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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Improvement of measuring accurary of magnetic fields in borehole drilling

Sparr, Henrik, Palm Ekspong, Anton, Lindblad, Alexander January 2019 (has links)
To increase measuring accuracy in magnetotellurgic measurements anelectrode can be lowered into a borehole to create constraints forthe inversion. For this method a long cable is need to connect tothe electrode. This creates a new type of problems with parasiticeffects when the cable is placed on a winch made of metal. Toaccount for this, the behavior of the cable while on the winchwas measured. It was considered to be a multilayered multi rowcoil with a resistance of 2,4Ohm. The inductance of the winch wasmeasured for different frequencies and with different amount ofcable on the winch. With this data the physical properties of amultilayered multi row coil was numerically fitted. To explain thefrequency dependency of the inductance two different models wherecreated. Model one described the frequency dependency as randomand fitted the physical properties of the multilayered multi rowcoil once for every frequency. The second model (cftool-model)described the frequency dependency of the coil as a power-functionand fitted this behavior numerically in MATLABs curvefittingtoolbox (cf-tool). Both models predicted an inductance which increased with more cable on the winch and with lowerfrequencies. The models fitted the measured data points well insome areas. But for the measurements made with 135m of cable ofthe winch both models fitted poorly with relative errors of up to43%. This can be because of a systematic error made in how thecable was wound on the winch. To help to improve furthermeasurements the error needed to be within 10% which it overallfails to be. It is uncertain if more data and a better model wouldallow the error to reach tolerable levels or if the dependency ofthe winding of the cable onto the winch is too large.
2

A geophysical study of the Mertainen area : Modelling and interpretation of primarily aeromagnetic data

Ström, Tobias January 2018 (has links)
Nautanen Deformation Zone, is a prominent deformation zone in the Malmfälten area, which is of importance to understand for mineral exploration purposes. In spite of diverse geophysical data being available in Malmfälten and the good correlation between airborne measurements and geological observations, the area has not been fully investigated in detail using the aforementioned available data. A geological feature in connection with the Mertainen magnetite-breccia apatite iron ore deposit has been studied. Methods include the study of geological maps, the study of analytic signals of magnetic and gravity data, data processing, potential field- and 3D modelling and the interpretation of aforementioned models. Based on the observed and modelled data a fold structure has been detected in connection with Mertainen, and several mineralizations are believed to be structurally related to this fold. Furthermore, a potential mineralization structurally related with the fold has been detected, though it is quite likely that it isn't economically viable. / Nautanen Deformation Zone, är en framträdande deformationszon i Malmfälten området, vilken är av betydelse att förstå för mineral prospekterings ändåmål. Trotts att det finns ett stort utbud av geofysiska data i Malmfälten och att det finns en god korrelation mellan de flyggeofysiska mätningarna och geologiska observationer, så har området inte undersökts fullständigt med den tillgängliga datan. En geologisk struktur i koppling till apatit järn malms fyndigheten Mertainen has studerats. Bland metoder ingår studie av geologiska kartor, studie av de analytiska signlar hos magnetiska och gravimetriska data, data processering, potential fält- och 3D modellering samt tolkningen av ovannämnda modeller. Baserat på den observerade samt modellerade datan har en veck strucktur upptäckts i koppling till Mertainen, och flertalet mineraliseringar tros vara strukturellt relaterade till detta veck. Dessutom har en potentiell mineralisering strukturellt relaterad till vecket upptäckts, dock är det väldigt troligt att den inte är ekonomiskt brytbar.
3

Tilt sensing with low-cost inertial measurement units (IMUs) : Sensor calibration, accuracy specifications and application range

Riedesel, Philipp January 2016 (has links)
Many surveying engineering applications require the knowledge of the orientation parameters of instruments. One can use inertial measurement units (IMUs) to determine that. IMUs are combinations of several inertial sensors and comprise at least an accelerometer and a gyroscope. Therefore, they can detect accelerations and angular rates in a three-dimensional space. As micro-electro-mechanical systems, the sensors are increasingly getting smaller and lighter, but without being reduced in their accuracy. The smaller size facilitates diverse placing of the sensors, which allows a variety of uses. Moreover, several low-cost IMUs have been devised since the development of single-board computers. The main objectives of this work are to determine tilts using a low-cost IMU, and the accuracy of the sensor. Furthermore, it studies general IMU applications in surveying engineering, and examines whether low-cost versions are applicable. To fulfil the objectives, the study was based on a selected low-cost IMU. Two programs were developed as part of this work. One was to control the sensor and the other, to calculate the tilts and analyse the data. The IMU was mounted in front of the objective of the total station and aligned in different reference orientations. All measurements were performed under controlled thermal conditions. Thereby, it was ensured that no falsifications could appear due to ambient temperature influences. As a first step, the sensor calibration process was completed. It helped determine the signal offset parameter and their time-dependent change. The calibration was done using two present methods, the six-position and the multi-position methods. The calibrated IMU helped determine the tilts. This was done in the case of the accelerometer via trigonometric functions, which allowed an absolute orientation statement. In contrast, the gyroscope provided relative orientation with the multiplication of the detected angular variance and the time that passed. After that, a target-actual comparison with the reference information of the total station helped determine the external accuracy of the tilt from the IMU. Moreover, multiple measurements could give a statement of the internal accuracy. Finally, the Kalman Filter was added to smooth out the sensor data and combine it in real-time. The calibration methods showed similar results, and it was striking that the sensors did not show the expected drifts. The reason could be related to a pre-calibration by the manufacturer. On the one hand, the used IMU showed differences in the total station alignments in the order of 0.798° for the accelerometer and up to 4.3° for the gyroscope with the calibrated data. On the other, the differences in repeated measurements were at 0.024° for the accelerometer and 0.5° for the gyroscope. It was figured out different possible applications of IMUs in surveying engineering. Among other things, these included orientation monitoring of sensor platforms or the determination of the external orientation of unmanned aerial systems. For these applications, the usability depends on the achievable accuracy. In the case of the IMU chosen in this study, the proven accuracy is too inaccurate for these applications. There is a need for further investigation because the use of another sensor type may rectify the insufficient accuracy problem. Moreover, to achieve better accuracies and to make it possible to use the IMU in different ambient temperatures, the temperature influence must be determined.
4

Design and construction of a mobile equipment for thermal response test in borehole heat exchangers

Kamarad, Anthony January 2012 (has links)
In 2010, the Ground Source Heat Pumps (GSHPs) market in the European Union went up over one million (1 014 436 units at the end of 2010 according to EUROBSERV’ER 2011). In 2011, it was estimated around 1.25 million according to Bayer et al. (2012). With more than 378 000 units installed in 2010, according to the Swedish heat pump association (SVEP), the Swedish GSHPs market was the first in the EU. As for the French GSHPs market, it was estimated to 151 938 units in service in 2010, which propelled France at the third rank in the EU. However, despite a relatively important number of GSHPs installed in the whole EU, since 2008 GSHP sales have shrank. Even Sweden which has been the most competitive country sees its GSHP sales decline in the first quarter of 2012 (EUROBSERV’ER 2011). This report is the achievement of my Master of Science Thesis project. It also represents the end of my studies at INSA Lyon in France and concludes my degree in Energetic and Environment Engineering. This report deals with the improvement of a heat injection apparatus which is available at KTH (Royal Institute of Technology). This equipment is better known as Thermal Response Test (TRT) apparatus. This kind of equipment improves Borehole Heat Exchangers (BHE) design in terms of size and cost benefits. This technology is generally used to design GSHP installations in both domestic and industrial purposes. It allows to determine really important thermal BHE parameters: the thermal conductivity of the ground and the borehole thermal resistance. The report covers a theoretical description of TRT experiments, the reasons and objectives of such a project, the apparatus design and its construction. The last part is dedicated to a first experimental laboratory results and some problems met during the project course.
5

Undifferenced GPS for Deformation Monitoring

Andersson, Johan Vium January 2006 (has links)
This thesis contains the development of a deformation monitoring software based on undifferenced GPS observations. Software like this can be used in alarm systems placed in areas where the earth is unstable. Systems like this can be used in areas where people are in risk of getting hurt, like in earthquake zones or in land slide areas, but they can also be useful when monitoring the movements in buildings, bridges and other artefacts. The main hypotheses that are tested are whether it is possible to detect deformations with undifferenced observations and if it is possible to reach the same accuracy in this mode as when working in a traditional mode where the observations are differenced. The development of a deformation monitoring software based on undifferenced GPS observations is presented. A complete mathematical model is given as well as implementation details. The software is developed in Matlab together with a GPS observation simulator. The simulator is mainly used for debugging purposes. The developed software is tested with both simulated and real observations. Results from tests with simulated observations show that it is possible to detect deformations in the order of a few millimetres with the software. Calculations with real observations give the same results. Further, the result from calculations in static mode indicates that the commercial software and the undifferenced software diverge a few millimetres, which probably depends on different implementations of the tropospheric corrections. In kinematic mode the standard deviation is about 1 millimetre larger in the undifferenced mode than in the double differenced mode. An initial test with different observation weighting procedures indicates that there is a lot of potential to improve the result by applying correct weights to the observations. This is one of the aims in the future work within this project. This thesis are sponsored by the Swedish Research Council for Enviroment, Agricultural Sciences and Spatial Planning, FORMAS within the framework “Monitoring of construction and detection of movements by GPS ref no. 2002-1257" / QC 20101108
6

Numerical modelling of fluid flow and particle transport in rough rock fracture during shear

Koyama, Tomofumi January 2005 (has links)
The effects of different shearing processes and sample sizes on the fluid flow anisotropy and its impact on particle transport process in rough rock fractures are significant factors that need to be considered in the performance and safety assessments of underground nuclear waste repositories. The subjects, however, have not been adequately investigated previously in either laboratory experiments or numerical modeling. This thesis addresses these problems using numerical modeling approaches. The modeling consists of two parts: 1) fluid flow simulations considering more complex but realistic flow boundary conditions during shear processes that cannot be realized readily in laboratory experiments, using digitalized fracture surfaces scanned in the laboratory, so that anisotropic fluid flow induced by shearing with channeling phenomenon can be directly simulated and quantified; 2) particle tracking simulations to demonstrate the impacts of such channeling effects on characteristic properties of particle transport. The numerical method chosen for the simulations is the Finite Element Method (FEM). Scale effects were considered in the simulations by using fracture surface samples of different sizes. The distributions of fracture aperture during shear were obtained by numerically generating relative translational and rotary movements between two digitalized surfaces of a rock fracture replica without considering normal loading. From the evolutions of the aperture distributions during the shearing processes, the evolutions of the transmissivity fields were determined by assuming the validity of the cubic law locally. A geostatistical approach was used to quantify the scale effects of the aperture and transmissivity fields. The fluid flow was simulated using different flow boundary conditions, corresponding to translational and rotary shear processes. Corresponding to translational shear (with a 1 mm shear displacement interval up to a maximum shear displacement of 20 mm), three different flow patterns, i.e., unidirectional (flow parallel with and perpendicular to the shear direction), bi-directional and radial, were taken into account. Corresponding to rotary shear (with a 0.5o shear angle interval up to 90o), only the radial flow pattern was considered. The particle transport was simulated using the Particle Tracking Method, with the particles motion following the fluid velocity fields during shear, as calculated by FEM. For the unidirectional particle transport, the breakthrough curves were analyzed by fitting to an analytical solution of 1-D advection-dispersion equation. The dispersivity, Péclet number and tracer velocity, as well as their evolutions during shear, were determined numerically. The results show that the fracture aperture increases anisotropically during translational shear, with a more pronounced increase in the direction perpendicular to the shear displacement, causing significant fluid flow channelling. A more significant increase of flow rate and decrease in travel time of the particles in the direction perpendicular to the shear direction is predicted. The particle travel time and characteristics are, correspondingly, much different when such effects caused by shear are included. This finding may have an important impact on the interpretation of the results of coupled hydro-mechanical and tracer experiments for measurements of hydraulic properties of rock fractures, because hydraulic properties are usually calculated from flow test results along the shear directions, with the effects of the significant anisotropic flow perpendicular to the shear direction ignored. The results also show that safety assessment of a nuclear repository, without considering the effects of stress/deformation of rocks on fluid flow and transport processes, may have significant risk potential. The results obtained from numerical simulations show that fluid flow through a single rough fracture changes with increasing sample size, indicating that representativehydro-mechanical properties of the fractures in the field can only be accurately determined using samples of representative sizes beyond their stationarity thresholds. / QC 20101207
7

Enhancing Geophysical Applications with Electrical Resistivity Tomography Inversion : Uncovering the mysteries that lies beneath us

Morian, Anton January 2023 (has links)
Geophysical methods have been widely used to investigate the subsurface in various ap-plications, such as mineral exploration, geotechnical and environmental studies. Among these methods, electrical resistivity tomography (ERT) has gained popularity due to its non-invasive and high-resolution capability in mapping subsurface resistivity variations. In this report, we provide an overview of the theoretical principles behind ERT and discuss its practical applications. We highlight the importance of inversion in ERT data processing and explain how different filtering methods and parameters can affect the results. Our investigation shows that running 2D and 3D inversion in a cloud service is more than feasible and that filtering can significantly reduce the error between the model and reality. We demonstrate that the error can be reduced to less than a 0.1 % in the tested dataset with careful parameter selection. Overall, our findings emphasize the potential of ERT as a powerful tool for subsurface characterization and shed light on its practical implementation for various geophysical applications. / Geofysiska metoder har använts flitigt för att utforska underjordiska strukturer inom olikaforskningsområden, såsom mineralutforskning, geotekniska studier och miljöstudier. Bland dessa metoder har elektrisk resistivitetstomografi (ERT) vunnit popularitet på grund av dess icke-invasiva natur och förmågan att kartlägga resistivitetsvariationer med hög noggrannhet. I detta arbete presenterar vi en översikt över de teorier bakom ERT och diskuterardess praktiska tillämpningar. Vi poängterar betydelsen av inversion vid bearbetningen av ERT-data och förklarar hur olika filtreringsmetoder och parametrar kan påverka resultatet. Vår undersökning visar att det är fullt genomförbart att utföra 2D- och 3D-inversion i en molntjänst och att filtrering kan signifikant minska felet mellan modellen och verkligheten. Vi demonstrerar att felet kan reduceras till mindre än 0,1 %. Sammantaget belyser våra fynd potentialen hos ERT som ett kraftfullt verktyg för karakterisering av underjorden och belyser dess praktiska implementering inom olika geofysiska områden.
8

Elastic properties of the Singö zone from a discrete approach / Elastiska egenskaper för Singözonen baserat på ett diskret tillvägagångssätt

Åkerlind, Amanda January 2019 (has links)
A rock mass is characterised by the properties of the intact rock and the fractures. Considering the impact of both constituents is of vital importance for assessing the behaviour of the rock mass. In particular in the case of complex or heterogeneous rock mass compositions. A discrete approach, by using the Discrete Fracture Network (DFN) methodology, enables for the consideration of these aspects.This master’s thesis concerns the evaluation of elastic properties of the Singö deformation zone. A discrete approach has been applied by three-dimensional discrete fracture network modelling, using previously evaluated DFN parameters. The elastic properties have then been obtained by analytical means by using the methodology developed by Davy et al. (2018).The results show that in comparison to earlier evaluations of the elastic properties of the Singö zone, the respective Young’s moduli and Poisson’s ratios obtained by this thesis may indicate a weaker material. However, this study differs from the earlier evaluation by more extensive DFN modelling and the application of a state of stress which is more representative of the surroundings of the zone in Forsmark. The analysis indicates that theadequate model size is slightly larger than the maximum studied DFN model size. A suggested future improvement would be a re-evaluation and updating of the DFN parameters. As a concluding remark, the methodology of Davy et al. (2018) may prove successful in the future for the application to deformation zones. / En bergmassa karakteriseras av egenskaperna hos det intakta berget och dess sprickor. Det är därmed av vikt att båda dessa beståndsdelar beaktas vid utvärdering av bergmassans beteende, speciellt vid komplexa eller heterogena bergartssammansättningar.Detta examensarbete syftar till att utvärdera deformationsegenskaper för den så kallade Singözonen. Ett diskret angreppsätt har tillämpats genom modellering av tredimensionella diskreta spricknätverk med hjälp av tidigare utvärderade DFN-parametrar. Deformationsegenskaperna har sedan utvärderats med hjälp av metodiken som presenteras i Davy et al. (2018).Jämfört med tidigare utvärderade deformationsegenskaper hos Singözonen så indikerar resultaten av denna masteruppsats en svagare bergmassa, med hänsyn till uppskattade värden på E-moduler och tvärkontraktionstal. Däremot skiljer sig modelleringsprocessen i detta arbete mot de som utförts i de tidigare studierna. Detta med hänsyn till omfattningen av DFN-modelleringen samt tillämpandet i detta arbete av en spänningsansats som är mer representativ för Forsmarksområdet. Vidare indikerar resultaten att den representativa modellvolymen är något större än den största modellvolym som tillämpats i detta arbete. Förslagsvis kan en utvärdering och eventuell uppdatering av de använda DFN-parametrarna utgöra en möjlig utveckling eller förbättring av det arbete som utförts i detta mastersarbete. Slutligen kan det konstateras att framtida tillämpningar av den metodik som tagits fram av Davy et al. (2018) verkar lämplig att applicera på deformationszoner.
9

Spatial-Temporal Patterns of Urban Growth in Shanghai, China: Monitoring, Analysis, and Simulation

Zhang, Qian January 2009 (has links)
Supporting huge population, megacities are definitely the hot spots of production, consumption, and waste generation. Without careful investment and planning, megacities will be overwhelmed by burgeoning negative impacts on the environment, natural resources, and human health, as well as a host of social and economic issues. The unprecedented combination of economic and population growth since the Reform and Open Policy has led China into transition from a largely rural society to a predominantly urban one. Chinese cities, without question, have not escaped the danger of the series of problems during the rapid progress of urbanization. Therefore, monitoring the spatial-temporal patterns of urban sprawl and their impact on the environment is of critical importance for urban planning and sustainable development, especially in developing Chinese cities such as Shanghai. To date, few studies have focused on the urban trajectories of Shanghai over the past 30 years from a remote sensing perspective. Most of the studies were concentrated on the technical issues of image processing and classification. Moreover, research on spatial metrics has focused on analyzing remote sensing classification results rather than on the use of interpreting, assessing, and verifying urban simulation results. Furthermore, many researches merely focused on baseline projection and very few studies took into consideration urban growth scenarios so far. As yet there have been no reported scenario simulations of future Shanghai growth with several land-use categories within urban areas. The overall objective of this research is to investigate the integration of remote sensing, spatial metrics, and spatial-temporal models in the monitoring, analysis, and simulation of urban growth in Shanghai, China. The specific objectives are to: 1). monitor urban dynamics over time with multi-sensor remote sensing images; 2). quantify spatial-temporal properties of urban growth and representing the urban morphological structures by means of spatial metrics; and 3). simulate the geographic extent, patterns, and detailed catalogs of urban growth under different scenarios using Markov-Cellular Automata (Markov-CA) model to support decision making for a more sustainable Shanghai. Through this study, the combined approach using remotely sensed data with change detection techniques, spatial metrics, and a scenarios-based simulation model proved to be effective to understand, represent, and predict the spatial-temporal dynamics of urban growth. In detail, the segmented-based hierarchy classification and visual interpretation were effective methods to extract urban and industrial land with high-resolution remotely sensed images. Direct change detection using variables derived from tasseled cap transformation was efficient for monitoring impervious surface sprawl. Spatial metrics is a quick and executable way to assessing the impact of urban sprawl on landscape dynamic. Markov-CA model is a useful tool to simulate the scenarios of future urban developments and therefore provides the policy options for sustainable urban planning. The research results of urban trajectories and impervious surface sprawl showed that Shanghai experienced high-speed urban sprawl and the rate of urban expansion, however, was not homogeneous spatially and temporally. The general annual urban expansion speed was 34.8 km2 per year; nevertheless, it reached 80.2 km2 per year recent six years from 2001 to 2007, while it touched the bottom speed around 14.3 km2 per year during 1979-1989. The expanded area in the Puxi region was 5.23 times of its original area while that of Pudong region was 19.94 times of its original area during 1979-2007. The research results of landscape analysis demonstrated that greenbelt becomes fractured while infrastructural and commercial area is more and more aggregated in the central Shanghai area, and satellite images such as SPOT Pan, XS and Landsat TM with 10-30 meter resolution are sufficient for the landscape dynamic research in central Shanghai area. The results of scenarios-based simulation indicated that built-up areas in Shanghai will increase significantly in 2025 and Shanghai will experience less urban sprawl and retain a better environment in 2025 under service-oriented center (SOC) than under baseline (NS) or manufacturing-dominant center (MDC) scenario. If favorable policy for MDC scenario is adopted, however, there will be a lot of manufacturing industries gathering in Shanghai and more agricultural lands will be encroached. The present research focused on the analysis of physical and morphological aspects of urban growth. Urban land-use dynamics are, however, intrinsically linked with socio-economic, political, or demographic drivers. Trying to fill in the missing link between traditional urban geography and urban remote sensing & urban simulation and to improve understanding of the interactions between human and natural aspects in the urban socio-ecosystem is the major focus in the next phase of the Ph.D. research. Keywords: Urban growth, Spatial-temporal pattern, Remote sensing, Spatial metrics, Scenarios-based simulation, Shanghai / QC 20110224
10

Physical properties of coarse particles in till coupled to bedrock composition based on new 3D image analysis method

Tafesse, Solomon January 2010 (has links)
The physical properties of the coarse fraction of the till (0.4 to 20 cm) and the surface boulders have been studied at two different sites in Sweden. The research work included: development of a new image analysis software for 3D size and shape measurements of particles; lithological analysis on multiple size fractions in till and magnetic susceptibility survey on coarse till clasts, surface boulders and local bedrock. The new 3D image analysis method provides an enormous amount of size and shape data for each particle in the coarse fraction (2 to 20 cm) in till. The method is suitable for field study, cost effective and the software is executable in Matlab. The field imaging method together with the image analysis software give non subjective results of size and shape of coarse particles and makes it feasible and easy to study representative sample size, which is one tonne for testing clasts of size up to 20 cm. The lithological analysis of the multiple size fraction of the till clasts has been investigated on six different size fractions of the till (0.4 to 20 cm); the result of the different samples from the two sites shows that this method can potentially be used as a stratigraphic tool in the areas where there is no unique indicator lithologies. The magnetic susceptibility has been made on the surface boulders, the 6-20 cm till fraction and on insitu bedrock outcrops near to the study sites. The method has good potential for determining stratigraphic relationships between different till units as well as for determining the provenance ofcoarse clasts and surface boulders. / QC 20110413

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