This dissertation is focused on a study of selected environmental effects influencing terrestrial gravity observations. Global geopotential models were used to compute quantities of the disturbing gravity field and its variations during time period. Furthermore, analyses of an atmospherical and hydrological effects on the gravity observations were provided. The computation was realized at the station Pecný, however the concept was proved and compared with data from station Strasbourg. Consequently, the results were discussed with respect to quasigeoid modelling established from gravity and astrogeodetic measurements. The result and recommendations for future research are exposed.

The focus of this thesis is development of an electronic subsystem for reduced gravity impact simulator. The research part of this thesis firstly covers methods used for simulation of microgravity or reduced gravity and compares them. Another part of research focuses on three selected potential approaches to creating the electronic subsystem for this device. The second, practical, part of this thesis describes the design and development of the electronic subsystem. The foundation of the electronic subsystem is a control unit which has been developed on the basis of an STMicroelectronics microcontroller. Using the control unit, the electronic subsystem measures pressure, position, acceleration and force in the system. Another task of the control unit is control of a stepper motor. Integration of individual elements into the electronic subsystem is described both in terms of software and hardware. Furthermore, a graphic user interface program for PC has been developed as a means to interact with the system. In the final part of the thesis, the operation of the electronic subsystem is described and lastly, the electronic subsystem is evaluated.

With the help of MERRA-2 (Modern-Era Retrospective Analysis for Research and Application, version 2) reanalysis data of the zonal wind, measurements of the mesopause region wind over Collm by low-frequency observations, and data of the Horizontal Wind Model, a height profile for the zonal wind in January and July was created by linear interpolation over altitude. Subsequently, three different 5-year periods (1980-1984, 1994-1998 und 1999-2003) were selected, and the obtained wind profiles and NRLMSISE (Naval Research Labatory Mass Spectrometer Incoherent Scatter, Extended) temperatures (January and July) were averaged over these time intervals. This allowed to run the whole atmosphere nonlinear spectral gravity wave (GW) routine of Yiğit et al. (2008) with these data as background profiles. We obtained a height profile of the GW momentum flux (MF) over these three 5-year periods. Based on this, the long-term tendencies of GW MF are estimated and in this way a statement about the trend of the GW activity in the mesosphere and lower thermosphere can be made. GW MF increases in magnitude in both summer and winter. The results are in qualitative agreement with trends of GW proxies obtained from the meteor radar measurements at Collm. / Mit Hilfe von MERRA-2 - Reanalysedaten des Zonalwindes, Messungen des Meteorradars in Collm und mit Daten des Horizontal Wind Models wurde durch lineare Interpolation ein Höhenprofil für den Zonalwind für die Monate Januar und Juli erstellt. Anschließend wurden aus den gewonnenen Windprofilen und NRLMSISE (Naval Research Labatory Mass Spectrometer Incoherent Scatter, Extended) Temperatur Reanalysen (Januar und Juli) drei verschiedene 5-Jahreszeiträume gewählt (1980-1984, 1994-1998 und 1999-2003) und über diese gemittelt. Diese Daten wurden als Hintergrund für die nichtlineare spektrale Schwerewellenroutine nach Yiğit et al. (2008) verwendet, wodurch der Schwerewellenfluss über die drei 5-Jahreszeiträume bestimmt werden konnte. Aus diesen Analysen ließ sich nun der Trend zwischen den jeweiligen Zeiträumen berechnen und so eine Aussage über den Trend der Schwerewellenaktivität in der Mesosphäre und unteren Thermosphäre ableiten. Die Ergebnisse zeigen gute Übereinstimmungen zu anderen Forschungsergebnissen bzgl. der Trends der GW Proxies von Meteorradarmessungen in Collm.

The state gravity maps of Oregon and Washington show a gravity high centered south of Portland, Oregon and a gravity low in the Tualatin Valley to the west disrupting the regional gravity gradient which is controlled by crustal thickening. Detailed gravity surveys done in the Portland area are consistent with the state gravity maps but show considerably more detail. Quantitative interpretation of this data has provided new information on the subsurface structure in this area; recent work has yielded corroborative evidence for a fault zone bounding the east side of the Portland Hills, and has indicated the presence of faults under the Portland Basin to the east which were previously unknown.

This study investigates the influence of the gravity load resisting system on the collapse performance of Special Steel Moment Frames (SMFs). The influence was quantified using the FEMA P-695 methodology. The buildings used for this study were a 2-, 4- and 8-story SMFs taken from the ATC76-1 project where their collapse performance was already evaluated without the gravity system. The main work of this dissertation has been divided in two parts. The first part studies the influence of the gravity system when it is incorporated explicitly as part of the lateral resisting system. Aspects of the gravity frame that were investigated include the contribution of stiffness and strength of beam to column connections, and the location of splices in the gravity columns. Moreover, this research investigates the potential for the development of inelastic deformations in the gravity columns, and the effect of such deformations on structural response. The results show that gravity connections and gravity column's continuity profoundly affect the computed response and collapse probability. The inelastic behavior in gravity columns has a less important effect but should be included in the analysis. The second part of the investigation looks more in depth at the role of the gravity columns on the collapse performance of SMFs. Using the 2-, 4- and 8-story SMFs, the gravity columns are incorporated using the approach where all the gravity columns are lumped into one elastic, pinned at the base and continuous element. The approach is first validated by checking different aspects such as: strength of gravity connections to induce yielding into gravity columns, difference between the explicit and lumping column approach, and required gravity column's splices to provide continuity. The stiffness of the element representing the gravity columns was varied in order to find the influence of the gravity columns. At the end of the study it was found that they have a significant influence on the collapse performance of SMFs, especially on taller structures like the 8-story model. Moreover it was concluded that an adequate stiffness of the gravity columns could be found by performing nonlinear static pushover analysis. / Ph. D.

No description available.

No description available.

An interpretation of gravity and magnetic anomalies of the Butte district, Montana, is based on the analysis of five gravity profiles constructed from Bouguer gravity data of the Butte district observed during the summer of 1974 and give concurrent magnetic profiles constructed from U.S. Geological Survey high-level aeromagnetic data of the district. Of primary concern in this analysis is the interpretation of the Bouguer gravity high and aeromagnetic low associated with the Butte orebody. Results of this interpretation yield a configuration for the Butte orebody characterized by vertical contacts extending from the surface or directly beneath Cenozoic basin fill to 4,500 feet below sea level, with a central core, elongate in the north -south direction, surrounded by a variable outer zone, which is more pronounced in the southern and western portions of the district. The central core is interpreted as a region of zero magnetic susceptibility with three density distributions, all of which are of higher densities than the surrounding host rock and are related to the varying degrees of mineralization and alteration present in this region. The laterally variable outer zone is interpreted as a zone of low magnetic susceptibility with a density equal to that of the host rock. This zone is related to the peripheral mineralization and alteration of the Butte orebody.

This dissertation consist of three parts. The first part of the thesis is devoted to the study of gravity and higher spin gauge theories in 2+1 dimensions. We construct cosmological so-lutions of higher spin gravity in 2+1 dimensional de Sitter space. We show that a consistent thermodynamics can be obtained for their horizons by demanding appropriate holonomy conditions. This is equivalent to demanding the integrability of the Euclidean boundary CFT partition function, and reduces to Gibbons-Hawking thermodynamics in the spin-2 case. By using a prescription of Maldacena, we relate the thermodynamics of these solutions to those of higher spin black holes in AdS3. For the case of negative cosmological constant we show that interpreting the inverse AdS3 radius 1=l as a Grassmann variable results in a formal map from gravity in AdS3 to gravity in flat space. The underlying reason for this is the fact that ISO(2,1) is the Inonu-Wigner contraction of SO(2,2). We show how this works for the Chern-Simons actions, demonstrate how the general (Banados) solution in AdS3 maps to the general flat space solution, and how the Killing vectors, charges and the Virasoro algebra in the Brown-Henneaux case map to the corresponding quantities in the BMS3 case. Our results straightforwardly generalize to the higher spin case: the flat space higher spin theories emerge automatically in this approach from their AdS counterparts. We also demonstrate the power of our approach by doing singularity resolution in the BMS gauge as an application. Finally, we construct a candidate for the most general chiral higher spin theory with AdS3 boundary conditions. In the Chern-Simons language, the left-moving solution has Drinfeld-Sokolov reduced form, but on the right-moving solution all charges and chemical potentials are turned on. Altogether (for the spin-3 case) these are 19 functions. Despite this, we show that the resulting metric has the form of the “most general” AdS3 boundary conditions discussed by Grumiller and Riegler. The asymptotic symmetry algebra is a product of a W3 algebra on the left and an affine sl(3)k current algebra on the right, as desired. The metric and higher spin fields depend on all the 19 functions. The second part is devoted to the problem of Neumann boundary condition in Einstein’s gravity. The Gibbons-Hawking-York (GHY) boundary term makes the Dirichlet problem for gravity well defined, but no such general term seems to be known for Neumann boundary conditions. In our work, we view Neumann boundary condition not as fixing the normal derivative of the metric (“velocity”) at the boundary, but as fixing the functional derivative of the action with respect to the boundary metric (“momentum”). This leads directly to a new boundary term for gravity: the trace of the extrinsic curvature with a specific dimension-dependent coefficient. In three dimensions this boundary term reduces to a “one-half” GHY term noted in the literature previously, and we observe that our action translates precisely to the Chern-Simons action with no extra boundary terms. In four dimensions the boundary term vanishes, giving a natural Neumann interpretation to the standard Einstein-Hilbert action without boundary terms. We also argue that a natural boundary condition for gravity in asymptotically AdS spaces is to hold the renormalized boundary stress tensor density fixed, instead of the boundary metric. This leads to a well-defined variational problem, as well as new counter-terms and a finite on-shell action. We elaborate this in various (even and odd) dimensions in the language of holographic renormalization. Even though the form of the new renormalized action is distinct from the standard one, once the cut-off is taken to infinity, their values on classical solutions coincide when the trace anomaly vanishes. For AdS4, we compute the ADM form of this renormalized action and show in detail how the correct thermodynamics of Kerr-AdS black holes emerge. We comment on the possibility of a consistent quantization with our boundary conditions when the boundary is dynamical, and make a connection to the results of Compere and Marolf. The difference between our approach and microcanonical-like ensembles in standard AdS/CFT is emphasized. In the third part of the dissertation, we use the recently developed CFT techniques of Rychkov and Tan to compute anomalous dimensions in the O(N) Gross-Neveu model in d = 2 + dimensions. To do this, we extend the “cow-pie contraction” algorithm of Basu and Krishnan to theories with fermions. Our results match perfectly with Feynman diagram computations.

Dans cette thèse nous explorons les aspects de la gravité d'Einstein qui sont propres à la dimension quatre.L'une des propriétés surprenantes liées à cette dimension est la possibilité de formuler la gravité de manière 'Chirale'. Dans ce type de reformulations, typiquement, la métrique perd son rôle centrale. La correspondance entre espace-temps et espace des twisteurs est un autre aspect propre à la dimension quatre. Ces formulations, Chirale et Twistorielle, semblent très différentes. Dans la première partie de cette thèse nous montrons qu'elles sont en fait intimement liées: en particulier nous proposons une nouvelle preuve du `théorème du graviton non-linéaire', due à Penrose, dont le cœur est la géométrie des SU(2)-connections (plutôt qu'une métrique). Dans la seconde partie de cette thèse nous montrons que la gravité en trois et quatre dimensions est liée à des théories d'une nature complètement différentes en dimension six et sept. Ces théories, due à Hitchin, sont des théories de trois-formes différentielles invariantes sous difféomorphismes. En dimensions sept, nous rencontrons seulement un succès partiel puisque la théorie 4D qui en résulte est une version modifiée de la gravité. Cependant nous prouvons au passage que les solutions d'une déformation particulière de la gravité ont, en 7D, l’interprétation de variétés avec holonomies G2.Par contre, en réduisant la théorie de six à trois dimensions nous obtenons précisément la gravité 3D. Nous présentons aussi de nouvelles fonctionnelles pour les formes différentielles en six dimensions. Toutes sont invariantes sous difféomorphismes et deux d’entre elles sont topologiques. / In this thesis we take Einstein theory in dimension four seriously, and explore the special aspects of gravity in this number of dimension.Among the many surprising features in dimension four, one of them is the possibility of `Chiral formulations of gravity' - they are surprising as they typically do not rely on a metric. Another is the existence of the Twistor correspondence. The Chiral and Twistor formulations might seems different in nature. In the first part of this thesis we demonstrate that they are in fact closely related. In particular we give a new proof for Penrose's `non-linear graviton theorem' that relies on the geometry of SU(2)-connections only (rather than on metric).In the second part of this thesis we describe partial results towards encoding the full GR in the total space of some fibre bundle over space-time. We indeed show that gravity theory in three and four dimensions can be related to theories of a completely different nature in six and seven dimension respectively. This theories, first advertised by Hitchin, are diffeomorphism invariant theories of differential three-forms.Starting with seven dimensions, we are only partially succesfull: the resulting theory is some deformed version of gravity. We however found that solutions to a particular gravity theory in four dimension have a seven dimensional interpretation as G2 holonomy manifold. On the other hand by going from six to three dimension we do recover three dimensional gravity. As a bonus, we describe new diffeomorphism invariant functionnals for differential forms in six dimension and prove that two of them are topological.