FEM analysis of ultra thin mirror supporting structure effect on surface deformation in gravity field

2006 ◽  
Author(s):  
Qitai Huang ◽  
Qiang Gao ◽  
Jingchi Yu
Keyword(s):  
Gravity Field ◽  
Surface Deformation ◽  
Fem Analysis ◽  
Structure Effect ◽  
Supporting Structure

Design of Supporting Structure for Plane Grating and Surface Deformation Calculation

2011 ◽  
Vol 40 (10) ◽  
pp. 1514-1520
Author(s):  
梁彪 LIANG Biao ◽  
刘伟 LIU Wei ◽  
陈程 CHEN Cheng
Keyword(s):  
Surface Deformation ◽  
Supporting Structure

The Effect of the Disturbing Potential for the Gravity Field

2015 ◽  
Vol 220-221 ◽  
pp. 257-263
Author(s):  
Petras Petroškevičius ◽  
Rosita Birvydiene ◽  
Darius Popovas
Keyword(s):  
Gravity Field ◽  
Surface Deformation ◽  
Equipotential Surface ◽  
Material Point ◽  
Gravity Potential ◽  
The Moon ◽  
Disturbing Potential ◽  
Normal Height ◽  
Earth’S Gravity Field ◽  
Accuracy Of Measurements

The Earth’s gravity field tends to change due to various reasons. These are diverse processes occurring inside the Earth or changes initiated by human activity. The increasing accuracy of measurements has enabled to take into consideration fluctuations in the gravity field. The article presents research study on the effect of gravity potential describing variations in the gravity field affecting gravity field elements related to the performed measurements. Due to the effect of the disturbing potential, a change in gravity and the deviation of vertical and equipotential surface deformation have been determined. The paper has analyzed the disturbing effect of the material point or homogeneous sphere and has specified the possibilities of assessing the disturbing effect of any form of the homogeneous body. Based on the tidal potential induced by the celestial body, the disturbing effect of the Moon and Sun onto the Earth’s gravity field has been assessed. The carried out research indicates that the range of deformation changes in the equipotential surface of the Earth’s gravity field induced by the effect of the Moon is equal to 0.4824 m, whereas that of the Sun makes 0.1861 m. The conducted studies prove that, due to the effect of the Moon, the direction of the vertical, in terms of the Earth’s surface, tends to change up to 0.0541", and as a result of the Sun’s effect it could reach 0.0204". Having assessed the Lunisolar effect in the first order vertical network measurements in Lithuania, in a polygon with the perimeter of 451 km, it has been determined that the closing error of normal height difference has decreased by the factor of 1.3.

scholarly journals Interannual variations of degree 2 from geodetic observations and surface processes

2020 ◽  
Author(s):  
S Rosat ◽  
N Gillet ◽  
J-P Boy ◽  
A Couhert ◽  
M Dumberry
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Surface Deformation ◽  
Global Scale ◽  
Surface Processes ◽  
Interannual Variations ◽  
Mass Redistribution ◽  
Continental Hydrology ◽  
Gravity Signal ◽  
Gps Time Series

Summary Geodetic observations from space continuously record surface deformation and global mass redistribution with an increasing accuracy. In parallel, surficial processes (oceanic, atmospheric, and hydrological loading) are more and more precisely modeled.We propose a confrontation of the geodetic Global Positioning System (GPS) and gravity-field satellite laser ranging (SLR) observations at decadal and interannual time scales, in terms of resolution, correlation and comparison with surficial loading models. We focus on the largest global scale signals of degree 2. At interannual periods, surface deformations retrieved from GPS time-series do not exceed 0.8 mm. Our analysis does not reveal the presence of a dominant signal at a specific period, except perhaps for a signal of approximately 3 yr likely connected to the loading response to El Nio / Southern Oscillations. Contrary to the results of previous studies, we do not find in GPS time-series a clear 6-yr oscillation associated with a degree-2 order-2 pattern. Interannual variations in the degree-2 Stokes coefficients of the gravity field do not exceed 2 × 10−11. We do not detect a dominant gravity signal at one specific period but instead a broad spectrum of frequencies. The comparison between the degree 2 deformations built from GPS time-series with a prediction from SLR derived gravity variations reveals some correlations, though their differences remain important. This highlights the present day limitations of these techniques in their ability to characterize global scale interannual variations. Hydrological loading models show some correlations with both GPS and SLR signals, but we cannot firmly establish that continental hydrology is dominantly responsible for the observed variations. Given the current limits in the resolution of both gravity and surface deformation and in the modelling of surface processes, we conclude that it will be a challenge to retrieve a geodetic signal of sub-decadal period originating in the Earth’s core.

scholarly journals Satellite monitoring of mass changes and ground subsidence in Sudan’s oil fields using GRACE and Sentinel-1 data

2020 ◽  
Author(s):  
Nureldin Gido ◽  
Hadi Amin ◽  
Mohammad Bagherbandi ◽  
Faramarz Nilfouroushan
Keyword(s):  
Gravity Field ◽  
Land Subsidence ◽  
Surface Deformation ◽  
Oil Fields ◽  
High Rate ◽  
Ground Subsidence ◽  
Satellite Monitoring ◽  
Oil Storage ◽  
The Earth ◽  
Sar Data

<p>Monitoring environmental hazards, due to natural and anthropogenic causes, is one of the important issues, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, e.g. the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this aspect. GRACE missions are dedicated to model the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects Synthetic Aperture Radar (SAR) data which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure, form compaction and consequently land subsidence occurs which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, i.e. Heglig, Bamboo, Neem, Diffra and Unity-area oil fields. Then we correlate the results with the available oil wells production data for the period of 2003-2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Due to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS change and extracted oil and water volumes. The trend of GWS changes due to water and oil depletion ranged from -18.5 to -6.2 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using Persistent Scatterer Interferometry (PSI) method shows high rate of subsidence i.e. -24.5, -23.8, -14.2 and -6 mm/year over Heglig, Neem, Diffra and Unity-area oil fields respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.</p>

scholarly journals Satellite Monitoring of Mass Changes and Ground Subsidence in Sudan’s Oil Fields Using GRACE and Sentinel-1 Data

2020 ◽  
Vol 12 (11) ◽  
pp. 1792 ◽  
Author(s):  
Nureldin A.A. Gido ◽  
Hadi Amin ◽  
Mohammad Bagherbandi ◽  
Faramarz Nilfouroushan
Keyword(s):  
Gravity Field ◽  
Land Subsidence ◽  
Large Scale ◽  
Surface Deformation ◽  
Oil Fields ◽  
High Rate ◽  
Ground Subsidence ◽  
Satellite Monitoring ◽  
Oil Storage ◽  
Sar Data

Monitoring environmental hazards, owing to natural and anthropogenic causes, is an important issue, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, for example, the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this respect. GRACE missions are dedicated to modeling the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects synthetic aperture radar (SAR) data, which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure and form compaction and, consequently, land subsidence occurs, which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, that is, Heglig, Bamboo, Neem, Diffra, and Unity-area oil fields. Then, we correlate the results with the available oil wells production data for the period of 2003–2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Owing to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS anomalies (ΔGWS) and extracted oil and water volumes. The trend of ΔGWS changes due to water and oil depletion ranged from –18.5 ± 6.3 to –6.2 ± 1.3 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using the persistent scatterer interferometry (PSI) method shows a high rate of subsidence, that is, –24.5 ± 0.85, –23.8 ± 0.96, –14.2 ± 0.85, and –6 ± 0.88 mm/year over Heglig, Neem, Diffra, and Unity-area oil fields, respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.

A Shelved Structure for the Support of An Electron Optical Column

1970 ◽  
Vol 28 ◽  
pp. 366-367
Author(s):  
P.H. McLaughlin
Keyword(s):  
Electron Source ◽  
Floating Platform ◽  
Supporting Structure

A shelved structure for the support of an electron optical column affords advantages both to the designer and the user. A lens may be removed for cleaning for example, without demounting the remaining lenses. A custom device for another example, may be placed on a shelf, substituting for the standard lens perhaps so that some specialized research may be undertaken. Especially advantageous is a shelved arrangement if the column assembly is designed to hang from a supporting structure such as a gas borne floating platform, as is the case with the system described below.As shown on the schematic, a floating platform (I) supports the electron source apparatus (2) and a U-shaped column support shelf (3). The column support shelf acts as a key for locating and supporting three struts (4) which with nuts (5) support the condenser shelf (6), the objective shelf (7), the upper projector shelf (8), and the lower projector shelf (9).

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