This Master's Thesis deals with geometric modeling methods and theirs implementation in Octave (Matlab), which is ideal for the practical realization. The first part of the thesis is focused on a very simplified image source method, which is able to calculate and render the 2D impulse response of rectangular rooms. The next part is aimed on~the same method, but extended by three-dimensional simulation of polyhedral prism-shaped rooms. There is both an explanation of theoretical and mathematical aspects and a~documentation of the implemented source code. Extended image source method is able to generate sound representation of impulse response characteristics, and use it for auralization, which is achieved by using convolution of both the input sound source and the calculated impulse response. At the end there are two practical examples for both methods with explanatory illustrations.

This term project addresses the construction of kD tree acceleration structures and parallelization of this construction using GPU. At the beginning, there is an introduction of the reader into CUDA platform for parallel programming. There is a decription of generic principles as well as specific features that will be used in this thesis. Following that the reader is put into the issue of acceleration structures for Ray tracing. These structures are described and the kD tree acceleration structure and its variants are portrayed in detail. After that the analysis of chosen kD tree variant is broken down and the problems and issuse of its parallel implementation are adressed. As a part of implementation discription, there is a short descripton of CPU variant and detailed specifications of the CUDA kernels. The testing section brings the results of implementation in form of CPU vs GPU comparison, as well as evaluation of how much the metric set in design was fulfilled. In the end there is a summary of achieved goals and results followed by possible future improvements for the implementation.

Le but de ce travail est l'étude de la connectivité anatomique et fonctionnelle desréseaux neuronaux et le développement des nouveaux outils à cet effet. Car le dernieraspect est une préoccupation majeure de la neuroscience actuelle, nous avonsdeveloppé d'abord un nouveau traceur virale permettant la reconstruction neuronale.Nous avons ensuite appliqué cet et d'autres techniques pour sonder les défauts deconnectivité neuronale dans le syndrome de l'X fragile.Dans la première partie, nous avons discuté les avantages et inconvénients d'unetechnique émergente en utilisant un nouveau type de vecteur viral qui permet uneunique application pour l’étude du cerveau.Dans la deuxième partie, nous avons développé, au départ de ce vecteur viral, unenouvelle variante de faciliter le traçage et reconstruction des caractéristiquesmorphologiques de neurones. Nous avons montré la force de cette varianteantérograde du virus de la rage recombinant glycoprotéine supprimé pour lareconstruction de calcul de toutes les caractéristiques morphologiques clés deneurones: les dendrites, épines, les axones longs envergure dans tous les terminaux ducerveau et les boutons.Dans la troisième partie, nous avons examiné les modifications dans la connectivitédes structures cérébrales dans le syndrome du X fragile (FXS). FXS est le retardmental héréditaire la plus fréquente et la forme génétique la plus fréquente del'autisme, ce qui conduit à l'apprentissage et de la mémoire des déficits, lescomportements répétitifs, des convulsions et une hypersensibilité à des stimulisensoriels (visuels). Une des hypothèses éminents dans le domaine de l'autismesuppose une phénotype de hyper-connectivité locale mais de hypo-connectivité pourles connexions longue portée. Pour tester cette hypothèse dans un modèle de sourisFXS nous avons utilisé l'imagerie par résonance magnétique, pour balayer la totalitédu cerveau et de mesurer la connectivité anatomique et fonctionnel. Cela nous apermis d'identifier des altérations de connectivité dans plusieurs domains. Après nous8avons utilisé des traceurs viraux pour explorer un de ceux domains plus detaillé. Enutilisant le virus de la rage rétrograde à quantifier le nombre de neurones projetantvers ces zones, nous avons confirmé une connectivité d'entrée modifié pour le cortexvisuel primaire, ce qui pourrait contribuer au traitement visuel altéré de l'information.Nous avons découvert une connectivité réduite à longue portée globale anatomique etfonctionnelle entre plusieurs régions du cerveau, l'identification FXS comme unepathologie de la connectivité neuronale, ce qui pourrait expliquer les difficultés deplusieurs stratégies de sauvetage visant des cibles moléculaires sont actuellementconfrontés. / The goal of this work was the investigation of the anatomical and functionalconnectivity of neuronal networks and the development of novel tools for thispurpose. Since the latter aspect is a major focus of current neuroscience, we firstsought a novel viral tracer enabling sparse neuronal reconstruction and neuronclassification. We then applied this and other techniques to probe neuronalconnectivity defects in Fragile X Syndrome.In the first part we discussed the merits and drawbacks of a emergingtechnique using a new type of viral vector that allows in a unique manner mapping ofthe input of a given brain area.In the second part we developed, departing from this viral vector, a newvariant to facilitate the tracing and reconstructing of morphologic features of neurons.We showed the strength of this anterograde variant of the recombinant glycoproteindeletedrabies virus for computational reconstruction of all key morphologicalfeatures of neurons: dendrites, spines, long-ranging axons throughout the brain andbouton terminals.In the third part we examined alterations in the wiring of brain structures inthe Fragile X Syndrome (FXS). FXS is the most common inherited mental retardationand most frequent genetic form of autism, leading to learning and memory deficits,repetitive behavior, seizures and hypersensitivity to sensory (e.g. visual) stimuli. Oneof the eminent hypotheses in the autism field assumes a local hyper- connectivityphenotype but hypo-connectivity for long-ranging connections. To test this hypothesisin a FXS mouse model we used magnetic resonance imaging, to scan the entire brainand measure the anatomical and functional connectivity. This allowed us to identifyconnectivity alterations in several areas that we further explored using viral tracers.Using retrograde rabies virus to count the number of neurons projecting to such areaswe confirmed an altered input connectivity to the primary visual cortex, which couldcontribute to the altered visual information processing. We discovered an overallreduced anatomical and functional long-range connectivity between several brainareas, identifying FXS as pathology of neuronal connectivity, which might explain thedifficulties several rescue strategies aiming at molecular targets are currently facing.

The Transatlantic Trade Investment Partnership (TTIP) was a large trade deal that was negotiated between EU and the US under the years of 2013 and 2019. The negotiations for TTIP started with big expectations for both actors but ended without any succeeded agreement. The purpose of this study is therefore to investigate how this trade deal ended in failure despite the big commitment from these two negotiators.  To achieve this purpose, the study was designed accordingly to the theory of Two-level games. A theory that claims that international agreements depends on the domestic political situation. Focus was for that reason put on identifying changes in the political situation in EU and the US.  The method process tracing was then introduced to help identify these kinds of changes. Based on this method, the study found three possible changes that could have stopped the talks of TTIP: The opposition in EU, Brexit, and Donald Trump. To conclude how these three transformations affected the negotiations, evidence describing these three events was collected and thence tested in different process tracing tests. The results of the process tracing tests found that both Brexit and Trump had affected the talks negatively. Moreover, was the study also able to conclude that trade policy of Donald Trump was the factor that lastly ended the negations of TTIP.

How can we explain the paradoxical outcomes of resource efficiency? As a key pillar of worldwide sustainable development policies, the concept of resource efficiency has become increasingly important to scrutinize. The overreliance on efficiency coupled with the intention of conserving scarce resources can sometimes backfire. Understanding the intermediate process that leads to the negative, paradoxical outcome is imperative for a sustainable future, especially for societies that risks resource degradation. This study takes the explanatory route and aims to problematize the usage of efficient technology in a resource scarce developing country, namely, Morocco. It is argued that the causal mechanism which links the independent variable (drip irrigation technology) to the observed outcome (total increased resource consumption) has to do with production and consumption processes, which is theorized to be spurred by efficiency. These mechanisms have been derived from the theory of Jevons Paradox and juxtaposed with empirical findings from the Guerdane irrigation scheme, a scheme which sought to increase productivity and simultaneously reduce water scarcity. The study makes use of the case-study approach and the process-tracing method. The chosen method provides a means for establishing a timeline of events, alternative explanations, as well as providing grounds for a primary explanation for the observed outcome. The findings point to reduced labour costs and initial water savings as the empirically derived causal mechanisms. These mechanisms, spurred by the implementation of drip irrigation technology, consequently gave rise to the expansion of irrigated land which in turn increased water withdrawals and eventually resulted in a paradoxical, negative outcome where the total consumption of water resources increased. Taken together, these results deepen our understanding of the problematic usage of efficient technology when different types of social processes are not accounted for.

Solar energy is one of a very few low-carbon energy technologies with the enormous potential to grow to a large scale. Currently, solar power is generated via the photovoltaic (PV) and concentrating solar power (CSP) technologies. The ability of CSPs to scale up renewable energy at the utility level, as well as to store energy for electrical power generation even under circumstances when the sun is not available (after sunset or on a cloudy day), makes this technology an attractive option for sustainable clean energy. The levelised electricity cost (LEC) of CSP with thermal storage was about 0.16-0.196 Euro/kWh in 2013 (Kost et al., 2013). However, lowering LEC and harvesting more solar energy from CSPs in future motivate researchers to work harder towards the optimisation of such plants. The situation tempts people and governments to invest more in this ultimate clean source of energy while shifting the energy consumption statistics of their societies from fossil fuels to solar energy. Usually, researchers just concentrate on the optimisation of technical aspects of CSP plants (thermal and/or optical optimisation). However, the technical optimisation of a plant while disregarding economic goals cannot produce a fruitful design and in some cases may lead to an increase in the expenses of the plant, which could result in an increase in the generated electrical power price. The study focused on a comprehensive optimisation of one of the main CSP technology types, the linear Fresnel collector (LFC). In the study, the entire LFC solar domain was considered in an optimisation process to maximise the harvested solar heat flux throughout an imaginary summer day (optical goal), and to minimise cavity receiver heat losses (thermal goal) as well as minimising the manufacturing cost of the plant (economic goal). To illustrate the optimisation process, an LFC was considered with 12 design parameters influencing three objectives, and a unique combination of the parameters was found, which optimised the performance. In this regard, different engineering tools and approaches were introduced in the study, e.g., for the calculation of thermal goals, Computational Fluid Dynamics (CFD) and view area approaches were suggested, and for tackling optical goals, CFD and Monte-Carlo based ray-tracing approaches were introduced. The applicability of the introduced methods for the optimisation process was discussed through case study simulations. The study showed that for the intensive optimisation process of an LFC plant, using the Monte Carlo-based ray-tracing as high fidelity approach for the optical optimisation objective, and view area as a low fidelity approach for the thermal optimisation objective, made more sense due to the saving in computational cost without sacrificing accuracy, in comparison with other combinations of the suggested approaches. The study approaches can be developed for the optimisation of other CSP technologies after some modification and manipulation. The techniques provide alternative options for future researchers to choose the best approach in tackling the optimisation of a CSP plant regarding the nature of optimisation, computational cost and accuracy of the process. / Thesis (PhD)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

Concern over the altering climate due to the release of anthropogenic greenhouse gases has caused a major shift in the developments of ways to minimise human impact on the climate. Solar energy is seen as one of the most promising sources to transform the energy market for low-carbon energy generation. Currently, solar power is generated via photovoltaic (PV) and concentrating solar power (CSP) technologies. The advantage of CSPs to scale up renewable energy to utility level, as well as to store thermal energy for electrical power generation when the sun is not available (after sunset or during cloudy periods) makes this technology an attractive option for sustainable clean energy. CSP development, however, is still in its infancy, and for it to be a competitive form of energy-generation technology, techno-economic developments in this field need to improve the efficiency and decrease the costs of this technology. A policy report by the European Academies’ Science Advisory Council (EASAC) (2011) indicated that central receiver (solar tower) CSP systems show the greatest margin for technological improvements (40% to 65% is estimated), and that an improvement in receiver technology could make the greatest contribution to increase efficiency. This study therefore focused on analysing the optical and thermal performance of a new proposed solar cavity molten salt receiver design for a central receiver CSP system using a numerical approach. In this study, the receiver’s performance was analysed by first selecting an existing heliostat field, Planta Solar 10 (PS-10). For the numerical analysis to reflect conditions that are as realistic as possible, numerical models for different aspects were selected and validated. For modelling the sun, the solar tracking numerical model proposed by Iqbal (1983) was selected and implemented after literature and comparison showed adequate results. The direct normal irradiation (DNI) was modelled by applying a clear sky model, with the parameterisation model C proposed by Iqbal (1983) as the chosen model. The variables in this model that were subject to temperature, and humidity values were more accurately presented by adding numerical approximations of the region’s actual weather data. The DNI model reflected realistic fluctuations. For the thermal modelling, a validation study was conducted on impingement flow heat transfer to select an appropriate Reynolds-averaged Navier-Stokes (RANS) model that would provide accurate results when conducting the thermal performance test on the receiver. The study concluded that the transitional Shear Stress Transport (SST) turbulence model performed the best. A new method was also developed and validated that allows one to not only simulate complex geometries within the Monte Carlo ray tracing environment SolTrace, but also to apply the results obtained by simulating this model as a heat source within the computational fluid dynamics (CFD) environment ANSYS Fluent. This allows SolTrace modelling to be more accurate, since models do not need to be approximated to simple geometries. It also provides an alternative for solar modelling in ANSYS Fluent. The optical analysis was conducted by first performing an analysis on the receiver aperture and studying its sensitivity on the captured flux. This was followed by analysing the optics of the proposed receiver, the flux distributions on a simplified absorber surface area, and how these distributions are altered by changing some parameters. An in-depth analysis was finally done on the absorber area by applying the aforementioned model to simulate complex geometries within SolTrace, with the results illustrating the difference of the detailed geometry on optical modelling. An alternative receiver design with improved optical features was proposed, with an initial study providing promising results. The thermal analysis was done within the CFD environment, with only a section of the absorber surface area considered, and by applying the solar flux simulated during the optical analysis as heat source within the geometry model. This allowed the model to simulate the effects of re-radiation at the surface of the absorber while simulating the heat transfer at the fluid molten salt side simultaneously. The results showed that, for the current design and requirements, the absorber surface temperature reaches impractical temperatures. Altering the design or being more lenient on the requirements has, however, shown dramatic improvements in terms of thermal performance. Sensitivity studies for both the optical and thermal analyses have shown that changes in design can dramatically improve the performance of the design, making it a possible feasible receiver design for central receiver systems. / Dissertation (MEng)--University of Pretoria, 2019. / National Research Foundation (NRF) / Mechanical and Aeronautical Engineering / MEng / Unrestricted

The educational industry has evolved with the development of computer technology. The online education system (OES) provides a more effective and efficient educational strategy for students benefiting from computer science technologies. There is a need for a mapping of knowledge definition from the traditional education system to the data gathered from the non-traditional OES. This would make the measurement of knowledge possible for OES. The study aims to (a) find an appropriate knowledge definition through a literature review process, and (b) based on the definition measure students’ knowledge in OES, such as Hypocampus, by using machine learning techniques. Experiments were conducted using a well-known Bayesian KnowledgeTracing (BKT) model. The evaluation was performed on 3300 students studying medicine in France using Hypocampus OES. As a result, the student’s knowledge was measured in skills, performance, and achievement per subject with 81% average accuracy. The obtained results suggest the potential of the presented approach for measuring students’ knowledge in OES.

The Grand Ethiopian Renaissance Dam built on the Nile has sparked conflicts for over twelve years now since it was first announced in 2009. But in 2020 when Ethiopia finally started to fill this behemoth of a dam hostilities ramped up between Egypt and Ethiopia. Because around 95% of Egypt's freshwater comes from the Nile and this dam is positioned upstreams of Egypt's vital water source. As such, Egypt did not take lightly to Ethiopia's challenge towards their historical water hegemony and responded with threats of violence and war. To further complicate this situation Egyp is facing an acute water shortage in 2025 and climate change will throw a wrench into the whole situation as droughts and floods will become more frequent as the world grows warmer. The empirical work of this thesis used a process-tracing approach to identify that realistic fears are driving Egypt to react with aggression and seek conflicts. However, Egypt's goal is to achieve cooperation and create a water-sharing agreement with Ethiopia. The problem is that Ethiopia does not want to give up their dam control and is satisfied with the status quo, while Egypt is striving to create a situation where they both have something to gain from cooperation. Be it through threatening to invade Ethiopia and blow the dam up or through their use of international institutions to force Ethiopia into cooperation. In the end, the conflict continues as no cooperation agreement has been signed.

A key aspect of immersive audio is realistic acoustics. To get plausible acoustics for an environment the impulse response can be generated using acoustic simulations and should ideally be updated in real-time for interactive applications. In this thesis the listening experience of sound generated with an interactive sound propagation engine was explored and compared to spatial sound produced with a static impulse response. The aim was to evaluate the sound experience for applications outside of virtual reality, with computational cost in consideration. This was done by conducting a user study where the participants got to interact and compare the two sound methods in different environments. The study was performed using a custom developed application integrated with a pre-existing sound propagation engine. The results from the user study showed no obvious perceptive difference between the two sound rendering methods that could justify the extra computations. Overall there was even a slight preference for the stereo method that used a static impulse response. However, there were qualities to both sound rendering methods that were preferred depending on the environment. Another thing that was investigated in the work of this thesis was how the varying accuracy of localization of sound in different directions can be used in acoustic ray tracing algorithms. An alternative sampling method was developed that uses a biased distribution based on spatial resolution of human hearing instead of traditional uniform sampling. The computation time of the random sampling phase increases, but could potentially reduce the number of ray samples needed. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>