Examensarbeten för masterexamen // Master Theses
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- PostEvaluate and develop high-performance GPS navigation using free GPS software(2015) Videkull, Ronny; Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap; Chalmers University of Technology / Department of Earth and Space SciencesSynthetic Aperture Radar (SAR) mounted on an aircraft allows us to create images of landscapes. In order to obtain such high resolution images it is crucial to accurately determine the flight-path of the instrument's platform. For centimeter-level accurate positioning of the aircraft, a differential positioning technique based on Global Navigation Satellite Systems (GNSS) is used. This method, also known as Real-Time Kinematic (RTK) positioning, utilizes carrier phase signals and relies on a second (fixed) "base station" with well known coordinates. In this thesis the accuracy of the open-source GNSS library RTKLIB was evaluated. A comparison with results from a commercial software has shown that RTKLIB is able to provide similar positioning performance. In general it could be concluded that the accuracy of RTKLIB is sufficient for the given SAR application. Moreover, a batch-driven processing chain utilizing RTKLIB was realized in order to minimize manual interactions. The thesis was conducted at Saab AB.
- PostFighting beam instabilities at CTF3(2011) Persson, Tobias; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentCTF3 is a test facility built to test key concepts of CLIC, which is a proposed Multi-TeV e+e collider. The success of CTF3 is crucial to demonstrate the feasibility of CLIC. This thesis focuses on beam stability and operational improvements at CTF3. It describes a software which I have developed for the operation of CTF3 and presents the results obtained. The main purpose of the software is to identify changes in the beam and trace their causes. The program has already become one of the most heavily used operational tools. Using the program I have also performed beam stability measurements in CTF3 and the results are compared with the requirements for CLIC. The results show that the CLIC requirements for the beam stability are fulfilled in the first part of CTF3. The causes of the beam instabilities have been determined and are explained. Tune measurements of the combiner ring at CTF3 are presented and compared to the model. The strong damping of the oscillation which was observed is explained.
- PostFinding meta stable states in proteins Identification of meta stable states in VPAL-peptide's dynamics(2012) Ruzhytska, Svitlana; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentProteins are very large biological molecules, responsible for many functions in living cells and organisms. Ever since they were recognized as a distinct class in 1789 by Antoine Fourcroy and others, proteins were, and still are due to their vital importance and high complexity, subject of studies of scientists from various fields of science all over the world. It was discovered, that each protein consists of one or more chains of amino acids compactly folded in space. This fully folded structure protein attain from the initial unfolded structure through intermediate ones. Moreover, scientists believe that protein properties and functions strongly depend on these structures. Fully folded structure, called native state, is the most preferable, due to the lowest overall free energy, so once it is reached, it holds for a long time, which increases chances for success in the experimental research of it (using, for example, X-ray crystallography or Nuclear Magnetic Resonance techniques). Unfortunately, this is not the case for intermediate structures, due to the either too fast (hard to record and notice) or too slow (hard to separate) folding process. That is when united physical, mathematical, and computer research dominates. This master thesis work presents a mathematical approach for studying intermediate protein structures. These intermediate structures, usually called meta stable states, are usable in multiple fields of research. For example, biochemistry and pharmaceutics are using them to optimize the shape of the drug molecules for achieving the best possible binding properties with respect to the target molecules; In biophysics it helps to find the folding pathways in the potential energy landscape; and in computational biology to reduce the amount of data needed to be stored obtained from the molecular dynamics simulations and also so that the problem can be partitioned into smaller pieces and be run in parallel on multiple computers. The goal of this work was to establish, if it is possible to apply spectral method for finding meta stable states of proteins. This was achieved through 3 major steps. First step was to obtain data for analysis, namely to perform molecular dynamics simulations resulting in the protein dynamics trajectory. Second step was to prepare this data for the analysis, namely to divide conformational trajectory into microstates and construct transition probability matrix. And, finally, the third step was to analyze data, by applying spectral method, which resulted in meta stable states. Tests were performed on the small peptide (peptide is the name for protein with the length of the chain less than 100 amino acids) consisting of only 4 amino acids named Valine-Proline-Alanine-Liucine (VPAL) [32]. This peptide, despite of its small size, attains properties of a protein, i.e. (folds through / has) meta stable states, however, because of its size, it makes it possible to get results comparatively quickly. Results obtained for VPAL-peptide were confirmed by those known in literature, which let us to conclude that it is possible to apply spectral method for finding meta stable states.
- PostFinding Predictive Patterns in Historical Stock Data Using Self-Organizing Maps and Particle Swarm Optimization(2012) Salomonsson, Hans; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThe purpose of this thesis is to find a new methodology for finding predictive patterns in candlestick charts without any predefining of how these might look. An algorithm combining particle swarm optimization and self-organizing map has been implemented and evaluated. Non-transformed daily open, high, low and close data has been used as input. The algorithm found predictive patterns that statistically significant outperformed random trading. Moreover, interesting properties such as the optimal length of the pattern, target length and similarity of input to found pattern are discussed.
- PostFrequency Sweeping Directivity of Bursting Alfv´en Waves on MAST(2012) Håkansson, Frida; Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap; Chalmers University of Technology / Department of Earth and Space SciencesIn a burning plasma, such as the next generation tokamak experiment ITER, significant numbers of highly energetic alpha particles will be produced. The presence of energetic particles may excite kinetic instabilities and affect the transport and heating of particles in the plasma. Of particular interest is the so called toroidal Alfv´en eigenmode (TAE) which can be excited by the super Alfv´enic alpha particles through resonant wave-particle interaction. In this thesis we identfy the linear TAEs with corresponding bursting nonlinear evolution in a discharge on the spherical tokamak MAST using the equilibrium code HELENA and the linear codes CSCAS and MISHKA. If this mode is excited there is a consecutive exponential growth of the linearized perturbations when the linear growth rate due to the fast particles is slightly larger then the total damping in the plasma. Nonlinear theory is then needed to describe the evolving nonlinear modes, which are observed to sweep in frequency with a preferred frequency sweeping directivity that changes in time. We investigate a possible reason for the change in preferred frequency sweeping directivity and derive an expression for the radial motion of the mode during the frequency sweeping.
- PostGPS Based Flight Motion Capture(2016) Arvidsson, Jonathan; Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap; Chalmers University of Technology / Department of Earth and Space SciencesThe objective of this study is to analyse Global Navigation Satellite System (GNSS) processing performance, to determine if it is possible, to capture the shape of a flight path of an airborne Synthetic Aperture Radar (SAR) radar, with a precision of less than 5 cm during the time it takes to record a SAR image, a SAR-run, without relying on a local reference receiver. The precision of position is achieved with the GNSS processing method Precise Point Positioning (PPP) which uses satellite information corrections and an extended Kalman filter. The data analysed were GPS observations from test flights with the Carabas 3 SAR helicopter including 12 flights with a total of 182 SAR-runs approximately 1 minute in length. The PPP processing was made by the position processing program RTKLIB. The PPP solution was compared with a Real Time Kinematics (RTK) solution. The average precision was 3.5 cm during a SAR-run. PPP is a precise technique with potential of capturing the flight movements. The implementation of a platform model and of Carrier Phase Ambiguity Resolution (CPAR) is expected to improve the performance.
- PostMagnetic separation of oxygen carriers from bed ash in heat and power plants(2019) Karlsson, Frida; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Mattisson, Tobias; Moldenhauer, PatrickIn response to climate change, research is currently conducted on the possibility of reducing the CO2 emissions from combustion plants. Technologies utilizing uidized beds can be used for combustion with low emissions. Chemical-looping combustion (CLC) and oxygen carrier aided combustion (OCAC) are two such technologies, using uidized beds with an oxygen-carrying bed material, which can be used instead of sand to transport oxygen between air and fuel. To minimize resource use and costs, it is important to reuse spent oxygen carriers. The possibility of recycling and reusing these oxygen carriers is studied in this work by separating the metal-based oxygen carriers from fuel ash through magnetic separation, and is based on the results of a previous Bachelor thesis project conducted in 2018. In this thesis, the magnetic properties of three oxygen carrier materials, ilmenite, LS Slag and Sibelco Calcined, that have been used in combustion processes are investigated using di erent characterization techniques. This is done in order to obtain a better understanding of the mechanisms which govern the magnetic behavior of oxygen carrier materials. Of the investigated materials, ilmenite and LD Slag are iron-based and Sibelco Calcined is manganese-based. Correlations between data from magnetic separation of these materials obtained in the Bachelor thesis and data obtained in this project are investigated. Di erent experimental techniques were employed, including measurements of magnetic susceptibility, X-ray powder di raction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The possibility to create a model by which the magnetic fraction can be predicted is further explored. The results indicate that there is some correlation between magnetic susceptibility and the obtained magnetic fraction, though not to the extent that would be needed in order to create a model. The results further suggest that the iron-oxide magnetite (Fe3O4), common in the iron-based oxygen carriers, is signi cant to the magnetic separability of these oxygen carrier materials. An oxygen carrier based on manganese ores could still be separated through magnetism, although this will likely depend upon the amount of iron in the sample. Suggestions can be made to use manganese ores with high concentrations of iron, as this is indicated to increase the magnetic properties of the material.
- PostModelling and Simulation of Tropospheric Water Vapour With Gaussian Random Fields-Time dependence beyond the frozen flow hypothesis(2018) Gingsjö, Henrik; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentOne of the major sources of error in Very Long Baseline Interferometry (VLBI) is signal delay due to tropospheric water vapour. Turbulent convection makes it inherently unpredictable and it must therefore be measured directly or modelled stochastically. In particular, realizations of delay signals are necessary to simulate the performance of existing and future VLBI networks which, in turn, is needed to optimize them and reduce errors. In previous work, modelling of tropospheric delay has been performed only on the spatial structure of refractivity through phenomenological second order statistics derived from Kolmogorov theory. Time dependence has been introduced exclusively through the frozen-flow hyporthesis. In this thesis, refractivity fields are modelled as Gaussian random fields. Efficient software is implemented to generate realizations of such fields sampled on a 3D grid. To achieve realistic time evolution of such gridded fields, it turns out to be both necessary and natural to introduce intrinsic time dependence beyond the frozen-flow hypothesis. Such time dependence can easily be made compatible with the temporal structure of Kolmogorov turbulence. The novel contributions of this thesis are methods of obtaining two kinds of time dependence for refractivity fields beyond the frozen-flow hypothesis. Firstly: Intrinsic time dependence compatible with Kolmogorov theory. Secondly: Translation by horizontal wind with arbitrary height and time dependence. The latter may provide a more realistic description of the planetary boundary layer which has strong wind shear and contains about 15% of the total water vapour; corresponding to delays of several centimetres.
- PostModelling heat and electricity supply in multifamily buildings with energy storage and solar PVs(2015) Borg, Filippa; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThe purpose of this thesis is to investigate how buildings with solar PVs and heat and electricity storage can be operated. The building considered has both a district heating connection and heat pumps, and can buy district heating and electricity on spot price. A model has been created to optimise the energy supply in the building by minimising the running cost utilising the energy storage, the price fluctuations and the produced solar electricity. The conclusion is that the combination of electrical and thermal storage works well, both are useful and contributes to the cost reduction. The running cost can be reduced with 24% with a thermal storage capacity of 1 000 kWhth and an electrical storage of 300 kWhel. The storage capacities reduces the dependencies from the electricity grid and the district heating network. With an electrical storage of 300 kWhel, the building can be self-sufficient on electricity 57% of the hours of the year, while without any storage only 29 %. The decrease in running cost is largest when increasing the electrical storage, since a larger share of the produced PV electricity can be utilised in the building which saves not only the spot price of electricity, but also taxes and grid fees. Due to the large fluctuations in the marginal district heating cost, the share of heat supplied by district heating increases with increased thermal storage. The heat pumps and the district heating can efficiently collaborate. A combination of the two technologies, together with spot price on both electricity and district heating, reduces the running cost of the building regardless of storage size. Utilising energy storage in buildings, as in this thesis, will increase flexibility in the energy system in the building and reduce dependency on the surrounding energy grids.
- PostSidelobe blanking in the presence of noise-like interference(2018) Wahlgren, Stina; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentInterference suppression in antenna arrays is an important topic for target detection in radar systems. This thesis investigates the performance of two different algorithms for determining whether a detection lies in the sidelobe or mainlobe of an antenna in the presence of noise-like interference (NLI). Both algorithms are based on a combination of sidelobe blanking (SLB) and sidelobe cancellation (SLC). The first algorithm is a simple cascading of SLC and SLB, while the second algorithm is a modification of this where multiple guard channels are used. The performance is evaluated with Monte Carlo simulations, where the antenna is modelled as a linear phased-array antenna and interference and target signals are modelled as uncorrelated, single-frequency plane waves. The influence of covariance estimation error, number of NLI sources, placement of auxiliary antennas, signal-to-noise ratio (SNR) and jammer-to-noise ratio (JNR) on performance and suitable blanking threshold is investigated. It is shown that the second algorithm performs better than the first when the number of NLI sources are few relative to the number of auxiliary antennas, and reduces to the same performance as the first algorithm when this is not the case.
- PostThe gravitationally lensed blazar PKS 1830-211 seen by Alma- Determination of the time delay between the lensed images(2016) David, Mariana Alves; Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap; Chalmers University of Technology / Department of Earth and Space SciencesAbstract PKS1830−211 is a blazar lensed by a foreground galaxy. The alignment of these two objects causes the formation of two distinct compact images embedded in a pseudo- Einstein ring. In this master thesis, we use multi-epoch and multi-frequency data, collected by the Atacama Large Millimeter/submillimeter Array (ALMA) in 2012 and 2014, with the aim of determining the time delay between the two lensed images. These have been resolved in all observations and, by modelling the flux of the North- East image and the flux ratio of both images, the time delay was found to be (28 ± 3) days. This result can be used in future work to better constrain the lens model of the system constituted by the blazar and its foreground galaxy. Furthermore, the physics of the jet was studied by interpretation of the measurements and spectral indices which varied between both periods and were found to be (0.77 ± 0.03) and (0.35 ± 0.10) in 2012 and 2014 respectively.
- PostTrade-offs between Black Carbon and CO2(2011) Sterner, Erik; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentIn addition to the greenhouse gases that cause radiative forcing (RF), the global climate is alsoaffected by particles that absorb or reflect light. Black carbon aerosols (BC) are the most important anthropogenic aerosols that enhance global warming. However, the contribution to RF from BC is considerably more uncertain than the RF of the well-mixed greenhouse gases that are present in the international climate policy discussions. The atmospheric lifetime of BC is only a few days, which suggests that reductions in emissions of BC would give a fast climatic response although BC also has indirect effects when it is deposited. It changes the albedo of snow or ice when deposited on for example Himalayan glaciers. The magnitude of the RF from BC is considerable, central estimates of the current black carbon global average radiative forcing lie in the range 0.1-0.8 W/m2. For this reason and the sizeable costs of reducing CO2 emissions there is a policy interest in reducing BC emissions. However, comparing benefits of reducing BC to reducing CO2 is a difficult task since there are many different types of aspects to the trade-off. In this thesis a reduced complexity coupled carbon cycle climate model, constructed primarily for studying the climatic impact of BC and such possible trade-offs, is presented. The model, which is called Physical Prediction Model for Future Radiative forcing and Temperature (PPM-FRT), includes virtually all of the anthropogenic climate forcers and the subsequent global annual average temperature change. In order to find policy relevant questions to ask and experiments to conduct, a series of different rounds of experiments were conducted. The final set of experiments investigate the effect on CO2 emissions pathways compatible with a certain climate target of the timing of black carbon emissions reductions start as well as the rate of decline of these emissions. The aspects of the pathway studied are the cumulative CO2 emissions up to 2100 and the rate of CO2 emissions reductions from a certain peak year. The climate target used is defined as a maximal increase of the global average surface temperature to 2°C above the pre-industrial level, a target acknowled-ged in the Copenhagen Accord signed by 138 countries in January 2010. For mean values of climate sensitivity and BC RF we find that the difference between zero and rapid reductions of BC emissions (red. of 4% per year)corresponds to a difference of between 60 and 140 GtC emitted during the 21st century. The variation in this result depends on the level of coupling between reductions in black carbon and reductions in a frequently co-emitted cooling carbonaceous aerosol called organic carbon (OC). This difference of between 60 and 130 GtC corresponds to a delay of the start year of CO2 emissions reductions by a few years (for a given CO2 emissions decline rate of 2.3% per year), illustrating the tradeoff between BC emission pathways and maximum cumulative CO2 emissions. A few years delay of CO2 emissions reductions represents an opportunity for the world to start taking measures against the single most important driver of the climate change: use of fossil fuels (without carbon capture and storage) and unsustainable land use changes, the two main reasons behind our emissions of carbon dioxide.
- PostTurbulent transport in fusion plasmas(2015) Ryrbo, Ken; Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap; Chalmers University of Technology / Department of Earth and Space SciencesIn order to improve the confinement time for tokamak type fusion reactors the nature of turbulent transport in fusion plasmas needs to be better understood. In this thesis the transport predicted by an advanced uid model, called the Weiland model, will be investigated analytically to further the understanding of which factors contribute to both inward and outward transport in various circumstances. The analytical expressions are then used to investigate how the flux of particles and heat relate to the density and temperature gradients in the plasma.