To see the other types of publications on this topic, follow the link: Gravity changes.
Dissertations / Theses on the topic 'Gravity changes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Gravity changes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Setiawan, Ari. "Modeling of Gravity Changes on Merapi Volcano." Phd thesis, [S.l. : s.n.], 2003. https://tuprints.ulb.tu-darmstadt.de/362/17/cv.pdf.
Full textAbstract:
Merapi volcano, located in Central Java, is one of the most active volcanoes in Indonesia. 2 million people are living in its immediate neighborhood. Therefore Merapi was selected within the International Decade of Natural Disaster Reduction (IDNDR) of UNESCO as one of 15 so called high risk volcanoes in the world. National and International research groups from Indonesia, France, Netherlands, Japan, USA and Germany are working on Merapi. Different methods are applied on Merapi to study the volcanic processes and to improve the possibilities to predict future eruptions. In this thesis the importance of gravity changes in space and time for the analysis of volcanic processes is analyzed and further developed. First the basic theory of Earth's gravity field and gravity anomalies is described. For the interpretation of gravity anomalies several programs have been developed using the MATLAB software package. The programs are used for the interpretation of gravity changes in time which have been observed five times between summer 1997 and summer 2000 in a repetition network around Merapi volcano. This network consists of 23 stations. During all campaigns four LaCoste&Romberg gravimeters model G and D have been used. Height changes at the observation sites are controlled by GPS-observations which have been carried out in parallel with the gravity measurements. The observed gravity and height changes are small. They reveal that Merapi volcano is just now an open system where no large stresses can build up. Nevertheless possible models are developed to explain the observed changes. Based on four geometric models of magma chamber and conduit within the volcano?s edifice as found in the literature the migration of magma in the conduit is investigated. The conduit system thereby is modeled by a cylinder, the magma chamber by a sphere. It is shown, that gravity changes map the migration of the magma, if gravity changes at stations at the crater rim are considered. Gravity changes at stations far away from the volcano conduit (2 ? 25 km) can be explained by changes within the geohydrothermal system. For this purpose particular ground water layers as determined by other geophysical methods (resistivity observations, magnetotelluric measurements and LOTEM) are modeled as concentric cylinders around the conduit of Merapi volcano. The resulting density changes in the cylinders explain with sufficient accuracy the observed gravity changes. Precise repeated gravity observations in combination with other geophysical methods allow therefore the detailed analysis of subsurface mass migration within a volcano.
2
Doi, Koichiro. "Study on Gravity Changes Induced by Atmospheric Loading." 京都大学 (Kyoto University), 1992. http://hdl.handle.net/2433/168819.
Full textAbstract:
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第4973号
理博第1370号
新制||理||765(附属図書館)
UT51-92-J20
京都大学大学院理学研究科地球物理学専攻
(主査)教授 中川 一郎, 教授 田中 寅夫, 教授 住友 則彦
学位規則第4条第1項該当
3
Anjasmara, Ira Mutiara. "Validating methods to infer mass changes from satellite gravity measurements using Synthetic Earth Gravity Modelling." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/2379.
Full textAbstract:
Leakage properties of isotropic and anisotropic filters used to recover mass changes from space gravity observations are studied. These are done through the use of gravity induced by simulated mass changes within a closed-loop validation procedure. Results show that the use of filter techniques can introduce significant errors introducing distortions between recovered and simulated mass. Previously not well known, the study revealed that leakage is dependent on the geographic location if the mass change considered.
4
Takada, Hiroki, Yoshiyuki Kitaoka, Satoshi Iwase, Yuuki Shimizu, Tomoyuki Watanabe, Meiho Nakayama, Masaru Miyao, and Koshin Mihashi. "Characteristic Changes of Sway of Center of Gravity with Advancing Afe." Research Institute of Environmental Medicine, Nagoya University, 2003. http://hdl.handle.net/2237/7608.
Full text
5
Morrow, Eric. "Estimates of Land Ice Changes from Sea Level and Gravity Observations." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11385.
Full textAbstract:
Understanding how global ice volume on the Earth has changed is of significant importance to improving our understanding of the climate system. Fortunately, the geographically unique perturbations in sea level that result from rapid changes in the mass of, otherwise difficult to measure, land-ice reservoirs can be used to infer the sources and magnitude of melt water. We explore the history of land-ice mass changes through the effect that these mass fluxes have had on both global and regional gravity and sea-level fields.Earth and Planetary Sciences
6
Cadwell, John Andres Jr. "Control of Longitudinal Pitch Rate as Aircraft Center of Gravity Changes." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/426.
Full textAbstract:
In order for an aircraft to remain in stable flight, the center of gravity (CG) of an aircraft must be located in front of the center of lift (CL). As the center of gravity moves rearward, pitch stability decreases and the sensitivity to control input increases. This increase in sensitivity is known as pitch gain variance. Minimizing the pitch gain variance results in an aircraft with consistent handling characteristics across a broad range of center of gravity locations.
This thesis focuses on the development and testing of an open loop computer simulation model and a closed loop control system to minimize pitch axis gain variation as center of gravity changes. DATCOM and MatLab are used to generate the open loop aircraft flight model; then a closed loop PD (proportional-derivate) controller is designed based on Ziegler-Nichols closed loop tuning methods. Computer simulation results show that the open loop control system exhibited unacceptable pitch gain variance, and that the closed loop control system not only minimizes gain variance, but also stabilizes the aircraft in all test cases. The controller is also implemented in a Scorpio Miss 2 radio controlled aircraft using an onboard microprocessor. Flight testing shows that performance is satisfactory.
7
Marriott, A. D. "'Appropriately related changes' : the meaning of narrative in Thomas Pynchon's 'Gravity Rainbow'." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356712.
Full text
8
Borden, Emily C. "The Relationship and Seasonal Changes of Hydration Measures in Collegiate Wrestlers." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523430813791537.
Full text
9
Vassalli, Melissa <1977>. "Numerical simulations of magma chamber dynamics at Campi Flegrei, and associated seismicity, deformation and gravity changes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/986/1/Tesi_Vassalli_Melissa.pdf.
Full textAbstract:
Understanding the complex relationships between quantities measured
by volcanic monitoring network and shallow magma processes is a crucial
headway for the comprehension of volcanic processes and a more realistic
evaluation of the associated hazard. This question is very relevant at Campi
Flegrei, a volcanic quiescent caldera immediately north-west of Napoli (Italy).
The system activity shows a high fumarole release and periodic ground slow
movement (bradyseism) with high seismicity. This activity, with the high
people density and the presence of military and industrial buildings, makes
Campi Flegrei one of the areas with higher volcanic hazard in the world.
In such a context my thesis has been focused on magma dynamics due
to the refilling of shallow magma chambers, and on the geophysical signals
detectable by seismic, deformative and gravimetric monitoring networks that
are associated with this phenomenologies. Indeed, the refilling of magma
chambers is a process frequently occurring just before a volcanic eruption;
therefore, the faculty of identifying this dynamics by means of recorded signal
analysis is important to evaluate the short term volcanic hazard.
The space-time evolution of dynamics due to injection of new magma
in the magma chamber has been studied performing numerical simulations
with, and implementing additional features in, the code GALES (Longo et al.,
2006), recently developed and still on the upgrade at the Istituto Nazionale di
Geofisica e Vulcanologia in Pisa (Italy). GALES is a finite element code based
on a physico-mathematical two dimensional, transient model able to treat
fluids as multiphase homogeneous mixtures, compressible to incompressible.
The fundamental equations of mass, momentum and energy balance
are discretised both in time and space using the Galerkin Least-Squares and
discontinuity-capturing stabilisation technique. The physical properties of
the mixture are computed as a function of local conditions of magma composition,
pressure and temperature.The model features enable to study a broad
range of phenomenologies characterizing pre and sin-eruptive magma dynamics
in a wide domain from the volcanic crater to deep magma feeding
zones.
The study of displacement field associated with the simulated fluid dynamics
has been carried out with a numerical code developed by the Geophysical
group at the University College Dublin (O’Brien and Bean, 2004b),
with whom we started a very profitable collaboration. In this code, the seismic
wave propagation in heterogeneous media with free surface (e.g. the
Earth’s surface) is simulated using a discrete elastic lattice where particle interactions
are controlled by the Hooke’s law. This method allows to consider
medium heterogeneities and complex topography.
The initial and boundary conditions for the simulations have been defined
within a coordinate project (INGV-DPC 2004-06 V3_2 “Research on active
volcanoes, precursors, scenarios, hazard and risk - Campi Flegrei”), to which
this thesis contributes, and many researchers experienced on Campi Flegrei
in volcanological, seismic, petrological, geochemical fields, etc. collaborate.
Numerical simulations of magma and rock dynamis have been coupled as
described in the thesis.
The first part of the thesis consists of a parametric study aimed at understanding
the eect of the presence in magma of carbon dioxide in magma in
the convection dynamics. Indeed, the presence of this volatile was relevant
in many Campi Flegrei eruptions, including some eruptions commonly considered
as reference for a future activity of this volcano. A set of simulations
considering an elliptical magma chamber, compositionally uniform, refilled
from below by a magma with volatile content equal or dierent from that
of the resident magma has been performed. To do this, a multicomponent
non-ideal magma saturation model (Papale et al., 2006) that considers the
simultaneous presence of CO2 and H2O, has been implemented in GALES.
Results show that the presence of CO2 in the incoming magma increases its
buoyancy force promoting convection ad mixing. The simulated dynamics
produce pressure transients with frequency and amplitude in the sensitivity
range of modern geophysical monitoring networks such as the one installed
at Campi Flegrei .
In the second part, simulations more related with the Campi Flegrei volcanic
system have been performed. The simulated system has been defined
on the basis of conditions consistent with the bulk of knowledge of Campi
Flegrei and in particular of the Agnano-Monte Spina eruption (4100 B.P.),
commonly considered as reference for a future high intensity eruption in this
area. The magmatic system has been modelled as a long dyke refilling a small shallow magma chamber; magmas with trachytic and phonolitic composition
and variable volatile content of H2O and CO2 have been considered. The
simulations have been carried out changing the condition of magma injection,
the system configuration (magma chamber geometry, dyke size) and the resident
and refilling magma composition and volatile content, in order to study
the influence of these factors on the simulated dynamics. Simulation results
allow to follow each step of the gas-rich magma ascent in the denser magma,
highlighting the details of magma convection and mixing. In particular, the
presence of more CO2 in the deep magma results in more ecient and faster
dynamics. Through this simulations the variation of the gravimetric field has
been determined.
Afterward, the space-time distribution of stress resulting from numerical
simulations have been used as boundary conditions for the simulations of
the displacement field imposed by the magmatic dynamics on rocks. The
properties of the simulated domain (rock density, P and S wave velocities)
have been based on data from literature on active and passive tomographic
experiments, obtained through a collaboration with A. Zollo at the Dept. of
Physics of the Federici II Univeristy in Napoli. The elasto-dynamics simulations
allow to determine the variations of the space-time distribution of
deformation and the seismic signal associated with the studied magmatic dynamics.
In particular, results show that these dynamics induce deformations
similar to those measured at Campi Flegrei and seismic signals with energies
concentrated on the typical frequency bands observed in volcanic areas.
The present work shows that an approach based on the solution of equations
describing the physics of processes within a magmatic fluid and the
surrounding rock system is able to recognise and describe the relationships
between geophysical signals detectable on the surface and deep magma dynamics.
Therefore, the results suggest that the combined study of geophysical
data and informations from numerical simulations can allow in a near future
a more ecient evaluation of the short term volcanic hazard.
10
Vassalli, Melissa <1977>. "Numerical simulations of magma chamber dynamics at Campi Flegrei, and associated seismicity, deformation and gravity changes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/986/.
Full textAbstract:
Understanding the complex relationships between quantities measured
by volcanic monitoring network and shallow magma processes is a crucial
headway for the comprehension of volcanic processes and a more realistic
evaluation of the associated hazard. This question is very relevant at Campi
Flegrei, a volcanic quiescent caldera immediately north-west of Napoli (Italy).
The system activity shows a high fumarole release and periodic ground slow
movement (bradyseism) with high seismicity. This activity, with the high
people density and the presence of military and industrial buildings, makes
Campi Flegrei one of the areas with higher volcanic hazard in the world.
In such a context my thesis has been focused on magma dynamics due
to the refilling of shallow magma chambers, and on the geophysical signals
detectable by seismic, deformative and gravimetric monitoring networks that
are associated with this phenomenologies. Indeed, the refilling of magma
chambers is a process frequently occurring just before a volcanic eruption;
therefore, the faculty of identifying this dynamics by means of recorded signal
analysis is important to evaluate the short term volcanic hazard.
The space-time evolution of dynamics due to injection of new magma
in the magma chamber has been studied performing numerical simulations
with, and implementing additional features in, the code GALES (Longo et al.,
2006), recently developed and still on the upgrade at the Istituto Nazionale di
Geofisica e Vulcanologia in Pisa (Italy). GALES is a finite element code based
on a physico-mathematical two dimensional, transient model able to treat
fluids as multiphase homogeneous mixtures, compressible to incompressible.
The fundamental equations of mass, momentum and energy balance
are discretised both in time and space using the Galerkin Least-Squares and
discontinuity-capturing stabilisation technique. The physical properties of
the mixture are computed as a function of local conditions of magma composition,
pressure and temperature.The model features enable to study a broad
range of phenomenologies characterizing pre and sin-eruptive magma dynamics
in a wide domain from the volcanic crater to deep magma feeding
zones.
The study of displacement field associated with the simulated fluid dynamics
has been carried out with a numerical code developed by the Geophysical
group at the University College Dublin (O’Brien and Bean, 2004b),
with whom we started a very profitable collaboration. In this code, the seismic
wave propagation in heterogeneous media with free surface (e.g. the
Earth’s surface) is simulated using a discrete elastic lattice where particle interactions
are controlled by the Hooke’s law. This method allows to consider
medium heterogeneities and complex topography.
The initial and boundary conditions for the simulations have been defined
within a coordinate project (INGV-DPC 2004-06 V3_2 “Research on active
volcanoes, precursors, scenarios, hazard and risk - Campi Flegrei”), to which
this thesis contributes, and many researchers experienced on Campi Flegrei
in volcanological, seismic, petrological, geochemical fields, etc. collaborate.
Numerical simulations of magma and rock dynamis have been coupled as
described in the thesis.
The first part of the thesis consists of a parametric study aimed at understanding
the eect of the presence in magma of carbon dioxide in magma in
the convection dynamics. Indeed, the presence of this volatile was relevant
in many Campi Flegrei eruptions, including some eruptions commonly considered
as reference for a future activity of this volcano. A set of simulations
considering an elliptical magma chamber, compositionally uniform, refilled
from below by a magma with volatile content equal or dierent from that
of the resident magma has been performed. To do this, a multicomponent
non-ideal magma saturation model (Papale et al., 2006) that considers the
simultaneous presence of CO2 and H2O, has been implemented in GALES.
Results show that the presence of CO2 in the incoming magma increases its
buoyancy force promoting convection ad mixing. The simulated dynamics
produce pressure transients with frequency and amplitude in the sensitivity
range of modern geophysical monitoring networks such as the one installed
at Campi Flegrei .
In the second part, simulations more related with the Campi Flegrei volcanic
system have been performed. The simulated system has been defined
on the basis of conditions consistent with the bulk of knowledge of Campi
Flegrei and in particular of the Agnano-Monte Spina eruption (4100 B.P.),
commonly considered as reference for a future high intensity eruption in this
area. The magmatic system has been modelled as a long dyke refilling a small shallow magma chamber; magmas with trachytic and phonolitic composition
and variable volatile content of H2O and CO2 have been considered. The
simulations have been carried out changing the condition of magma injection,
the system configuration (magma chamber geometry, dyke size) and the resident
and refilling magma composition and volatile content, in order to study
the influence of these factors on the simulated dynamics. Simulation results
allow to follow each step of the gas-rich magma ascent in the denser magma,
highlighting the details of magma convection and mixing. In particular, the
presence of more CO2 in the deep magma results in more ecient and faster
dynamics. Through this simulations the variation of the gravimetric field has
been determined.
Afterward, the space-time distribution of stress resulting from numerical
simulations have been used as boundary conditions for the simulations of
the displacement field imposed by the magmatic dynamics on rocks. The
properties of the simulated domain (rock density, P and S wave velocities)
have been based on data from literature on active and passive tomographic
experiments, obtained through a collaboration with A. Zollo at the Dept. of
Physics of the Federici II Univeristy in Napoli. The elasto-dynamics simulations
allow to determine the variations of the space-time distribution of
deformation and the seismic signal associated with the studied magmatic dynamics.
In particular, results show that these dynamics induce deformations
similar to those measured at Campi Flegrei and seismic signals with energies
concentrated on the typical frequency bands observed in volcanic areas.
The present work shows that an approach based on the solution of equations
describing the physics of processes within a magmatic fluid and the
surrounding rock system is able to recognise and describe the relationships
between geophysical signals detectable on the surface and deep magma dynamics.
Therefore, the results suggest that the combined study of geophysical
data and informations from numerical simulations can allow in a near future
a more ecient evaluation of the short term volcanic hazard.
11
Schultz, Karl Ulrich. "Etiology of perceived strength changes in the muscles of the legs following locomotion under simulated low gravity." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/49946.
Full text
12
Mahmoud, Ahmad. "Syria-EU Bilateral Trade Relation : An empirical analysis of the changes in export demand between 2006 and 2009." Thesis, Internationella Handelshögskolan, Högskolan i Jönköping, IHH, Nationalekonomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-19092.
Full textAbstract:
This study explores the impact of economic downturn in the EU-27 on Syrian trade and the sensitivity of oil and petroleum products to this downturn. This is carried out using a derivation of the gravity model to determine the export demand. Syrian export with its top 30 trading partners as well as the EU-27 are taken into consideration along with various other trade determinants when measuring the changes in total export volume. The study finds that EU-27 is an important source of demand for Syria, but a downturn in the EU economy will not necessarily have a detrimental effect on Syrian economy. On the other hand, oil plays a far more important role on the country’s exports and its demand is less sensitive to economic fluctuations.
13
Chatterjee, Ani. "Cellular, molecular, and electrophysiological changes in single cells of Ceratopteris during the period of polarity fixation by gravity /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
14
Agus, Nugroho. "ECONOMIC ANALYSIS ON PRODUCTION CHANGES, MARKET INTEGRATION AND EXPORT CHALLENGES OF COFFEE SECTOR IN INDONESIA." Kyoto University, 2016. http://hdl.handle.net/2433/215968.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第19902号
農博第2185号
新制||農||1044(附属図書館)
学位論文||H28||N5006(農学部図書室)
32979
京都大学大学院農学研究科生物資源経済学専攻
(主査)教授 福井 清一, 教授 伊藤 順一, 准教授 沈 金虎
学位規則第4条第1項該当
15
Creutzfeldt, Noah Angelo Benjamin. "The effect of water storages on temporal gravity measurements and the benefits for hydrology." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4857/.
Full textAbstract:
Temporal gravimeter observations, used in geodesy and geophysics to study variation of the Earth’s gravity field, are influenced by local water storage changes (WSC) and – from this perspective – add noise to the gravimeter signal records. At the same time, the part of the gravity signal caused by WSC may provide substantial information for hydrologists. Water storages are the fundamental state variable of hydrological systems, but comprehensive data on total WSC are practically inaccessible and their quantification is associated with a high level of uncertainty at the field scale.
This study investigates the relationship between temporal gravity measurements and WSC in order to reduce the hydrological interfering signal from temporal gravity measurements and to explore the value of temporal gravity measurements for hydrology for the superconducting gravimeter (SG) of the Geodetic Observatory Wettzell, Germany.
A 4D forward model with a spatially nested discretization domain was developed to simulate and calculate the local hydrological effect on the temporal gravity observations. An intensive measurement system was installed at the Geodetic Observatory Wettzell and WSC were measured in all relevant storage components, namely groundwater, saprolite, soil, top soil and snow storage. The monitoring system comprised also a suction-controlled, weighable, monolith-filled lysimeter, allowing an all time first comparison of a lysimeter and a gravimeter. Lysimeter data were used to estimate WSC at the field scale in combination with complementary observations and a hydrological 1D model. Total local WSC were derived, uncertainties were assessed and the hydrological gravity response was calculated from the WSC. A simple conceptual hydrological model was calibrated and evaluated against records of a superconducting gravimeter, soil moisture and groundwater time series. The model was evaluated by a split sample test and validated against independently estimated WSC from the lysimeter-based approach.
A simulation of the hydrological gravity effect showed that WSC of one meter height along the topography caused a gravity response of 52 µGal, whereas, generally in geodesy, on flat terrain, the same water mass variation causes a gravity change of only 42 µGal (Bouguer approximation). The radius of influence of local water storage variations can be limited to 1000 m and 50 % to 80 % of the local hydro¬logical gravity signal is generated within a radius of 50 m around the gravimeter.
At the Geodetic Observatory Wettzell, WSC in the snow pack, top soil, unsaturated saprolite and fractured aquifer are all important terms of the local water budget. With the exception of snow, all storage components have gravity responses of the same order of magnitude and are therefore relevant for gravity observations. The comparison of the total hydrological gravity response to the gravity residuals obtained from the SG, showed similarities in both short-term and seasonal dynamics. However, the results demonstrated the limitations of estimating total local WSC using hydrological point measurements.
The results of the lysimeter-based approach showed that gravity residuals are caused to a larger extent by local WSC than previously estimated. A comparison of the results with other methods used in the past to correct temporal gravity observations for the local hydrological influence showed that the lysimeter measurements improved the independent estimation of WSC significantly and thus provided a better way of estimating the local hydrological gravity effect. In the context of hydrological noise reduction, at sites where temporal gravity observations are used for geophysical studies beyond local hydrology, the installation of a lysimeter in combination with complementary hydrological measurements is recommended.
From the hydrological view point, using gravimeter data as a calibration constraint improved the model results in comparison to hydrological point measurements. Thanks to their capacity to integrate over different storage components and a larger area, gravimeters provide generalized information on total WSC at the field scale. Due to their integrative nature, gravity data must be interpreted with great care in hydrological studies. However, gravimeters can serve as a novel measurement instrument for hydrology and the application of gravimeters especially designed to study open research questions in hydrology is recommended.Zeitabhängigen Gravimetermessungen, die in der Geodäsie und der Geophysik eingesetzt werden, um Variationen des Erdschwerefelds zu messen, werden durch lokale Wasserspeicheränderungen beeinflusst und verursachen – aus dieser Perspektive – ein hydrologisches Störsignal in den Gravimetermessungen. Gleichzeitig bietet der Teil des Gravimetersignals, der durch Wasserspeicheränderungen hervorgerufen wird, das Potential wichtige Informationen über hydrologische Speicher zu gewinnen, da zwar Wasserspeicher eine grundlegende Zustandsgröße hydrologischer Systeme darstellt, jedoch ihre Quantifizierung mit einem hohen Maß an Unsicherheiten auf der Feldskala behaftet ist. Diese Studie untersucht die Beziehung zwischen zeitabhängigen Gravimetermessungen und Wasserspeicheränderungen, um die Gravimetermessungen von dem hydrologischen Störsignal zu bereinigen und um den Nutzen der Gravimetermessungen für die Hydrologie zu erkunden. Dies geschieht am Beispiel des Supraleitgravimeters (SG) des Geodätischen Observatoriums Wettzell in Deutschland. Ein 4D Vorwärtsmodel mit einer räumlich genesteten Diskretisierungsdomäne wurde entwickelt, um die lokalen hydrologischen Masseneffekte auf Gravimetermessungen zu simulieren. Des Weiteren wurde ein intensives Messsystem am Geodätischen Observatorium Wettzell installiert, um die Wasserspeicheränderungen in allen relevanten Speicherkomponenten, also im dem Grundwasser, in der ungesättigten Zone und im Schneespeicher zu messen. Das Monitoringsystem beinhaltete auch einen wägbaren, monolithischen Lysimeter mit Matrixpotentialübertragung, der es uns ermöglichte, zum ersten Mal einen Lysimeter direkt mit einem Gravimeter zu vergleichen. Die Lysimetermessungen wurden in Kombination mit komplementären hydrologischen Beobachtungen und einem 1D-Modell verwendet, um die Wasserspeicheränderungen auf der Feldskala zu bestimmen. Die Gesamtwasserspeicheränderungen wurden bestimmt, Unsicherheiten abgeschätzt und der hydrologische Masseneffekt auf Gravimetermessungen berechnet. Schlussendlich wurde ein einfaches, konzeptionelles, hydrologisches Modell mittels der Zeitreihen von dem SG, Bodenfeuchte- und Grundwassermessungen kalibriert und evaluiert. Das Modell wurde durch einen “Split-Sample-Test” evaluiert und basierend auf unabhängig bestimmten Wasserspeicheränderungen bestimmt auf Grundlage der Lysimetermessungen validiert. Die Simulation des hydrologischen Masseneffektes auf Gravimetermessungen zeigte, dass Wasserspeicheränderungen von einem Meter Höhe entlang der Topographie, einen Erdschwereeffekt von 52 µGal hervorriefen, während in der Geodäsie im Allgemeinen die gleiche Wassermassenvariation in flachem Terrain eine Erdschwereeffekt von nur 42 µGal (Bouguer-Platte) hervorruft. Der Einflussradius der lokalen Wasserspeicheränderungen kann auf 1000 m begrenzt werden, und 50 % bis 80 % des lokalen hydrologischen Erdschweresignals wird in einem Radius von 50 m um den Gravimeter generiert. Wasserspeichervariationen in der Schneedecke, im Oberboden, dem ungesättigten Saprolith und im gelüfteten Aquifer, sind allesamt wichtige Größen der lokalen Wasserbilanz. Mit der Ausnahme von Schnee beeinflussen alle Speicheränderungen die Gravimetermessungen in derselben Größenordnung und sind daher für die Gravimetermessungen von Bedeutung. Ein Vergleich des lokalen hydrologischen Gravitationseffektes mit den SG Residuen zeigte sowohl ereignisbezogene als auch saisonalen Übereinstimmungen. Weiterhin zeigten die Ergebnisse jedoch auch die Grenzen bei der Bestimmung der gesamten lokalen Wasserspeichervariationen mithilfe hydrologischer Punktmessungen auf. Die Ergebnisse des Lysimeter-basierten Ansatzes zeigten, dass SG Residuen mehr noch, als bisher aufgezeigt, durch lokale Wasserspeicheränderungen hervorgerufen werden. Ein Vergleich der Resultate mit anderen Methoden, die in der Vergangenheit zur Korrektur zeitabhängiger Erdschwerebeobachtungen durch Bestimmung des lokalen hydrologischen Masseneffekte verwendet wurden, zeigte, dass die unabhängige Berechnung von Wasserspeicheränderungen durch Lysimetermessungen erheblich verbessert werden kann und dass diese somit eine verbesserte Methode zur Bestimmung des lokalen hydrologischen Erdschwereeffekts darstellt. Die Installation eines Lysimeters ist somit im Zusammenhang mit einer Reduzierung des hydrologischen Störsignals und an Standorten, wo zeitabhängige Erdschwerebeobachtungen für geophysikalische Studien, die über die lokale Hydrologie hinausgehen verwendet werden, zu empfehlen. Aus hydrologischer Sicht zeigte diese Studie, dass die Verwendung von zeitabhängigen Gravimetermessungen als Kalibrierungsdaten die Modellergebnisse im Vergleich zu hydrologischen Punktmessungen verbesserten. Auf Grund ihrer Fähigkeit, über verschiedene Speicherkomponenten und ein größeres Gebiet zu integrieren, bieten Gravimeter verallgemeinerte Informationen über die Gesamtwasserspeicherveränderungen auf der Feldskala. Diese integrative Eigenschaft macht es notwendig, Erdschweredaten in hydrologischen Studien mit großer Vorsicht zu interpretieren. Dennoch können Gravimeter der Hydrologie als neuartiges Messinstrument dienen und die Nutzung von Gravimetern, die speziell für die Beantwortung noch offener Forschungsfragen der Hydrologie entwickelt wurden wird hier empfohlen.
16
Nooner, Scott L. "Gravity changes associated with underground injections of CO₂ at the Sleipner storage reservoir in the North Sea, and other marine geodetic studies /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3171110.
Full text
17
Garcia, Raquel Soledad. "Topology change in quantum gravity." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322405.
Full text
18
Joodaki, Gholamreza. "Earth Mass Change Tracking Using GRACE Satellite Gravity Data." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23969.
Full textAbstract:
This project is dealing with the estimation of present-day Earth’s mass transport and its redistribution by using observations from Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE measures the gravity fluctuations which are primarily related to redistribution of water around the globe. GRACE data has yield profound new insights into melting rates of ice sheets and mountain glaciers, land hydrology, ocean circulation, and sea level rise. In this project, first, the ice melting rate in the Greenlandic ice sheet is studied. This is done by analyzing the time series of monthly GRACE release 04 gravity field solutions from three different data sets, CSR (Center for Space Research), GFZ (Geoforschungszentrum), and JPL (Jet Propulsion Laboratory) with respect to their long-term temporal changes. The data are de-striped by applying a non-isotropic filter. Also, a method for reducing the leakage effects is developed. As an example, the ice mass balance is estimated of -163 ± 20 Gt/yr based on the CSR release 04 and smoothing by a parameter of a =1013 during April 2002 to February 2010. The results also show that the spatial distribution of the ice mass loss is changing with time and the ice mass loss is accelerating. For example, its acceleration is a rate of -32±6 Gt/yr2 during 2002 to 2011. The second part of this project is concern with the determination of water mass changes in the Nordic Seas. It is determined by analyzing the time series of monthly GRACE level 2 release 04 data from GFZ during October 2002 to October 2010. The striping errors are reduced by using a non-isotropic filter and the data are smoothed by a parameter of a =1014 according to Gaussian smoothing radius of 530 km. The time series of water mass changes are used to study the steric sea height variations over the Nordic Seas during the same period of study. This is done by analyzing the time series of monthly sea level anomaly from ENVISAT (Environmental Satellite) altimetry data, cycles 10 to 93, among the time series of water mass changes. The results show that the interdisciplinary nature of the GRACE measurements have opened up the unique opportunity to enhance our knowledge on the interaction between Earth system components and their response to climate variability. In the last part of this project, variations of the continental total water storage, total groundwater storage, and anthropogenic contributions across the Middle East are studied. By using a mascon analysis method and GRACE level 2 release 05 data from CSR during February 2003 to December 2012, the time series of total water storage, total ground water storage and anthropogenic contributions are estimated over this region. The region is subdivided to seven mascons including Iran, Iraq, Syria, eastern Turkey (east of 35º longitude), northern and southern Saudi Arabia (north and south of 25º latitude), and the region immediately west of Caspian Sea. The total groundwater storage, and anthropogenic contributions are separated from the total water storage by using the CLM4.5 (version 4.5 of the Community Land Model) hydrological model. The results show that Iran with a rate of 25±6 Gt/yr has the most groundwater loss rate during February 2003 to December 2012 in this region. The Iran’s rate of groundwater loss from the GRACE data is supported by an analysis of in situ well data from across Iran. The results also show that the GRACE mission is able to monitor monthly water storage changes within river basins and aquifers that are 200,000 km2 or larger in area, and, can contribute to water management at regional and national scales, and to international policy discussions as well.
19
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.
Full textAbstract:
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.
20
Rickles, Dean Peter. "Spacetime, change and identity : classical and quantum gravity in philosophical focus." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414877.
Full text
21
Diana, Antoine. "Liquid-vapour phase change : nucleate boiling of pure fluid and nanofluid under different gravity levels." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/65842/1/Antoine_Diana_Thesis.pdf.
Full textAbstract:
This research was a step towards the comprehension of the nano-particles interaction with bubbles created during boiling. It was aimed at solving the controversies of whether the heat transfer is enhanced or deteriorated during the boiling of the nanofluid. Experiments were conducted in normal gravity and reduced gravity environments on-board the European Space Agency Parabolic Flight Program. The local modification of the thermo-physical properties of the fluid and moreover the modification experienced in the liquid microlayer under the growing vapour bubble were the dominant factors in explaining the mechanisms of the boiling behaviour of the nanofluid.
22
Wang, Lei. "Coseismic Deformation Detection and Quantification for Great Earthquakes Using Spaceborne Gravimetry." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331098701.
Full text
23
Ohata, Koji. "Formation conditions of bedforms under sediment-laden gravity currents." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263478.
Full text
24
Chen, Yiqun. "Recovery of terrestrial water storage change from low-low satellite-to-satellite tracking." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196098152.
Full text
25
Wilkman, Mats. "Determinants of Swedish Pharmaceutical Exports." Thesis, Internationella Handelshögskolan, Högskolan i Jönköping, IHH, Nationalekonomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-19325.
Full textAbstract:
In this thesis factors that explain Swedish pharmaceutical export as been analyzed. The period investigated is from 1995 to 2010. The investigation is concluded through the use of a gravity model. It investigates not only the GDP and distance variable but also the effects of GDP/capita, exchange rates and the effect of being a part of the internal market of EU. The effects of having access to the ocean and if the country has English as its official language is investigated as well as the effect of sharing the same religion. The results show that only a smaller subset of countries make up for most of the pharmaceutical export. The results also shows that the pharmaceutical export can be explained by the same variables as most other goods.
26
Chima, Kelvin Ikenna. "Tectonostratigraphic evolution of the Western Niger Delta from the Cretaceous to Present." Electronic Thesis or Diss., Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2020SORUS053.pdf.
Full textAbstract:
Le basculement du delta du Niger occidental au début de son évolution au Crétacé a entraîné le développement d'une surface sismique régionale à centre de bassin, ce qui a facilité le glissement de la gravité du Crétacé au Serravallien. Une augmentation globale des taux de sédimentation s'est produite dans l'ouest du delta du Niger, du Serravallien au Pliocène et pendant la plus grande partie du Pléistocène, ce qui a favorisé la propagation de la gravité. Des schistes mobiles ont été actifs dans l'ouest du delta du Niger, au moins pour le Burdigalien, et ont contrôlé la morphologie, la distribution et les schémas de dépôt des canaux sous-marins jusqu'au Pliocène et au Pléistocène. La stratigraphie du Pliocène et du Pléistocène des bassins intra-pente du Delta du Niger occidental a été contrôlée par des forçages allocycliques de 400 ka et 100 ka d'excentricité, liés aux changements glacio-eustatiques du niveau de la mer au cours du Pléistocène moyen-messinien et du Pléistocène moyen-présent respectivement, et par des forçages tectoniques des bassins liés à la tectonique des schistes. Malgré les taux de sédimentation relativement plus faibles estimés sur le plateau continental et le talus du delta du Niger occidental depuis le début du Pliocène, l'augmentation globale de l'effondrement par gravité, de l'épaisseur des sédiments et de leur distribution du plateau au bassin profond, suggère une augmentation globale de la sédimentation dans cette région. Toutefois, dans l'est du delta du Niger, l'affaissement actif des failles normales régionales et la migration déduite des lobes du delta auraient contribué à la réduction continue de la sédimentation depuis le Pléistocène. Cette thèse améliore non seulement notre compréhension de l'évolution tectono-stratigraphique du delta occidental du Niger, mettant en évidence les styles complexes de piégeage structurel et stratigraphique notamment dans les systèmes en eau profonde sous-explorés, mais montre également la présence de dépôts syn-rift pouvant héberger un prospect Crétacé-Paléogène dans le delta occidental du NigerThe tilting of the western Niger Delta early during its evolution in the Cretaceous, resulted in the development of basin centre-dipping regional seismic surface, which facilitated gravity gliding from the Cretaceous to the Serravallian. An overall increase in sedimentation rates occurred in the western Niger Delta onwards from the Serravallian to the Pliocene and most of the Pleistocene, favouring gravity spreading. Mobile shales have been active in the western Niger Delta for at least the Burdigalian, and controlled submarine channels morphology, distribution and depositional patterns up to the Pliocene and the Pleistocene. The Pliocene and Pleistocene stratigraphy of the western Niger Delta intraslope basins were controlled by allocyclic forcings of 400 ka and 100 ka eccentricity, linked to glacio-eustatic sea-level changes over the Messinian-middle Pleistocene and the middle Pleistocene-present respectively, and basin tectonics forcing linked to shale tectonics. Despite the relatively lower sedimentation rates estimated on the western Niger Delta continental shelf and slope since the early Pliocene, the overall increase in gravity collapse, sediment thickness and distribution from the shelf to the deep basin, suggest an overall increase in sedimentation in this region. However, in the eastern Niger Delta, the actively subsiding counter regional normal faults and inferred delta lobe migration are thought to have contributed to the ongoing reduction in sedimentation since the Pleistocene. This PhD research not only improves our understanding of the tectonostratigraphic evolution of the western Niger Delta, highlighting the complex structural and stratigraphic trapping styles notably in the underexplored deepwater systems, but also shows the presence of syn-rift deposits that may host the Cretaceous-Paleogene petroleum play in the offshore western Niger Delta
27
Al, Habbaki Patricia. "Les incidences des politiques de commerce extérieur et de change sur les échanges commerciaux des pays du Mashrek (Liban, Syrie Jordanie et Egypte)." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR1007/document.
Full textAbstract:
En dépit du renforcement de leur ouverture commerciale, le commerce extérieur des pays du Mashrek a presque toujours affiché des chiffres plutôt négatifs. Selon la littérature, l'ouverture commerciale est une des conditions permettant une croissance vigoureuse d'un pays. Néanmoins, la tendance constatée à la lumière des données du commerce de ces pays, traduirait une réalité alarmante. L'ouverture ne s'est pas traduite par une accélération des niveaux des investissements, ni par une création d'emplois. Est-ce que les politiques commerciales et de change menées par les pays du Mashrek sont responsables de cette persistance des déficits commerciaux ? Motivée par l’aggravation remarquable du solde de la balance commerciale libanaise survenue dans le profil global des échanges extérieurs du Liban, la présente recherche examine le comportement dynamique des exportations et importations libanaises en comparaison avec ses pays voisins (la Syrie, l’Egypte et la Jordanie) dans un contexte économique régional et international en mutation, en proposant une analyse empirique des déterminants des flux commerciaux ayant pour objet d’établir dans quelle mesure la politique commerciale et de change seraient responsables des faits stylisés observésDespite the strengthening of their commercial openness, the Mashreq countries trade has rather always displayed negative results. According to the literature, opening up trade is one of the conditions leading to any country’s vigorous growth. Nevertheless, the trend found in the light of these countries’ trade data, indicates an alarming reality. The openness was neither translated into accelerated levels of investments nor created new job opportunities. Are the trade and exchange rate policies pursued by the Mashreq countries responsible for this persistence in trade deficits ? Motivated by outstanding worsening deflection of the trade balance in the overall Lebanese external trade profile, the current research examines the dynamic behavior of the Lebanese exports and imports compared to its neighboring countries (Syria, Egypt, and Jordan) in a regional and international changing economic context. An empirical analysis of the trade flows determinants was adopted in order to establish to what extent the trade and Exchange policies would be responsible for the observed stylized facts
28
Patel, Shagufta Usman. "Improving Performance and Drainage of Coalescing Filters." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1279317322.
Full text
29
Yang, Qian. "Applications of Satellite Geodesy in Environmental and Climate Change." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6440.
Full textAbstract:
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.
30
Azzolin, Marco. "Experimental study of phase change heat transfer in minichannels for ground and space applications." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424393.
Full textAbstract:
Two-phase heat transfer is widely encountered in minichannels heat exchangers such as air-cooled condensers and evaporators for automotive, compact devices for electronic cooling, aluminum condenser for air-conditioning applications, loop heat pipes and capillary pumped loops for space applications. Nowadays there is also an increasing interest on new refrigerants, pure and blended, with a low-GWP.
This thesis aims at studying the physical phenomena of condensation by investigating the effect of gravity inside small channels, presenting an experimental analysis during normal gravity and microgravity conditions. Another objective of this thesis is to analyze the two-phase heat transfer performance of non-azeotropic mixtures, with low-GWP, in minichannels. Regarding mixtures the work focused not only on condensation heat transfer but also on flow boiling and two phase pressure drop.
In the first part of this thesis the design and the realization of a new test section to study the effect of gravity during convective condensation is presented. The new test section has an internal diameter of 3.38 mm and it allows to measure quasi-local heat transfer coefficients and to visualize the flow pattern. Quasi-local heat transfer coefficients measured on ground during condensation of R134a at 40°C and mass velocities between 50 and 200 kg m-2 s-1 are presented. The flow patterns visualized are compared with flow pattern maps available in the literature and the experimental heat transfer coefficients with different models for condensation. The new test section has been also used to study convective condensation in microgravity conditions during the 62nd ESA Parabolic Flight Campaign. This has been one of the first attempts to perform heat transfer coefficients measurements and flow pattern visualizations on normal gravity and microgravity conditions during convective condensation inside tubes. The deep connection between gravity effect and flow pattern are shown in the images.
Regarding on-ground applications, in the recent years much attention has been paid to the possible use of fluorinated propene isomers for the substitution of HFC fluids being in most cases high-GWP refrigerants. However, the available HFOs (hydrofluoroolefins) cannot cover all the air-conditioning, heat pump, and refrigeration systems when used as pure fluids because their thermodynamic properties are not suitable for all operating conditions; therefore some solutions may be found using blends of refrigerants, to satisfy the demand for a wide range of working conditions.
The second part of this thesis presents an experimental study of the two-phase heat transfer for a R32/R1234ze(E) non-azeotropic mixture, at different mass compositions, inside a 0.96 mm inner diameter minichannel. As first step, frictional pressure gradient during adiabatic two-phase flow has been investigated. The experimental data are also compared with several models available in the literature. Local heat transfer coefficients have been then measured during condensation of the R32/R1234ze(E) mixture at three different mass compositions (23/77%, 46/54 and 75/25% by mass). The new experimental data are compared to those of pure R1234ze(E) and R32. This allows to analyze the heat transfer penalization due to the mass transfer resistance occurring during condensation of this zeotropic mixture and to assess about suitable predicting models. The present work reports also the local heat transfer coefficient measured during flow boiling of the R32/R1234ze(E) mixture (50/50% by mass) at a pressure of 14 bar, which corresponds to a bubble temperature of 26.2 °C. The flow boiling data, taken in the 0.96 mm minichannel, are discussed with particular regard to the mass transfer mechanism. The new experimental data are also compared to flow boiling data of pure R1234ze(E) and pure R32. This flow boiling database, encompassing more than 300 experimental points at different values of mass velocity, heat flux and vapor quality, is compared with available correlations in the literature. The introduction of a correction to account for the additional mass transfer resistance is discussed and such correction is found to be necessary and proper to provide a correct sizing of the evaporator.Lo scambio termico bifase in minicanali è utilizzato in diverse applicazioni come ad esempio, condensatori ed evaporatori ad aria nel settore automobilistico, sistemi compatti per il raffreddamento di elettronica, condensatori in alluminio per applicazioni di climatizzazione, tubi di calore per applicazioni spaziali. In più oggi c'è un crescente interesse verso i nuovi fluidi, puri e in miscela, con basso GWP. Questo lavoro di tesi si propone di studiare i fenomeni fisici dello scambio termico in condensazione indagando l'effetto della gravità all'interno di canali con piccolo diametro, presentando un'analisi sperimentale in condizioni di gravità normale e di microgravità. Un altro obiettivo di questa tesi è quello di analizzare le prestazioni di miscele non azeotropiche, a basso GWP, durante lo scambio termico bifase in minicanali. Per quanto riguarda le miscele si analizzerà sperimentalmente non solo lo scambio termico durante la condensazione ma anche la vaporizzazione e le cadute di pressione bifase. Nella prima parte di questa tesi viene presentata la progettazione e la realizzazione di una nuova sezione sperimentale per studiare l'effetto della gravità durante lo scambio termico in condensazione. La nuova sezione di prova ha un diametro interno di 3.38 mm e permette di misurare i coefficienti di scambio termico quasi-locali e di visualizzare il regime di deflusso. I coefficienti di scambio termico in condensazione sono stati misurati con R134a alla temperatura di saturazione di 40 °C e per portate specifiche tra 50 e 200 kg m-2 s-1. I regimi di deflusso visualizzati sono stati confrontati con quelli predetti dalle mappe di deflusso disponibili in letteratura e i coefficienti di scambio termico sperimentali con modelli sviluppati per la condensazione. La nuova sezione sperimentale è stata utilizzata anche durante la 62° Campagna di Volo Parabolico di ESA per studiare lo scambio termico in condensazione in condizioni di microgravità. Questo studio è uno dei primi tentativi di effettuare misure dei coefficienti di scambio termico e visualizzazioni dei regimi di flusso in condizioni di gravità normale e di microgravità durante la condensazione all'interno di tubi. Il legame profondo tra effetto della gravità e regime di flusso è analizzato servendosi delle immagini acquisite. Per quanto riguarda le applicazioni terrestri, negli ultimi anni molto interesse si è sviluppato intorno al possibile utilizzo di isomeri fluorurati del propene per la sostituzione di fluidi HFC (idrofluorocarburi) che nella maggior parte dei casi sono ad alto GWP. Tuttavia gli HFO (idrofluoroolefine) disponibili non possono coprire tutte le applicazioni di climatizzazione, pompe di calore e sistemi di refrigerazione quando vengono utilizzati come fluidi puri perché le loro proprietà termodinamiche non sono adatte a tutte le condizioni operative; quindi una soluzione è quella di utilizzarli in miscela con altri refrigeranti. La seconda parte di questa tesi presenta uno studio sperimentale dello scambio termico bifase per una miscela non azeotropica di R32/R1234ze(E), a diverse composizioni di massa, all'interno di un minicanale con diametro interno di 0.96 mm. Come primo passo si sono studiate le cadute di pressione durante il deflusso adiabatico bifase. I dati sperimentali sono stati confrontati con diversi modelli disponibili in letteratura. Successivamente i coefficienti locali di scambio termico in condensazione sono stati misurati per la miscela R32/R1234ze(E) a tre diverse composizioni di massa (23/77%, 46/54 e 75/25%). I nuovi dati sperimentali sono confrontati con quelli dei componenti puri R1234ze(E) e R32. Questo ha permesso di analizzare la penalizzazione introdotta dalla resistenza al trasporto di massa e di valutare i modelli teorici in grado di predirla. In seguito vengono anche presentati i coefficienti di scambio termico misurati durante la vaporizzazione convettiva della miscela R32/R1234ze(E) (composizione 50/50%) ad una pressione di 14 bar, corrispondente ad una temperatura di bolla di 26.2 °C. I risultati sperimentali, ricavati nel minicanale di diametro 0.96 mm, sono stati discussi con particolare riguardo al meccanismo di trasporto di massa e successivamente confrontati con quelli dei fluidi puri R1234ze(E) e R32. I nuovi dati, più di 300 punti sperimentali a differenti valori di portata specifica, flusso termico e titolo di vapore, sono stati confrontati con le correlazioni disponibili in letteratura. L'introduzione di una correzione per tenere conto dell'ulteriore resistenza al trasporto di massa è stata discussa e risulta essere necessaria per un corretto dimensionamento degli evaporatori.
31
Abel, Guy, Michael Brottrager, Cuaresma Jesus Crespo, and Raya Muttarak. "Climate, Conflict and Forced Migration." Elsevier, 2019. http://dx.doi.org/10.1016/j.gloenvcha.2018.12.003.
Full textAbstract:
Despite the lack of robust empirical evidence, a growing number of media reports attempt to link climate change
to the ongoing violent conflicts in Syria and other parts of the world, as well as to the migration crisis in Europe.
Exploiting bilateral data on asylum seeking applications for 157 countries over the period 2006-2015, we assess
the determinants of refugee flows using a gravity model which accounts for endogenous selection in order to
examine the causal link between climate, conflict and forced migration. Our results indicate that climatic
conditions, by affecting drought severity and the likelihood of armed conflict, played a significant role as an
explanatory factor for asylum seeking in the period 2011-2015. The effect of climate on conflict occurrence is
particularly relevant for countries in Western Asia in the period 2010-2012 during when many countries were
undergoing political transformation. This finding suggests that the impact of climate on conflict and asylum
seeking flows is limited to specific time period and contexts.
32
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.
Full textAbstract:
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.
33
Trejo, Peimbert Esli. "Dynamics and Transfers in two phase flows with phase change in normal and microgravity conditions." Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/23986/1/Trejo_Esli.pdf.
Full textAbstract:
Two-phase flows with or without phase change are present in terrestrial and space applications like thermal control of satellites, propellant supply for launchers, and waste water treatment for space exploration missions. Flow boiling experiment with HFE7000 were conducted in a heated tube in vertical upward flow on ground and in microgravity conditions to collect data on flow patterns, pressure drops, heat transfers, void fraction. Void fraction measurements allowed to measure mean gas velocity and the liquid film thickness in annular flow. In microgravity condition, the liquid film thickness and the interfacial shear stress are significantly lower than in normal gravity. A detail analysis of the film structure was performed by image processing. The impact of gravity and liquid and vapour superficial velocities on the disturbance waves velocities and frequencies was investigated. Two different measurement techniques were used and compared to determine the heat transfer coefficient. For quality values greater than 0.2, HTC is not sensitive to gravity and is in good agreement with classical correlations of the literature. For qualities smaller than 0.1, in the subcooled nucleate boiling regime HTC is significantly smaller in microgravityconditions.
34
Sanders, Jessica R. "Actions/Objects: A Knotting." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276036952.
Full text
35
Bele, Daniel. "Warden i Israel : En studie av Wardens tillämpning i Israels luftkrig 2006-2009." Thesis, Försvarshögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-4053.
Full textAbstract:
Den amerikanske luftmaktsteoretikern John A Warden III har skrivit ett flertal artiklar och böcker om vad han anser är det bästa sättet att använda luftmakt. Warden förordar luftmaktens offensiva natur och eftersträvar ett snabbt, för egen del, fördelaktigt slut på en konflikt. Warden har bl.a. liknat fienden vid ett system, där han menar att strävan skall ligga i att slå ut fiendens ledarskikt vilket får tillföljd att dess vilja till strid upphör. I detta arbete ges en sammanfattning av, enligt författaren, centrala delar av Wardens teorier. Sammanfattningen mynnar ut i tre stycken parametrar som kommer att utgöra Wardens teorier i detta arbete. De tre parametrarna är "enemy as a system", "center of gravity" samt "parallell attack". Dessa parametrar ligger sedan till grund för en analys av Israels luftkampanjer i dess krig mot Hizbollah 2006, Operation Change of Direction samt dess krig mot Hamas 2008-09, Operation Cast Lead. Syftet med detta är att ta reda på om Israel använde sig av Wardens teorier under dessa båda operationer. Anledningen till valet av dessa två konflikter är att Israel bl.a. sin doktrin slagit fast att de aldrig har råd att förlora ett krig. Detta tvingar Israel att optimera sin taktisering. Slutsatsen blev att det tydligt går att se att Wardens teorier genomsyrade Operation Change of Direction. Det var enbart "parallell attack" som inte tydligt efterföljdes genom hela operationen. Under Operation Cast Lead däremot så följde Israel Wardens teorier i mycket mindre utsträckning. Det var enbart "center of gravity" som följdes genom hela den operationen.
36
Wimberly, Brent. "Identification of spatiotemporal nutrient patterns and associated ecohydrological trends in the tampa bay coastal region." Honors in the Major Thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/642.
Full textAbstract:
Improvements for environmental monitoring and assessment were achieved to advance our understanding of sea-land interactions and nutrient cycling in a coastal bay.; The comprehensive assessment techniques for monitoring of water quality of a coastal bay can be diversified via an extensive investigation of the spatiotemporal nutrient patterns and the associated eco-hydrological trends in a coastal urban region. With this work, it is intended to thoroughly investigate the spatiotemporal nutrient patterns and associated eco-hydrological trends via a two part inquiry of the watershed and its adjacent coastal bay. The findings show that the onset of drought lags the crest of the evapotranspiration and precipitation curve during each year of drought. During the transition year, ET and precipitation appears to start to shift back into the analogous temporal pattern as the 2005 wet year. NDVI shows a flat receding tail for the September crest in 2005 due to the hurricane impact signifying that the hurricane event in October dampening the severity of the winter dry season in which alludes to relative system memory. The k-means model with 8 clusters is the optimal choice, in which cluster 2 at Lower Tampa Bay had the minimum values of total nitrogen (TN) concentrations, chlorophyll a (Chl-a) concentrations, and ocean color values in every season as well as the minimum concentration of total phosphorus (TP) in three consecutive seasons in 2008. Cluster 5, located in Middle Tampa Bay, displayed elevated TN concentrations, ocean color values, and Chl-a concentrations, suggesting that high colored dissolved organic matter values are linked with some nutrient sources. The data presented by the gravity modeling analysis indicate that the Alafia River Basin is the major contributor of nutrients in terms of both TP and TN values in all seasons. Such ecohydrological evaluation can be applied for supporting the LULC management of climatic vulnerable regions as well as further enrich the comprehensive assessment techniques for estimating and examining the multi-temporal impacts and dynamic influence of urban land use and land cover.B.S.C.E.
Bachelors
Engineering and Computer Science
Civil Engineering
37
Fiorot, Guilherme Henrique. "On unsteady open-channel flows : a contribution to nonstationary sediment transport in runoff flows and to unstable non-Newtonian mudflow studies." Thesis, Rennes, INSA, 2016. http://www.theses.fr/2016ISAR0020/document.
Full textAbstract:
L'objectif général de cette thèse est l'étude de d'écoulement instationnaire du type coulée de boue dans des canaux naturels. La pluie, source du débit liquide, entraine le ruissellement, responsable du mouillage du sol, de la réduction de sa cohésion et de l'érosion des petites particules de sédiments. A partir de là, le transport de sédiments peut augmenter avec le débit et la pente du sol jusqu'à ce que la concentration en particules atteignent des niveau très importants dans la composition du fluide. Dans une première partie, un banc expérimental a été conçu pour simuler des écoulements ruissellants sur un lit mobile. Un système de mesure a été inventé et implémenté pour mesurer le débit solide instantané et le frottement instantané. Ces systèmes sont utilisés pour étudier l'effet des ondes de surface libre sur le transport de sédiments. Ces données sont employées pour corréler les charactéristiques entr l'écoulement et le transport solide. L'analyse des résultats permet d'observer que pour un écoulement moyen donné, la présence des ondes réduit la quantité moyenne des sédiments transportés. Dans une deuxième partie, la dynamique des écoulements très concentrés est étudiée grâce à un modèle de roll waves de première ordre pour les écoulements laminaires des fluides de type Herschel-Bulkley. Les résultats présentés indiquent que des roll wave sont certainement présentes dans un événement naturel publié et pris comme cas d'étude. Les propriétés des ondes prédites sont estimées avec un écart de 8% par rapport à l'amplitude moyenne mesurée. Finalement, la solution théorique pour le profil de vitesse est modifiée pour prendre en considération l'effet de la porosité. La solution mathématique est comparée à des simulations faites avec FLUENT. Une analyse paramétrique est effectuée, et la comparaison avec le cas d'étude déjà publié est améliorée. En conclusion générale, les phénomènes instationnaires qui peuvent apparaitre lors de l'évolution d'une coulée de boue affectent la dynamique générale du système couplé (écoulement-transport sédimentaire) par rapport au cas permanent et uniforme. Vérifier que ce type de phénomènes peut apparaître lors d'un événement naturel comme les coulées de boue doit être un étape importante d'un projet d'ingénierie, afin de limiter les risques de dommagesThis thesis was motivated by the need to better understand time-dependent features related to mudflow evolution on natural sloped channels. Basically, the research is focused on events that are confined in channels formed due to the topography. The rain, source of the liquid discharge, generates the runoff flow which is responsible for wetting the soil surface, promoting reduction of soil cohesiveness and erosion of small particles such as clay and sand. From this point, the sediment transport can increase as small water flows merge and form greater streams. The scenario keeps its evolution until i reaches high concentration of particles in the fluid mixture. In the first part, to study the non-permanent feature of sediment transport, an open-channel experiment was designed for simulating runoff flow over a mobile bed. A measurement system was designed and constructed to instantaneously inspect the solid discharge of particles and the flow friction at the bed. This apparatus is further used to explore the influence of free-surface waves on the sediment transport. Hydraulic properties of flows are qualitatively and quantitatively studied and data are used to correlate characteristics of flow and sediment transport. A set of experimental runs is presented and explored. Analysis of results shows that for fixed flow conditions, waves induce an overall smaller quantity of transported sediment. In a second part, the dynamics of high concentrated flows is addressed and this thesis attempts to appl a first-order roll-wave model for Herschel-Bulkley laminar fluid flow to a registered natural event. Results presented point out that roll waves could have occurred during this already published case-study event. Simulations could predict wave heights within 8% on uncertainty with respect to the mea amplitude of measured waves. Finally a new theoretical solution for the velocity profile is proposed taking into account the porosity of the bed. Results are then compared with numerical simulation performed in FLUENT. A parametric analysis is employed and the case-study is once again evaluated. A: general conclusion, the non-permanent phenomena that can appear during the evolution of a mudflow event affect the overall dynamics of the coupled system (hydraulic-sediment transport) in comparison to the steady and uniform case. Verifying that such phenomena could appear should indeed be an important part in hydraulic engineering projects, especially when dealing with lives, which is the case of mud flows
38
Greaves, Danielle Kathleen. "Désadaptations cardiovasculaires à la microgravité : techniques avancées pour améliorer la mesure et l'évaluation du risque cardiovaculaire induit par les vols spatiaux pour les équipages de longue durée Effects of exercise countermeasure on myocardial contractility measured by 4D speckle tracking during a 21-day head-down bed rest Cardiac and arterial structure and functional changes after four days of dry immersion with and without thigh cuffs Effect of thigh cuff on venous flow redistribution during 4 days in dry immersion." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC433.
Full textAbstract:
L'objectif était de quantifier les modifications de la contractilité cardiaque au cours d’un bedrest de 21 jours (HDBR) par la methode speckle tracking 4D et de déterminer si la contre-mesure « exercice » était capable de préserver cette contractilité cardiaque. Les méthodes traditionnelles 2D ne mesurent qu'une variation de la taille du ventricule de la systole à la diastole et ne suivent pas la cinetique des mouvements de contractilité à l’interieur de la paroi. De plus l’echographie 2D ne permet d’acceder qu’a la contractilite longitudinale globale par la mesure de la distance Apex-Valve mitrale. Le suivi des mouvements des speckles (points singuliers a l’interieur du myocarde) en 4D montre que la contractilité radiale diminuée signifcativement pendant le HDTBR chez les sujets témoins alors qu’elle est conservée dans le groupe exercice. Par contre la contractilité longitudinale n’est pas affectée dans aucun des 2 groupes. Bien sûr, l'IRM pourrait fournir des données similaires, mais il n’est pas possible à ce jour d’imaginer avoir une IRM a bord de l’ISS dans un futur proche. A la suite de ces resultats nous avons mis au point un algorithme de traitement des video cardiaque qui permet d’acceder a la contractilite radiale et longitudinale en vol (prog Vasc-Aging en cours) .L’objectif de l’experimentation était de montrer que quatre jours en immersion seche suffisaient pour realiser un transfert liquidien important vers les régions céphaliques comparable à celui observé en vol spatial. Notre protocole consistait donc a mesurer les volume veineux au niveau cervical cerebral et porte au debut de la periode en immersion (a 2h) puis a 4 jours d’immersion. Compte tenu des problemes engendrés par ce transfert liquidien en vol nous avions proposé de tester la capacité des brassarts de cuisse a reduire l’amplitude du transfert veineux. Les résultats montrent que l’immersion provoque un transfert de sang veineux au niveau cervical maximal à 2H et que les Brassarts de cuisse reduisent signifcativement ce transfert dans cette phase precoce. Par contre a 4 jours d’immersion l’amplitude du transfert sanguin est considerablement diminuée (bien que toujours presente) et les brassarts de cuisse n’ont pas d’effet visible à ce moment-là. En fait le volume plasmatique decroit significativement à la fin du premier jour (env 20%) des lors la masse de sang deplacées vers la tete par l’immersion est insuffisante pour generer une stase importante au niveau cervical comme à 2h d’immersion. Pour cette meme raison la vitesse dans les veines cerebrales n’est pas augmentée à 4 jours d’immersion contrairement à ce qu’on avait observé à 2h d’immersion lors d’une precedente etude. Donc le modele immersion seche est un modele pour etudier les transferts liquidiens en microgravité mais seulement en debut de phase d’immersion. Sur cette période de temps, les Brassarts de cuisse ont bien un effet protecteur pour les organes de la zone cephaliqueObjective: to evaluate functional myocardial contractility after 21 days of head-down bed rest (HDTBR) in sedentary control (CON) or with a resistive vibration exercise (RVE) countermeasure (CM) applied, by using 4D echocardiographic (4D Echo) imaging and speckle tracking strain quantification.Methods: Twelve volunteers were enrolled in a crossover HDTBR design, and 4D Echo was performed in supine position (REST) at BDC-2 and at R+2, and in -6° HDTBR (on day 18), and also during the first and the last minute of the 80° head-up step of Standard Measures tilt test, performed at both BDC-2 and R+2. Radial (Rad-Str), longitudinal (Lg-Str) and twist (Tw-Str) strain were measured by 4D speckle tracking, as well as left ventricle diastolic volume (LVDV) and mass (LVmass).Results: On day 18: in the CON group, LVDV and LVmass were reduced (p<0.05), the Rad-Str decreased (p<0.05) and Tw-Str showed a tendency to increase (p< 0.11), with no changes in Lg-Str. In RVE group, LVDV and LV mass, as well as all the strain parameters remained unchanged.On R+2: in the CON group, LVDV and LVmass were not recovered in all subjects compared to pre-HDTBR (p<0.08), Rad-Str was still decreased (p<0.05), while Tw-Str tended to increase (p<0.09). These parameters remained unchanged in the RVE group.Tilt 80°: Rad-Str and Lg-Str values at 80° tilt were similar post HDT in both groups.Conclusion: 4D Echo and speckle tracking analysis showed that in the CON group, Rad-Str decreased concomitant with LVmass and LVDV with HDTBR, but this observation did not support the hypothesis that this HDTBR induced remodelling or a muscle atrophy. RVE acted to preserve both LVmass, LVDV and contractility during HDTBR, thus proving its effectiveness to this aim. Nevertheless, the significant HDTBR-induced changes observed in the CON group had only a limited effect on the cardiac contractile response as observed during post HDTBR tilt test. The level of contractility at 80° Tilt position was not affected neither by HDTBR nor by RVE CM.Purpose: The objective was to quantify the venous redistribution during a 4-day dry immersion (DI) and evaluate the effect of thigh cuffs.Methods: The study included 9 control (Co) and 9 subjects wearing thigh cuffs during daytime hours (CU). Ultrasound images were collected Pre DI, on the fourth day in the morning (D4 AM) and on the fourth day in the afternoon (D4 PM), to assess the following outcome variables: left ventricle dimension, stroke volume, and ejection fraction (LVD, SV, EF), jugular vein volume (JV), portal vein dimension (PV), middle cerebral vein velocity (MCVv). An additional measure of JV dimension was performed on the first day after having worn the cuffs for two hours (D1 2H).Results: The JV volume increased significantly from Pre to D1 2H in both groups, but increased more in the Co compare to the CU subjects (Co: 0,27+/0.15cm3 to 0.94+/-0;22 cm3;P<0.01 CU: 0,32+/-0.13 cm3 to 0.64+/-0.32 cm3 P<0.042).At D4 AM no difference was found between the two treatment groups for any of the parameters listed above.Stroke volume and EF decreased from Pre (SV:111+/-23cm3 to 93+/-24 cm3 p<0.05; EF:0.66+/-0.07 to 0.62+/-0.07 p<0.05). JV volume was slightly, but significantly increased (Co: 0.47+/-0.22cm3 CU:0.35+/-014cm3 P<0.05), while MCVv and PV remained unchanged from Pre DI. From D4 AM to PM these parameters did not show any significant change.Conclusion: The results confirm that DI induces, during the first 2-3 h, a significant cephalic fluid shift as observed in spaceflight. During this early phase the thigh cuffs reduced the amplitude of the fluid shift towards the head, but after 4 days in DI there was only a slight memory (residual) effect of DI on the jugular volume and no residual effect of thigh cuffs
39
Brocheray, Sandra. "Transferts et accumulations sur les marges du Golfe de Gascogne : architecture, fonctionnement et contrôles." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0079/document.
Full textAbstract:
Ce travail présente une analyse de la morphologie et de la dynamique sédimentaire des systèmes turbiditiques actuels du Cap-Ferret et de Capbreton (sud du Golfe de Gascogne). La reconnaissance effectuée sur le système de Capbreton est la première à le considérer dans son ensemble. Ce travail se base sur des données acoustiques de subsurface (sondeur multifaisceaux, sondeur de sédiments Chirp) et de carottages issues de la campagne océanographique Sargass menée par l’Université de Bordeaux. L’analyse morpho-bathymétrique révèle l’organisation amont-aval des géométries sédimentaires dans ces systèmes et, couplée aux données sédimentaires, de préciser les processus de dépôts liés aux écoulements gravitaires. Le fonctionnement holocène du canyon de Capbreton montre des processus gravitaires haute fréquence, révélant son rôle de dépôt-centre pour le sud du golfe de Gascogne. Dans le système du Cap-Ferret, la zone de transition chenal-lobe a été investiguée à fine échelle, documentant ainsi des structures sédimentaires rarement identifiées avec ce niveau de détails dans les systèmes turbiditiques modernes. La dynamique sédimentaire de chacun de ces systèmes est soumise à des forçages auto-cycliques et glacio-eustatiques qui affectent chacun des systèmes de façons différentes. Ces informations ont permis de proposer un modèle régional de fonctionnement sédimentaire au cours des derniers 50 000 ansThis work presents an analysis of the morphology and sedimentary dynamic of the Cap-Ferret and Capbreton turbidite systems (south Bay of Biscay), containing the first recognition of the whole Capbreton turbidite system. The dataset comprises subsurface geophysical data (multibeam bathymetric and imagery, Chirp sub-bottom profiler) and piston cores, acquired during the oceanographic cruise Sargass conducted by the Bordeaux University. Studied by morpho-bathymetric analyses, the upstream-downstream evolution of the sedimentary bodies joined to the sedimentological data help to understand the active gravity processes of the systems. In the Capbreton system, a special focus is made on its Holocene gravity deposits occurring at high frequencies. In the Cap-Ferret system, the channel-lobe transition zone has been investigated at high resolution and revealed sedimentary structures poorly documented at this scale of details in recent turbidite systems. The glacio-eustatic and autocyclic forcing are expressed in different ways in each turbidite sytem. A regional sedimentary dynamic model is proposed for the last 50,000 years
40
MALANDRA, FRANCESCO. "Land use/cover shifts and wildfires as drivers of mountain forest landscape dynamics in the Apennines (Italy)." Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274504.
Full textAbstract:
Con questa tesi di dottorato sono state studiate le dinamiche di paesaggio dell’Italia peninsulare legate a processi di cambiamento di copertura/uso del suolo e ai recenti incendi, nel contesto del cambiamento climatico in atto. I cambiamenti di uso del suolo sono stati analizzati principalmente nelle aree montane dell’intero arco appenninico, mentre gli effetti sul paesaggio di due recenti e rilevanti stagioni di incendi sono stati analizzati estendendo l’area di studio all’Italia peninsulare e alle due isole maggiori (Sardegna e Sicilia). In primo luogo, abbiamo ritenuto appropriato l’utilizzo di una meta-analisi come strumento preliminare di sintesi di dinamiche eterogenee evidenziate da molteplici casi di studio situati su un’ampia area geografica, poiché la ricerca in materia adotta solitamente un approccio basato sul singolo caso di studio nell’analisi del cambiamento. Dopo aver selezionato 51 articoli pubblicati e 57 relativi casi di studio, abbiamo esaminato i dati e standardizzato la metodologia di trattamento degli stessi per ottenere una nuova serie di dati omogenei per un’analisi comparativa delle dinamiche di paesaggio. Il passo successivo è stato quello di adottare una metodologia standard di campionamento di repliche di paesaggi per quantificare i cambiamenti a scala regionale. Abbiamo selezionato 10 siti rappresentativi lungo l’Appennino e studiato i cambiamenti di copertura e di struttura del mosaico paesaggistico confrontando diverse esposizioni (Nord-est vs Sud-ovest) e fasce altitudinali (bassa vs alta quota) e analizzando i fattori principali che influenzano le dinamiche bosco/non-bosco. I recenti cambiamenti di uso/copertura del suolo e del clima presso tutto il bacino del Mediterraneo hanno stanno alterando il regime storico di incendi e portando all’aumento della loro frequenza, superfice e severità. Nell’ultimo capitolo, abbiamo creato un database di grandi incendi forestali (> 100 ha) attraverso tecniche di telerilevamento e specifici criteri di selezione, al fine di studiare le caratteristiche, la severità e gli effetti sul paesaggio di due rilevanti stagioni di incendi forestali (2007 e 2017) nell’Italia peninsulare e principali isole. I risultati preliminari ottenuti offrono un quadro comparativo delle caratteristiche di grandi incendi di annate particolarmente siccitose, che si stima saranno sempre più frequenti nel contesto del cambiamento climatico in atto.This research aimed to study landscape dynamics along the Italian peninsula, due to land use/cover shifts and recent wildfires, within the contest of climate change. Land use changes were mainly focused on the mountain areas along the whole Apennines range, whereas the landscape effects of two recent and extreme fire seasons were assessed along the Italian peninsula and the two major islands (Sardinia and Sicily). Firstly, we considered a meta-analysis an appropriate and preliminary tool for summarizing general patterns and heterogeneous findings from several case-studies over a large geographic area, since land-use science usually adopts the case-study approach to investigate landscape changes. Out of 51 published articles and different databases that referred to 57 case-studies, we explored heterogeneous data sets and standardized the processing methods to obtain a new set of homogeneous data for a comparative landscape change analysis. Secondly, we used a replicate landscape approach and a systematic sampling design for quantifying changes at regional scale. We selected 10 representative sites located along the Apennines and investigated land-cover changes and landscape configurational shifts comparing different slope aspects (North-East vs South-West slopes) and altitudinal zones (low elevation vs high elevation) and assessing the main drivers of the non-forest/forest dynamics. Recent changes of land use/cover and climate in the Mediterranean basin altered historical fire regimes and led to an increase of the frequency, area and severity of wildfires. In the last chapter, we created a dataset of large wildfires (>100 ha) using remote sensing techniques and adopting specific selection criteria in order to study the occurrence, the severity and the landscape effects of two major forest fire seasons (2007 and 2017) in peninsular Italy and Sicily and Sardinia islands. Preliminary results offer a comparative picture of large fire features in dry years which are expected to occur more frequently in a climate change scenario.
41
Wei, Wei. "Characteristics of the late Mesozoic tectonic evolution of the South China block and geodynamic implications : Multi-approach study on the Qingyang-Jiuhua, Hengshan and Fujian coastal granitic massifs." Phd thesis, Université d'Orléans, 2013. http://tel.archives-ouvertes.fr/tel-01058791.
Full textAbstract:
The vast distribution and long duration of the Late Mesozoic magmatism in the eastern part of South China presents a unique case in the world. This offers a natural laboratory to study the process of magma genesis, the magma emplacement mode, the relationship between magmatism and tectonics, the geodynamic role on the magma emplacement and lithospheric evolution. Since 50's, particularly 90's of the last century, geoscientists have made important efforts in geological cartography and carried out numerous studies with remarkable scientific achievements, building a solid background to understand the tectonic evolution of the South China Block (SCB). However, certain fundamental questions mentioned above remain unsolved and/or are in hot debate. In order to make progress in these scientific issues, we have carried out in a multi-disciplinary study in the Late Mesozoic Qingyang-Jiuhua massif, Hengshan massif and Fujian coastal zone according to their distance with respect to the paleo subduction zone of the Paleo-Pacific plate, the ages of granitic massifs and related tectonics, including field observation on the structure geology, micro-observation on thin section, U-Pb dating on monazite, AMS, paleomagnetism, gravity modeling and P condition concern the granite emplacement. In the view of deformation in these granitic massifs and their country rocks, mode and influence of regional tectonics on the emplacement, though each studied zone reveals its distinguished characteristics, they show some intrinsic and common relationships between them. With our new results and integrating previous data, in this thesis, we discuss the tectonic context of emplacement of these Late Mesozoic magmatic massifs and the geodynamic evolution of the SCB., We propose a 3-step geodynamic model: (1) during 145-130 Ma period, the Paleo-Pacific plate subducted northwestwardly, the West Philippines micro-continent, approaching to SCB, important subduction-related arc volcanism was produced in the coastal areas of Southeast China coast (Zhejiang-Fujian-Guangdong), forming a back-arc extension tectonic system in SCB; (2) during 130-110 Ma period, due to the collision between the West Philippines microcontinent and SCB, the compressional tectonic structures were developed in the Changle-Na'ao coastal zone, producing ductile deformation zones. However, the inland of the eastern part of SCB was under a NW-SE extensional tectonic regime; (3) during 105-90 Ma period, a new subduction zone was developed in the SE flank of the West Philippines micro-continent, the subducting slab reached the Changle-Nan'ao tectonic belt, with the possible break-off of slab, the asthenospheric ascent was responsible for the important emplacement of plutonic massifs and dykes. The tectonics of the eastern part of SCB was characterized by a general extensional system in this period. This tectonic pattern has been significantly disturbed by the Oligocene-Eocene opening of the South China sea,and the Miocene shortening of the SCB margin in Taiwan. Of course, this model should be improved by more geological, geophysical and geochemical investigations.
42
Cheng, Tze-Chiang, and 程自強. "Gravity Changes in Taiwan：Observations and Analysis." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/37qb2t.
Full textAbstract:
博士國立交通大學
土木工程系所
101
The temporal gravity changes in Taiwan are used to examine the crustal deformation in Taiwan. All gravity observations are corrected by the environmental effects, such as solid earth tide, ocean tide loading, polar motion, atmosphere and underground water. This study will put a special emphasis on ocean tide loading. Ocean tide loading(OTL) effect of gravity is large in Taiwan and around its nearby area. Three different OTL models are tested to improve the accuracy of absolute gravity around the coast of Taiwan and its islets. The model SGOTL with the latest regional ocean tide model of Taiwan is assimilated with local tide gauge records. In Taiwan, OTL10 and the high resolution DEM result in the optimum accuracy in the OTL corrections of absolute gravity measurements. It’s obviously to shown the standard deviations of adjusted gravity have reduced by using mixed method of ladder and star. Two major relative network campaigns around the whole Taiwan are made from 2003 to 2007. The relative gravity observations are adjusted using the weight-constraint least-squares method. With the 4-year gravity changes, we have found that orogeny occurs on the central ridges and land subsidence occurs in southwestern Taiwan with average rates of -0.085 mgal/year and 0.061 mgal/year, respectively. A gravity network in the Yunlin County in western Taiwan is established to determine gravity variations caused by large land subsidence. At station TAES, the gravity change rate from absolute measurements by FG5 is 22.72 μgal/year. The gravity-height admittance factor in Yunlin subsidence area is -5.25 μgal/cm, instead of -1.97 μgal/cm, due to the complicated mechanism of subsidence. This result can be a prototype method of subsidence monitoring by gravimetry.
43
Kao, Yu-Chi, and 高豫麒. "Gravity and hydrological changes from satellite altimetry and satellite gravimetry." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/23139656104979703042.
Full textAbstract:
博士國立交通大學
土木工程學系
98
The main research topics of this study are : (1) to determine changes of sea surface heights and oceanic mass using satellite altimetry (SA) and steric heights, and to determine the contributions of such changes to variations of geocenter, J2, and polar motions. (2) to determine lake level changes using SA and Gravity Recovery and Climate Experiment (GRACE) gravimetry data. Using SA and steric heights over October 1992 to December 2007, the following results are obtained : (1) the rates of sea level anomaly (SLA), steric height anomaly and corrected SLA (CSLA) are 2.94 ± 0.18, 0.32 ± 0.28 mm/yr and 2.47 ± 0.14 mm/yr. (2) The trends of CSLA, SLA and steric heights are conflicting over some oceanic areas, suggesting that large uncertainties of the underlying data may exist here. (3) The rate, annual amplitude and phase of , which is the oceanic mass-induced variation of the zero-degree geopotential coefficient, are 1.16 ± 0.07 × 10-10, 5.1 3 × 10-10 and -81.2º. (4) The rates of the geocenter variations in x, y, and z are -0.105 ± 0.015, 0.011 ± 0.019 and -0.234 ± 0.015 mm/yr. (5) The rate and annual amplitude and phase of J2 are 0.57 ± 0.08 × 10-11/yr, 1.98 × 10-11/yr and -127.21∘. (6) The magnitude of is 3 times greater than that of , suggesting that the oceanic mass contributes more to the x component of the polar motion than the y component. Using the variations of lake level from SA and the equivalent water heights (EWH) from the monthly GRACE gravity fields and the Climate Prediction Center (CPC) hydrological model, it is estimated that about 60% and 30% of water in the catchment areas of Lakes Baikal and Balkhash enter these two lakes. The phase of the annual variation of the Baikal lake level from GRACE differ by 7 months from the phases obtained with satellite altimetry and the CPC model. This difference is due to a climate factor and some man-made causes. Monthly temperature data over two time periods around Lakes Baikal and Balkhash show that the mean temperature in the earlier period is larger than that in the later period. On average, temperatures over Baikal and Balkhash increase by 0.64° and 0.7°C. Over these two periods the mean temperature around Baikal changes from sub-zero to above-zero, suggesting that the permafrost here may thaw to increase the amount of water entering Baikal. A common feature in the trends of J2 and the lake levels of Baikal and Balkhash is that the trend before the 1997-1998 El Niño is reversed after this event.
44
Lin, Ting-Jung, and 林廷融. "Temporal Gravity Changes from FORMOSAT-3 and GRACE GPS Tracking Data." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98725633081021016379.
Full textAbstract:
博士國立交通大學
土木工程學系
98
This dissertation is aimed at temporal gravity field recovery from the analyses of the high-low satellite-to-satellite tracking (hl-SST) data from the COSMIC and GRACE satellite missions. In order to estimate the time-varying geopotential coefficients, two efficient methodologies, the analytical orbital perturbation (AOP) approach and the residual acceleration (ACC) approach, are developed in the research. With the reference orbits removed, orbital perturbations (difference between kinematic and reference orbits) and residual accelerations (difference between observed and reference accelerations) from the residual orbits are linear functions of the time-varying geopotential coefficients. Such linear functions enable convenient establishments of observation equations to estimate geopotential coefficients. The Bernese 5.0 software is used to compute the cm-level kinematic orbits of COSMIC and GRACE. The NASA Goddard’s GEODYN II software is used to compute the perturbing forces acting on COSMIC and GRACE satellites based on the standard models of orbit dynamics. The accelerations due to the atmospheric drag, solar radiation pressure and other minor surface forces are estimated by some relevant model parameters over one orbital period from COSMIC’s kinematic and reduced dynamic orbits. The 5s kinematic and dynamic orbits from six COSMIC and the 10s orbits from two GRACE satellites are re-sampled into 1 minute normal point positional data and then converted to acceleration data by numerical differential for gravity recovery. To validate the theories and computer programs associated with the AOP and ACC approaches, some experimental solutions of time-varying geopotential coefficients are carried out using one-month (August 2006) of COSMIC and GRACE kinematic and dynamic orbits. The average RMS in RTN directions of reduced COSMIC and GRACE (1 minute) between kinematic orbits and dynamic orbits are about 7.5 and 6.5 cm. The COSMIC solutions reveal several well-known temporal gravity signatures, but contain artifacts. The combined COSMIC-GRACE solutions enhance some local features in the GRACE solutions. The monthly COSMIC and GRACE precise orbit data from September 2006 to December 2007 (16 months) are processed to recover monthly low-degree (up to degree 5) geopotential coefficients by the AOP and ACC approaches. The geoid variations from such low-degree geopotential coefficients are compared with the CSR RL04 solutions. Two combined solutions by the AOP and ACC approaches (up to degree 15) are also carried out. The monthly variations of the zonal geopotential coefficients, the AOP and ACC solutions (degree 5) closely resemble the SLR-derived and CSR RL04 solutions.
45
CHEN, KUAN-HUNG, and 陳冠宏. "Estimation of aquifer specific yields by gravity changes at multiple time scales." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/37bhg5.
Full textAbstract:
博士國立交通大學
土木工程系所
107
Specific yield (Sy) is the ratio of drainable groundwater in an unconfined aquifer and also a key parameter for evaluating the storage of an underground reservoir. Conventionally, Sy is obtained by pumping tests which manually create a small scaled groundwater level change, but the high cost of well construction restricts the well numbers in the field. Groundwater level change will introduce gravity and land surface change, which can be used to estimate Sy and storage coefficient (S) by the geodetic method. Earlier studies for the geodetic method are largely based on simulated gravity and surface changes. In comparison, this study focuses on field measurements of gravity and surface change to determine these aquifer coefficients using precision gravimeters and levels at time scales ranging from hours to years. For short-time scales, we used a precise level and absolute gravimeter to detect the land surface change and gravity change during several pumping tests in Taiwan. At the Neicheng pumping test site, the geodetic method results in S=2.97×10-4 and Sy =0.20, which are consistent with the pumping test result. For the median time scale of Sy determination, we used a post-rain aquifer recession that introduced declines in groundwater levels and in gravity values at Shinming. These groundwater level and gravity change result in Sy =0.16, which is close to the Sy value at a nearby pumping test site. For the long time scale, we established 10 absolute gravity sites over the upper Choushui River Alluvial Fan (CRAF) and Mingchu basin (MCB), where we measured 40 successive gravity changes to estimate Sy values over several seasons from 2015 to 2017. The estimated Sy values range from 0.04 to 0.28, which are consistent with those determined by the hydraulic method which ranges from 0.03 to 0.24. The result from this study suggests that the sequentially uplift and decline of groundwater levels work much like pumping and injection test at the same segment of an aquifer, which can be sensed by a precise gravimeter. This gravity method (the geodetic method that uses gravity changes) is cost-effective and can produce reliable Sy values using successive groundwater and gravity changes between seasons. At most of the gravity sites in the CRAF and MCB, the gravity method produced almost the same Sy values from groundwater and gravity changes spanning wet and dry seasons in different years, suggesting that this method is operational and reliable for Sy determination, as the hydraulic method. The gravity method is not affected by the heterogeneity of an aquifer that can damage the result from the hydraulic method. The study discusses the limitations and advantages of the geodetic method in estimating aquifer storage coefficients in the field. The lessons of the gravity field work from this study contribute to assessing the feasibility of the geodetic method at a given site.
46
Enos, Robert A. "Changes in gravity anomalies during erosion and isostatic rebound of collisional mountain ranges." Thesis, 1992. http://hdl.handle.net/1957/36718.
Full textAbstract:
At collisional mountain ranges the tectonic history of crustal shortening and
subsequent post-collisional erosion is preserved in the form of the presently observed
gravity anomalies. In this study, models of erosion and isostatic rebound at various stages
of collision illustrate the evolution of crustal structure, topography, and resulting gravity
anomalies.
The Ouachita Mountains of Arkansas, which show a low/high Bouguer gravity
couple characteristic of the initial stages of collision, have undergone just 8 km of erosion
during the process of completely rebounding the syn-orogenic crustal root. This minor
rebound means that the Ouachitas retain a crustal geometry similar to the continental margin
prior to collision, including thin transitional and oceanic crust.
At more advances stages of collision Bouguer gravity anomalies show a broad low
reflecting a thickened crustal root. The width of this low, which relates directly to the
amount of crustal shortening, is retained during subsequent erosion and elastic rebound,
but the amplitude decays gradually. Thus, the width and amplitude of the low can be used
to estimate the degree of convergence and amount of erosion, respectively, for a specific
mountain range. For the Scandinavian Caledonides results are consistent with 20 km of
erosion following 200 km of crustal shortening. Following a larger magnitude of
convergence, about 300 km, the southern Appalachians are estimated to have undergone
28 km of post-collisional erosion. Bouguer gravity profiles across the recently-active Alps
compare with a model of 200 km of crustal shortening and 8 to 12 km of erosion. While
the Alps have undergone a similar amount of shortening as that estimated for the
Caledonides, erosion and post-collisional rebound is at an initial stage, such that a thick
section of exotic crust still overlies the underthrusted European Platform.
The results of these model comparisons suggest that the crustal geometry ofa
collisional mountain range should be viewed as a consequence of the degree of crustal
shortening as well as the amount of erosion and isostatic rebound. In models at moderate
to advanced stages of shortening ( 200 km), and mature stages of erosion (e.g.,
Caledonides, Appalachians), the geometry of the crustal "suture" between overthrusting
and underthrusting crusts is present as a shallow, subhorizontal de collement beneath the
foreland. In the hinterland the suture abruptly steepens, a result of differential uplift during
isostatic rebound. This crustal geometry, characteristic of seismic-reflection profiles
across many ancient mountain belts, suggests: (1) that the "low angle detachment"
observed beneath collisional mountain ranges was originally much deeper and steeper than
it is at present; and (2) that steep-dipping seismic reflectors towards the hinterland represent
the thrusted contact between converging crustal blocks, but have been steepened as a result
of isostatic uplift following erosion.Graduation date: 1992
47
Lin, Yu-siang, and 林榆翔. "Comparing the GRACE satellite with land hydrology to explore gravity changes in Taiwan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/99485166256026321989.
Full textAbstract:
碩士國立中央大學
地球物理研究所
100
In this study we use the GRACE satellite gravity data provided by CSR, of which the GSM version has already had the non-tidal atmosphere and oceans components removed. The highest spherical harmonic degree is 60, corresponding to around 333 kilometers of spatial resolution. We take the point (E121°, N23°45‘) near the central part of Taiwan to represent the whole Taiwan. The GRACE data of gravity changes have relationship with surface water cycle through the surface water balance equation：ΔS/Δt=P-E-R, where ΔS means change in storage converted from GRACE gravity data to the equivalent depth, P means precipitation, E means evapotranspiration, and R means runoff. For P we employ the data of precipitation from the Central Weather Bureau by means of Thiessen Polygons Method. E is modled via the Hamon (1979) algorithm using temperature data. R is obtained from the Water Resources Agency statistics. Comparing between ΔS and P-E-R can help understand the precision of the GRACE Satellite measurement for Taiwan, as well as analyze further the phenomena of surface water cycle in Taiwan. The results show that the correlation is low between the GRACE satellite measurements and the P-E-R. The main reason is Taiwan''s high terrain, steep slope and rapid runoff, resulting rainfall can not stay long on land.
48
Setiawan, Ari [Verfasser]. "Modeling of gravity changes on Merapi Volcano : observed between 1997 - 2000 / von Ari Setiawan." 2003. http://d-nb.info/968772501/34.
Full text
49
Phillips, Kristen Michelle. "Modeling within-tree changes in wood specific gravity and moisture content for loblolly pine in Georgia." 2002. http://purl.galileo.usg.edu/uga%5Fetd/phillips%5Fkristen%5Fm%5F200205%5Fms.
Full text
50
Lederman, Jerusha Isabel. "Structural changes of the Quasar 3C454.3 used as an extragalactic reference source for the gravity Probe B Mission /." 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:MR19684.
Full textAbstract:
Thesis (M.Sc.)--York University, 2006. Graduate Programme in Earth and Space Science.Typescript. Includes bibliographical references (leaves 148-150). 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:MR19684