but not during equinoxes suggesting that wave activity, especially at stratospheric heights, is not only modulated due to orography (mountain/lee waves) but mainly depends on seasonal variations at respective latitudes. Latitudinal and vertical variation of gravity wave activity reveals the existence of large Ep values below 25 km and low values in between 25 and 30 km in all the seasons near equator. During southern hemisphere winter, large values are noticed. During equinoxes, these values are nearly same between northern and southern hemispheres (NH and SH) at mid-latitudes. During the months of solstices, Ep distribution involves a larger hemispheric asymmetry at middle and higher latitudes. Large values of Ep are noticed at SH polar latitudes during Sep-Oct months and the latitude range is wider (±300° latitude in both the hemispheres) with large Ep values in all the seasons except winter.Zum ersten Mal werden globale Analysen der Schwerewellenaktivität, bestimmt unter Verwendung des CHAMP LEO-Satelliten, vorgestellt. Temperaturprofile der CHAMP/RO-Okkultationen werden zunächst mit bodengestützten Messungen verglichen. Generell ist die Übereinstimmung gut. Monatliche Mittelwerte der potentiellen Energie Ep, die als Maß für Schwerewellenaktivität gilt, wurden aus Radisonden- und CHAMP-Messungen bestimmt, wobei die CHAMP-Daten höhere Werte lieferten. Es existiert eine deutlicher Tagesgang von Ep. Die globale Morphologie der Schwerewellenaktivität zeigt hohe Werte nicht nur am Äquator, sondern auch in mittleren Breiten, dies aber nicht während der Äquinoktien. Dies weist darauf hin, dass Schwerewelleaktivität nicht nur orographisch angetrieben ist, sondern in verschiedenen Breiten vom Jahresgang abhängt. Die Breiten- und Höhenabhängigkeit der Schwerewellenaktivität zeigt zwischen 25 und 30 km niedrige, unterhalb von 25 km hohe Werte von Ep am Äquator. Während des Winters in der Südhemisphäre sind die Werte hoch, während zu den Äquinoktien hohe Werte in mittleren Breiten beider Hemisphären zu finden sind. Während der Solstitien zeigt die Ep-Verteilung stärkere hemisphärische Asymmetrie. Hohe Werte von Ep werden während des südpolaren Frühjahrs gemessen. Der äquatoriale Bereich hoher Varianz ist in allen Jahreszeiten außer im Winter breit (±300°).
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Norin, Elvira. "Barnmorskors arbetsuppgifter mot gravida kvinnor : En intervjustudie om hur barnmorskor arbetar samt vilka frågor och funderingar kvinnorna har." Thesis, Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-27079.
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The purpose of the study is to investigate midwife's work towards pregnant women. The method of the study had a qualitative approach and the data collection was done using semistructured interviews. Three phoneinterviewes and an interview face to face. The method used had a qualitative approach and semi structured telephone interviews as well an interview with a personal meeting was the results implementation. The participants in the survey were four midwives recruited by telephone. The interviews were recorded, transcribed and analyzed with a manifest thematic content analysis, with a phenomenological element. The Result gave four different themes: The health call - a good foundation for maternity health care, trust and trust, diet and exercise, insufficient knowledge and midwives experience of support. The result showed that midwives work on the same guidelines, that is the BAS program. They felt short of time and wished that the visits with the women could be a bit more flexible. The conclusion is that more time for each visit would be necessary and that cooperation with other actors would make the work more efficient and fair.
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Rosat, Séverine. "Variations temporelles de la gravité en relation avec la dynamique interne de la Terre - Apport des gravimètres supraconducteurs." Phd thesis, Université Louis Pasteur - Strasbourg I, 2004. http://tel.archives-ouvertes.fr/tel-00144439.
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La dynamique et la structure interne de la Terre sont mal contraintes en profondeur, car les signaux induits en surface, de faible amplitude et basse fréquence, atteignent le seuil de détection des sismomètres. La gravimétrie devient un outil privilégié d'investigation de la Terre profonde aux longues périodes. Les variations temporelles de la gravité sont enregistrées en permanence par des gravimètres relatifs cryogéniques. Nous étudions les niveaux de bruit de ces stations sur un large spectre de fréquences allant des modes propres sismiques longue période jusqu'aux marées. Nous montrons que les gravimètres supraconducteurs apportent une contribution unique à l'étude des modes de vibration les plus graves qui échantillonnent la Terre de la surface jusqu'au noyau. Nous mettons en avant (1) l'éclatement dû à la rotation et à l'ellipticité du mode propre 0S2 en cinq singlets, (2) la première observation du mode sismique 2S1, après le séisme du Pérou du 23 juin 2001 de magnitude 8.4.Nous nous consacrons à la recherche du mode propre de translation de la graine 1S1 qui n'a jamais été observé sans ambiguïté. Sa détection est primordiale car elle permettrait de contraindre le saut de densité à l'interface graine - noyau liquide, ainsi que la viscosité à cette interface et la stratification du noyau fluide. Pour cela nous développons des méthodes de sommation, de détection automatique des signaux et une famille d'ondelettes.
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Ge, Shengjie. "GPS radio occultation and the role of atmospheric pressure on spaceborne gravity estimation over Antarctica." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149070384.
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Bedada, Tullu Besha. "Absolute geopotential height system for Ethiopia." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4726.
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This study used airborne gravity data, the 2008 Earth Gravity Model (EGM08) and Shuttle Radar Topographic Mission (SRTM) digital elevation data in a ‘Remove-Compute-Restore’ process to determine absolute vertical reference system for Ethiopia. This gives a geopotential height at any isolated field point where there is a Global Navigation Satellite System (GNSS) measurement without reference to a vertical network or a regional datum point. Previously, height was determined conventionally by connecting the desired field point physically to a nearby bench mark of a vertical network using co-located measurements of gravity and spirit levelling. With the use of precise GNSS positioning and a gravity model this method becomes obsolesce. The new approach uses the ‘Remove-Restore’ process to eliminate longer to shorter wavelengths from the measured gravity data using EGM08 and geometrical and condensed gravity models of the SRTM data. This provides small, smooth and localised residuals so that the interpolation and integration involved is reliable and the Stokes-like integral can be legitimately restricted to a spherical cap. A very fast, stable and accurate computational algorithm has been formulated by combining ‘hedgehog’ and ‘multipoint’ models in order to make tractable an unavoidably huge computational task required to remove the effects of about 1.5 billion! SRTM topographic mass elements representing Ethiopia and its immediate surroundings at 92433 point airborne gravity observations. The compute stage first uses an iterative Fast Fourier Transform (FFT) to predict residual gravity at aircraft height as a regular grid on to the surface of the ellipsoidal Earth and then it used a Fourier operation equivalent to Stokes’ integral to transform the localised gravity disturbance to residual potential. The restore process determines the geopotential number on or above the Earth’s surface where practitioners need it by restoring the potential effects of the removed masses. The accuracy of the geopotential number computed from gravity and topography was evaluated by comparing it with the one derived directly from EGM08 and precise geodetic levelling. The new model is in a good agreement across 100 km baseline with a standard deviation of 56 10−2 2 −2 × m s and 39 10−2 2 −2 × m s relative to EGM08 and levelling, respectively ( 10−2 2 −2 m s is approximately equivalent to 1mm of height). The new method provides an absolute geopotential height of a point on or above the Earth’s surface in a global sense by interpolating from geopotential models prepared as the digital grids carried in a chip for use with the GNSS receiver in the field.
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Rexer, Moritz [Verfasser], Christian [Akademischer Betreuer] [Gutachter] Hirt, Pavel [Gutachter] Novak, and Roland [Gutachter] Pail. "Spectral Solutions to the Topographic Potential in the context of High-Resolution Global Gravity Field Modelling / Moritz Rexer ; Gutachter: Pavel Novak, Christian Hirt, Roland Pail ; Betreuer: Christian Hirt." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1136422773/34.
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Lu, Biao [Verfasser], Frank [Akademischer Betreuer] Flechtner, Frank [Gutachter] Flechtner, Wolf-Dieter [Gutachter] Schuh, and Matthias [Gutachter] Becker. "Global and regional gravity field recovery by combining satellite, air-shipborne and terrestrial gravimetry data / Biao Lu ; Gutachter: Frank Flechtner, Wolf-Dieter Schuh, Matthias Becker ; Betreuer: Frank Flechtner." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1190717603/34.
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Rexer, Moritz Verfasser], Christian [Akademischer Betreuer] [Gutachter] Hirt, Pavel [Gutachter] Novak, and Roland [Gutachter] [Pail. "Spectral Solutions to the Topographic Potential in the context of High-Resolution Global Gravity Field Modelling / Moritz Rexer ; Gutachter: Pavel Novak, Christian Hirt, Roland Pail ; Betreuer: Christian Hirt." München : Universitätsbibliothek der TU München, 2017. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20170531-1349781-1-7.
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Silva, Geisiane Michelle da. "O impacto da crise financeira de 2008 sobre as exportações paranaenses: uma aplicação do modelo gravital." Universidade Estadual do Oeste do Parana, 2014. http://tede.unioeste.br:8080/tede/handle/tede/2153.
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The aim of this study was to analyze the impact of the 2008 financial crisis on Paraná´s exports through Gravity Model. The Gravity Equation estimated used as the dependent variable the exports of Paraná and as independent variables the Gross Domestic Product (GDP) and population of the state, GDP and population of importers countries of products from Paraná, the distance in kilometers between the state´s capital and the capital of the importer country, commodities prices in the international market, the area of importers countries and the dummies crisis, China, NAFTA, European Union and MERCOSUR. The Equation was estimated using panel data models by Pooled, Fixed Effects and Random Effects. The tests of Chow, Hausman and Breusch-Pagan LM indicated that the best model to be analyzed is the Random Effects. The tests of Breusch -Pagan and Wooldridge indicated, respectively, the presence of heteroscedasticity and autocorrelation. Thus, the Random Effects model was estimated with heteroscedasticity correction, with correction for autocorrelation and both fixes. According to the Equation estimated by the Random Effects model with heteroscedasticity and autocorrelation correction, the variables GDP and population of Paraná, GDP and population of importers countries and commodities prices were statistically significant and their coefficients showed, with the exception of the Paraná´s GDP, a positive relationship with the Paraná´s exports. The variables distance and area of importers countries were statistically insignificant and their coefficients showed an inverse relationship with exports of Paraná. The dummies China, NAFTA, European Union and MERCOSUR were statistically insignificant. Their coefficients showed a positive relationship between the Paraná´s exports and China and MERCOSUR and negative with NAFTA and the European Union. The dummy crisis was statistically significant, indicating that reduction in demand caused by the global financial crisis led to a reduction of 11,68% in Paraná´s exports. However, between 2008 and 2009, the Paraná´s exports fell by 26,3%. Thus, the occurrence of crisis partially explained the drop in exports of Paraná between 2008 and 2009. This can be explained by non-tariff barriers imposed by countries in response to the financial crisis.
O objetivo deste estudo foi analisar o impacto da crise financeira de 2008 nas exportações do Paraná através do Modelo Gravitacional. A Equação Gravitacional estimada utilizou como variável dependente as exportações do Paraná e como variáveis independentes o Produto Interno Bruto (PIB) e a população do estado, o PIB e a população dos países importadores de produtos paranaenses, a distância em quilômetros entre a capital do estado e a capital do país importador, o preço das commodities no mercado internacional, a área dos países importadores e as dummies crise, China, NAFTA, União Europeia e MERCOSUL. A Equação foi estimada por meio de dados em painel pelos modelos Pooled, de Efeitos Fixos e de Efeitos Aleatórios. Os testes de Chow, Hausman e LM de Breusch-Pagan indicaram que o melhor modelo a ser analisado é o de Efeitos Aleatórios. Os testes de Breusch-Pagan e de Wooldridge indicaram, respectivamente, a presença de heterocedasticidade e de autocorrelação. Assim, o modelo de Efeitos Aleatórios foi estimado com correção de heterocedasticidade, com correção de autocorrelação e com ambas as correções. De acordo com a Equação estimada pelo modelo de Efeitos Aleatórios com correção de heterocedasticidade e autocorrelação, as variáveis PIB e população paranaense, PIB e população dos países importadores e preço das commodities foram estatisticamente significativas e seus coeficientes indicaram, com exceção do PIB do Paraná, relação positiva com as exportações paranaenses. As variáveis distância e área dos países importadores foram estatisticamente insignificantes e seus coeficientes mostraram uma relação inversa com as exportações do Paraná. As dummies China, NAFTA, União Europeia e MERCOSUL foram estatisticamente insignificantes. Seus coeficientes indicaram relação positiva entre as exportações paranaenses e a China e o MERCOSUL e negativa com o NAFTA e a União Europeia. A dummy crise foi estatisticamente significativa, indicando que redução da demanda global ocasionada pela crise financeira acarretou redução de 11,68% nas exportações paranaenses. Entretanto, entre 2008 e 2009, as exportações paranaenses apresentaram queda de 26,3%. Assim, a ocorrência da crise explicou parcialmente a queda das exportações do Paraná entre 2008 e 2009. Isto pode ser justificado pelas barreiras não tarifárias impostas pelos países em resposta à crise financeira.
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Yaseen, Hafiz Muhammad. "Modélisation de l'infection par le chikungunya(CHIK), de son impact, et des facteurs pronostiques de chronicité et de qualité de vie post-CHIK." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5008.
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Afin de modéliser l'évolution de l’infection par le chikungunya (CHIK), son impact, et les facteurs pronostiques de chronicité, nous avons travaillé en trois parties. L'impact à long terme de l’épidémie de CHIK en 2005-2006 à la Réunion a été estimé en calculant la proportion de patients en phase chronique au cours du temps et la charge globale de morbidité du CHIK par la méthode des années de vie ajustées sur l'invalidité (méthode DALY de l’OMS, qui prend en compte les années de vie perdues en raison de la mortalité prématurée et des années de vie vécues avec une incapacité). Ainsi entre 51,2 et 65,3% des patients étaient estimés symptomatiques après 1 an et 0% à15,2% après 5 ans. Le total d’années de vie en bonne santé perdues à la Réunion a été estimé à 65-73/1000 personnes, 55,5% des pertes concernant la population active (les 20 à 60 ans), et 86% étant dues à la persistance de rhumatismes post-CHIK (phase chronique). Les facteurs pronostiques de la persistance de rhumatismes et de l’altération de la qualité de vie (QdV) à long terme (30 mois) ont été étudiés dans une cohorte des gendarmes dont 25% étaient infectés (CHIK+). Etre CHIK+, avoir des comorbidités et un moral déprimé pendant la phase aiguë étaient prédictifs de la persistance d’arthrite comme d’arthralgies. De plus, la présence d’arthralgies ou arthrite à six mois était très prédictive de la persistance des mêmes rhumatismes à 30 moisTo model the evolution of chikungunya virus (CHIK) infection, its impact and the prognostic factors of post-CHIK rheumatism and quality of life, we worked in three parts. The long-term impact of the 2005-2006 CHIK outbreaks in Reunion Island was estimated by calculating the proportion of chronic patients over time and the global burden of CHIK using the Disability Adjusted Life Years (DALY) method. This method sums the years of life lost due to premature mortality and the years lived with disability. Between 51.2 and 65.3% of patients were estimated chronic after 1 year and 0%-15.2% after 5 years. The global disease burden of CHIK was estimated 65-73 DALYs/1000 persons, 55.5% concerning the active population (20-60 years old), and 86% due to persistence of post-CHIK rheumatisms. Prognostic factors of the long-term (30 months) rheumatisms and impaired quality of life (QoL) were studied in a cohort of French army policemen (25% CHIK infected: CHIK+). Being CHIK+, suffering of comorbidity and having depressed mood during the acute stage were predictive for both persistent arthritis and arthralgias at 30 months. In addition, suffering of either arthralgias or arthritis at six months was predictive of the same symptoms at 30 months. Determinants of impaired QoL were CHIK infection and comorbidity, in addition to older age, work-stoppage during the acute infection and arthritis at 6 months for the QoL physical component, and depressed mood at 6 months for the mental health component.Association between the severity of initial CHIK-stages and recovery were studied using multiple correspondence analysis (MCA)
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Perosanz, Félix. "Utilisation des mesures GPS pour la restitution dynamique précise d'orbites et l'amélioration des modèles globaux de champ de gravité terrestre : application au satellite TOPEX/POSEIDON et à la simulation des performances des futures missions géodésiques." Toulouse 3, 1995. http://www.theses.fr/1995TOU30183.
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La determination de modeles de champ de gravite terrestre est une activite essentielle du groupe de recherches de geodesie spatiale (grgs) depuis plus de 20 ans. Chaque nouvelle iteration de la serie des modeles grim a apporte des ameliorations sensibles de la description du geopotentiel tant en resolution qu'en precision. Cependant pour differentes applications geophysiques et oceanographiques la qualite de ces modeles apparait d'ores et deja comme limitative. Un gain d'un ordre de grandeur sur la connaissance du geoide doit etre realise dans un proche avenir. La communaute scientifique s'accorde a penser qu'un tel progres ne pourra venir que d'une nouvelle mission satellitaire mettant en uvre les techniques de poursuite de satellite par satellite (sst) et/ou de gravimetrie embarque (sgg) a une altitude inferieure a 500 km. Le satellite topex/poseidon (t/p), lance en 1992 sur une orbite a 1300 km d'altitude, embarquait a titre probatoire et pour la premiere fois dans de bonnes conditions de suivi, un recepteur gps de grande qualite. Des mesures radioelectriques de precision centimetrique entre l'ensemble des 24 satellites de la constellation gps orbitants a 20000 km d'altitude et t/p allaient etre possible. L'orbitographie operationnelle du satellite etait assuree par les systemes de poursuites doris et laser dont les performances etaient reconnues. De gravite. Dans un premier temps les travaux de these ont consiste a etendre les capacites du logiciel de calcul d'orbites gins du grgs au traitement des mesures gps. Cela a implique le developpement complet de la chaine de pre-traitement de ces mesures, l'introduction de la fonction de mesure gps (double difference de phase) et la gestion des inconnues associees dans gins ainsi que sa reorganisation pour en faire un outil d'orbitographie multi-satellites. L'ensemble des mesures gps, doris et laser mettant en uvre le satellite t/p, 20 satellites gps, 20 stations gps du reseau igs et l'ensemble des stations des reseaux doris et laser sur une periode de 10 jours (cycle 15 de t/p) ont ete traitees. Differents tests ont montre une precision de restitution de l'orbite de t/p de 3-4 cm dans la direction radiale et decimetrique dans les trois directions (rms), soit des performances comparables a celles obtenues par d'autres groupes (jet propulsion laboratory, university of texas). De plus les differentes combinaisons des trois types d'observables ont montre une amelioration de la restitution de l'orbite de t/p faible mais systematique lorsque les mesures gps et doris sont traitees simultanement. Enfin, les systemes d'equations normales issus du traitement des mesures gps, doris et laser sur l'ensemble du cycle 15 ont ete generees et combinees pour donner 5 modeles de champ de gravite. Une etude relative de ces differentes solutions a montre d'une part, q ue les donnees gps avaient l'impact le plus important sur les modeles et d'autre part, que les solutions incluant les equations normales (gps+doris) et (gps+doris+laser) donnaient les meilleurs resultats suggerant une certaine complementarite au sens dynamique de ces differents systemes de poursuite. Dans un second temps, le developpement d'un logiciel de simulation des performances de mission geodesique a ete entrepris. En effet, depuis l'abandon du projet aristoteles en 1991, differents projets dediees a l'amelioration des modeles de champ de gravite ont ete proposees (step, games, grace). La variete des techniques mises en uvres (sst ou sgg), des caracteristiques instrumentales (type d'observation, precision, bruit) et orbitales (altitude entre 200 et 500 km) necessitaient le developpement d'un logiciel de simulation a la fois general et rapide. Cet outil, baptise manege (methode analytico-numerique d'estimation du geopotentiel), a permis d'effectuer une etude comparative des performances de chacun de ces projets ainsi que de contribuer a la definition du concept bridge du cnes
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Betlach, František. "Studie napjatosti a přetvoření zděné přehrady." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240016.
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The Diploma thesis deals with the assessment of global and local stability of the masonry gravity dam Pastviny, for two load conditions. The first part consists of a present state review describing selected masonry dams in the Czech Republic and abroad. Further on a conceptual and mathematical formulation of the seepage flow and strain-stress problem are stated. The case study is focused on the practical application of formulated problems on the Pastviny dam. Firstly the available data have been assembled and processed. Global and local safety of the dam was assessed for the selected most vulnerable profile of the dam body. In the final chapters 5, 6 and 7, the seepage flow, stress and strain have been calculated and graphically displayed. Finally global and local stability have been assessed and completed with final summary of the results and concluding remarks.
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Julié, Félix-Louis. "Sur le problème à deux corps et le rayonnement gravitationnel en théories scalaire-tenseur et Einstein-Maxwell-dilaton." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC131/document.
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Avec la naissance de l’"astronomie gravitationnelle", vient l’opportunité inédite de tester la relativité générale et ses alternatives dans un régime de champ fort jamais observé jusqu’alors : celui de la coalescence d’un système binaire d’objets compacts. Cette thèse propose d’étudier le problème du mouvement ainsi que du rayonnement gravitationnel d’un tel système en gravités modifiées, en y adaptant et en généralisant certains développements analytiques clés de la relativité générale. On montre d’abord comment étendre le formalisme "effective-one-body" (EOB) à une large classe de gravités modifiées, parmi lesquelles les théories scalaire-tenseur. Dans ces dernières, l’interaction gravitationnelle est modifiée par l’ajout d’un degré de liberté scalaire (sans masse) à la relativité générale. Le lagrangien à deux corps correspondant étant connu à l’ordre post-post-keplerien, nous construisons un hamiltonien EOB associé, décrivant le mouvement d’une particule test dans des champs effectifs. Ceci permet de simplifier la dynamique à deux corps et d’en définir une resommation ; et ainsi, d’en explorer le régime de champ fort, près de la coalescence du système. On "s’attaque" ensuite, et pour la première fois, à la description analytique d’un système binaire de trous noirs "chevelus", afin d’obtenir les formes d’ondes gravitationnelles (EOB) associées ; et ce, sur l’exemple simple des théories Einstein-Maxwell-dilaton, qui généralisent les théories scalaire-tenseur par l’ajout d’un champ vectoriel (sans masse). Pour ce faire, on calcule le lagrangien à deux corps à l’ordre post-keplerien ainsi que le flux d’énergie rayonnée à l’infini à l’ordre quadrupolaire. Tout comme en relativité générale, ces développements reposent sur la description de la trajectoire des trous noirs par les lignes d’univers de particules ponctuelles, décrites par une action "skeleton" généralisant celle, géodésique, de la relativité générale. Enfin, à l’aide des "superpotentiels" de Katz, que l’on généralise pour définir la masse (nœtherienne) d’un trou noir à "cheveux" vectoriel et scalaire, on montre que la première loi de la thermodynamique qui en découle est particulièrement adaptée, lorsqu’un trou noir est membre d’un système binaire, pour en décrire les réajustements éventuels sous l’influence d’un compagnon lointain. La thermodynamique des trous noirs est alors utilisée pour interpréter et discuter du domaine de validité de leur "skeletonisation"With the birth of "gravitational wave astronomy" comes the opportunity to test general relativity and its alternatives in a strong field regime that had never been observed so far: that of the coalescence of a compact binary sytem. This thesis studies the problem of motion and gravitational radiation from such systems in modified gravities, by adapting some of the key analytical tools that were first developed in the context of general relativity. First, we show how to widen the "effective-one-body" (EOB) formalism to a large class of modified gravities, including, e.g., scalar-tensor theories. In the latter, the gravitational interaction is described by supplementing general relativity with a (massless) scalar degree of freedom. The corresponding two-body lagrangian being known at post-post-keplerian order, we build an associated EOB hamiltonian, which describes the motion of a test particle orbiting in effective external fields. This enables to simplify and resum the two-body dynamics; and hence, to explore the strong-field regime near merger. We then "tackle", for the first time, the analytical description of "hairy" binary black hole systems, and obtain their (EOB) gravitational waveform counterparts in Einstein-Maxwell-dilaton theories, which generalize scalar-tensor theories by means of a (massless) vector field. To that end, we derive the two-body lagrangian at post-keplerian order as well as the energy flux radiated at infinity at quadrupolar order. As in general relativity, our developments rely on the phenomenological description of the black hole’s trajectories as worldlines of point particles that are, in turn, described by a "skeleton" action generalizing that of general relativity. Finally, we develop a formalism based on Katz’ "superpotentials" to define the mass (as a nœther charge) of a black hole that is endowed with vector and scalar "hair". We then deduce the first law of thermodynamics, which is particularly suitable to describe its readjustments when interacting with a faraway companion. Black hole thermodynamics is lastly shown to be a powerful tool to interpret and discuss the scope of their "skeletonization"
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Yang, Qian. "Applications of Satellite Geodesy in Environmental and Climate Change." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6440.
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Satellite geodesy plays an important role in earth observation. This dissertation presents three applications of satellite geodesy in environmental and climate change. Three satellite geodesy techniques are used: high-precision Global Positioning System (GPS), the Gravity Recovery and Climate Experiment (GRACE) and Interferometric Synthetic Aperture Radar (InSAR). In the first study, I use coastal uplift observed by GPS to study the annual changes in mass loss of the Greenland ice sheet. The data show both spatial and temporal variations of coastal ice mass loss and suggest that a combination of warm atmospheric and oceanic condition drove these variations. In the second study, I use GRACE monthly gravity change estimates to constrain recent freshwater flux from Greenland. The data show that Arctic freshwater flux started to increase rapidly in the mid-late 1990s, coincident with a decrease in the formation of dense Labrador Sea Water, a key component of the deep southward return flow od the Atlantic Meridional Overturning Circulation (AMOC). Recent freshening of the polar oceans may be reducing formation of Labrador Sea Water and hence may be weakening the AMOC. In the third study, I use InSAR to monitor ground deformation caused by CO2 injection at an enhanced oil recovery site in west Texas. Carbon capture and storage can reduce CO2 emitted from power plants, and is a promising way to mitigate anthropogenic warming. From 2007 to 2011, ~24 million tons of CO2 were sequestered in this field, causing up to 10 MPa pressure buildup in a reservoir at depth, and surface uplift up to 10 cm. This study suggests that surface displacement observed by InSAR is a cost-effective way to estimate reservoir pressure change and monitor the fate of injected fluids at waste disposal and CO2 injection sites.
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Deville, Sabrina. "Caractérisation de la zone non saturée des karsts par la gravimétrie et l'hydrogéologie." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-00829346.
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Les aquifères karstiques constituent l'essentiel des ressources en eau du pourtour Méditerranéen. Au-delà de la zone saturée de ces systèmes, la zone non saturée constitue une entité importante quant au transfert et au stockage temporaire de l'eau. La structure et le fonctionnement de cette entité du karst sont complexes et mal connus à cause du processus de karstification qui hiérarchise la circulation hydrodynamique en son sein. Dans cette étude nous utilisons des méthodes géodésiques et hydrogéologiques afin d'observer de façon directe et de quantifier les processus de transfert et de stockage de la zone non saturée. Les mesures gravimétriques en surface et profondeur sur différents systèmes karstiques ont permis de quantifier les variations du stockage en eau saisonnier dans la zone non saturée. La gravimétrie différentielle montre que ces variations sont réparties dans les quelques premiers mètres de la zone non saturée. Il semble, de plus, que la capacité de stockage de la zone non saturée soit fonction de la lithologie de l'encaissant (calcaire et dolomie). Enfin, des observations directes du flux d'eau en zone non saturée ont été effectuées par le biais de mesures dans différentes cavités. Nous montrons que certaines caractéristiques du flux d'eau en zone non saturée, comme la présence d'un flux bipolaire lent-rapide, peuvent être généralisées quelque soit la profondeur de mesure et la surface d'impluvium. La modélisation de ce flux, à partir d'un schéma simple, a montré la complexité des processus de transfert engendrés au sein de la zone non saturée.
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Larson, Susan K. "The Origins of Four Paterae of Malea Planum, Mars." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1736.pdf.
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Brunswic, Léo. "Surfaces de Cauchy polyédrales des espaces temps plats singuliers." Thesis, Avignon, 2017. http://www.theses.fr/2017AVIG0420/document.
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L'étude des espaces-temps plats singuliers munis d'une surface de Cauchy polyédrale est motivée par leur rôle de model jouet de gravité quantique proposé par Deser, Jackiw et 'T Hooft. Cette thèse porte sur les paramétrisations de certaines classes d'espaces-temps plat singuliers : les espaces-temps plats avec particules massives et BTZ Cauchy-compacts maximaux. Deux paramétrisations sont proposées, l'une reposant sur une extension du théorème de Mess aux espaces-temps plats avec BTZ et la surface de Penner-Epstein, l'autre reposant sur une généralisation du théorème d'Alexandrov aux espaces-temps plats avec particules massives et BTZ. Ce travail propose également une amorce de cadre théorique permettant de considérer des espaces-temps singuliers plus générauxThe study of singular flat spacetimes with polyhedral Cauchy-surfaces is motivated by the quantum gravity toy model role they play in the seminal work of Deser, Jackiw and 'T Hooft. This thesis study parametrisations of classes of singular flat spacetimes : Cauchy-compact maximal flat spacetimes with massive and BTZ-like singularities. Two parametrisations are constructed. The first is based on an extension of Mess theorem to flat spacetimes with BTZ and Penner-Epstein convex hull construction. The second is based on a generalisation of Alexandrov polyhedron theorem to radiant Cauchy-compact flat spacetimes with massive and BTZ-like singularities. This work also initiate a wider theoretical background that encompass singular spacetimes
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Chu, Yun-Wen, and 朱韻雯. "Entrepreneurship and Global Capital Flows: A Gravity Model Approach." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2jbp64.
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博士國立政治大學
國家發展研究所
106
Entrepreneurs allocate resources based on market-driven forces. The entrepreneurship takes on different features and forms varying with the conditions of different social, cultural and economic context, and it gradually becomes the vital element for global economic development. This research is based on the national bilateral panel data of global securities and direct investment from the year 2003 to 2015, and it uses the Gravity Model to explore the entrepreneurship factors, such as social values, individual attributes and entrepreneurial activity, that had taken shape in different countries or under different economic entities. In terms of research method, Ordinary Least Squares and Panel Data Modal is used. The primary empirical result shows that the entrepreneurship factors have significant impact on capital flows generated from sources such as securities investment or direct investment. In other words, entrepreneurship has the effect of attracting capital flows. This research also proposes that the government shall consider the nature of policy objectives or the length of duration when making strategies or policies in stimulating entrepreneurship so as to attract appropriate capital forms.
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徐欣瑩. "Improved Determinations of Global Gravity Anomaly Model and Shallow-Water Gravity Anomalies from Multi-Satellite Altimetry." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86569664011620298902.
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Lan, Chien-jung, and 藍健榕. "The Analysis of Global Transportation Service: The Analysis of Global Transportation Service:The Gravity Model Approach." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/99874406052906515948.
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碩士國立臺灣科技大學
企業管理系
97
This study focuses on the determinants of global transportation service trade between countries and regions. Using the augmented gravity model, our main result showed as fallows. First, the effect of economic size to transportation of import country service demand is greater than those of export countries. This implies that the global transportation service is pulling by demand ride rather than by supply ride. Secondly, total value of service industries has significant positive effort to international transportation service. Finally, the depreciation of Asian currencies positively increase Asian countries its transportation services export. However, the elasticity of relative exchange rate is insensitive for Europe transportation services export.
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Jang, Rung-Jie, and 張榮傑. "Altimeter data processing for improved determination of global marine gravity." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/17435816462628299316.
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碩士國立交通大學
土木工程系
89
The altimeter database at the National Chiao Tung University, which includes data from Seasat, Geosat, ERS-1, ERS-2 and TOPEX/POSEIDON missions, is updated in this study in an attempt to derive marine gravity with an improved accuracy. The old Geosat/ERM and Geosat/GM are replaced by the JGM3 GDRS, which use better geophysical correction models compared to the previous version. For the tide model except for Seasat and T/P, the NAO99b model is used. A new method is used to remove outliers and compute averaged sea surface heights for the repeat missions. A more rigorous method of assigning standard deviations to the non-repeat missions is studied, but we conclude that an empirical standard deviation for each of the non-repeat mission will yield a better agreement between computed gravity anomalies and shipborne values. The optimum filter wavelengths for the altimeter data for the non-repeat missions are also empirically determined. Finally the inverse Vening Meinesz formula with the 1D FFT technique is used to compute gravity anomalies at 12 areas in the world ocean. Gridding of north and east components is done by least-squares collocation. On average the accuracy of the derived marine gravity anomalies is improved by 0.77 mgal compared to those of Hwang et al. (1998).
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Ali, Ibraheem F. M. "A globally consistent and dynamic Canadian gravity reference frame for a modern heighting system and other applications /." 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19735.
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Thesis (M.Sc.)--York University, 2006. Graduate Programme in Earth and Space Science.Typescript. Includes bibliographical references (leaves 97-101). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19735
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Thompson, Paul Frank. "Interpreting the Earth's time varying geopotential as observed from space and comparisons to global models of hydrologic transport." Thesis, 2004. http://hdl.handle.net/2152/1420.
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Thompson, Paul Frank Tapley Byron D. "Interpreting the Earth's time varying geopotential as observed from space and comparisons to global models of hydrologic transport." 2004. http://repositories.lib.utexas.edu/bitstream/handle/2152/1420/thompsonp86692.pdf.
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Kao, Eu-Chi, and 高豫麒. "Global marine gravity anomalies from Seasat, Geosat, ERS-1 , TOPEX/POSEIDON Satellite altimetry." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/45424798899045138694.
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碩士國立交通大學
土木工程研究所
85
Global marine gravity anomalie at a 2''×2'' grid have been determined from Seasat, Geosat, ERS-1 and TOPEX/POSEIDON altimeter data. The inverse Vening Meinesz formula with an 1D FFT method was used to compute gravity anomalies from gridded north-south and west-east geoid gradients, in a remove-restore procedure with the EGM96 gravity model as the reference field. The data cover the area 72°S to 72°N in latitude and 0° to 360° in iongitude. In the 12 test areas where ship gravity and satellite-derived gravity were compared, rms agreenents of 6-10 mgals were obtained and the gravity anomalies derived in this work are 0.5 mgal on average better than those derived by Sandwell and Smith (1997). The gravity anomalies are located at an ftp site (ftp://gps. cv.nctu.edu.tw) where an application grogram is available for extracting data in a subarea.
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Lin, Kuen-Feng, and 林崑峯. "The determinant factor of global migration flows：the application of gravity model and trade networks analysis." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/59361362871069705272.
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碩士世新大學
財務金融學研究所(含碩專班)
99
In recent years, a substantial increase in international migration of population. According to the latest statistical data of DESA (United Nations Department of Economic and Social Affairs), it will increase to more 200 million people that were the total number of the world population of 3.1% in 2010. Total fertility rate of Taiwan is 1.03% that was the last ranking of the world in 2009. Taiwan could refer to foreign experience “international migration”, and it an important strategy to solve the population problem. Before attract the international immigration, this study analyze the determinant factor driver of global migration. This research use global bilateral migration data of 226 countries and 51076 samples. Also use the indicators of communications networks to demonstrate international migration by gravity model and measure determinant factors of international migration. Base on the theory and model of the Population Econometrics, this study examine the determinant factors of international population migration by the gravity model. Also, this research use social networks analysis to examine the positive and negative determinant factors of international population movement. The results indicate that the geographical and cultural factors, social and economic factors, and international trade factors with the application of gravity model and social networks analysis are significant impact on the international population migration. In the application of social networks analysis, trade centre networks and communications networks of the indicators in the global population migration play an important role.
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Wang, Wei-Lung, and 王偉龍. "Shipborne gravity estimation from the combination of inertial measurement unit(IMU) and global positioning system (GPS)." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/08080784284787717959.
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碩士國立中興大學
水土保持學系所
102
The study is aimed at gravity estimation by using Inertial Measurement Unit(IMU) and Global Positioning System(GPS) data, and the accuracies of results are rigorously analyzed. The IMU and GPS data are from the proposal 「Shipborne gravity survey over the inshore areas of Taiwan」 sponsored by National Land Surveying and Mapping Center (NLSC) in 2011. In the step of data pre-processing, we consider different filter techniques and widths to determine a best filter combination according to the correlation coefficients and standard deviations between GPS and IMU data. Gaussian filter is adopted again to eliminate data noises in the step of gravity computation. The results are evaluated both by ZLS ship-derived and by EGM08-derived gravity. We conclude that (1) Gaussian and Cosine arch filters both exhibit more excellent results than others. (2) In Route 0514c, the best correlation coefficient 0.88 are occurred when the Gaussian filter widths use 5.5 s for IMU, and 2 s for GPS. (3) In Route 0519a, the best correlation coefficient 0.88 are occurred when the Gaussian filter widths use 5.0 and 1 s for IMU and GPS, respectively. (4) Route 2-2 show the best result that the accuracies reach 40 ? 50 mgal at Gaussian filter widths 200 ? 500s, and reach 20 ? 30 mgal at 1000 ? 1500 s.
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"Development of a small university satellite for performing a global survey of gravity waves in the mesosphere." UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN, 2009. http://pqdtopen.proquest.com/#viewpdf?dispub=3347577.
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