Computational Fluid Dynamics Coupled to Discrete Element Method (CFD-DEM) is widely used in simulating a large variety of particulate flow system. This Eulerian-Lagrangian technique tracks all the particles included in the system by the application of point mass models in their equation of motion. CFD-DEM is a more accurate (and more expensive) technique compared to an Eulerian-Eulerian representation. Compared to Particle Resolved Simulations (PRS), CFD-DEM is less expensive since it does not require resolving the flow around each particles and thus can be applied to larger scale systems. Nevertheless, simulating industrial and natural scale systems is a challenge for this numerical technique. This is because the cost of CFD-DEM is proportional to the number of particles in the system under consideration. Thus, massively parallel codes are used to tackle these problems with the help of supercomputers. In this thesis, the CFD-DEM capability in the in-house code Generalized Incompressible Direct and Large Eddy Simulation of Turbulence (GenIDLEST) is used to investigate large scale dense particulate flow systems. Central to the contributions made by this work are developments to reduce the computational cost of CFD-DEM. This includes the development and validation of reduced order history force model for use in large scale systems and validation of the representative particle model, which lumps multiple particles into one, thus reducing the number of particles that need to be tracked in the system. Numerical difficulties in the form of long integration times and instabilities encountered in fully coupling the fluid and particle phases in highly energetic systems are alleviated by proposing a partial coupling scheme which maintains the accuracy of full-coupling to a large extent but at a reduced computational cost. The proposed partial-coupling is found to have a better convergence behavior compared to the full coupling in large systems and can be used in cases where full coupling is not feasible or impractical to use. Alternative modeling approaches for the tangential treatment of the soft-sphere impact model to avoid storing individual impact deformation are proposed and tested. A time advancement technique is developed and proposed for use in dense particulate systems with a hard-sphere impact model. The new advancement technique allows for the use of larger time steps which can speed-up the time to solution by as much as an order of magnitude. / PHD

The behavior of the ballast particles during their interaction with tamping tines in tamping operation is studied by developing a simulation model using the Discrete Element Model (DEM), with the aim of optimizing the railroad tamping operation. A comprehensive literature review is presented showcasing the applicability of DEM techniques in modeling ballast behavior and its feasibility in studying the fundamental mechanisms that influence the outcome of railroad tamping process is analyzed. The analysis shows that DEM is an excellent tool to study tamping operation as its important and unprecedented insights into the process, help not only to optimize the current tamping practices but also in the development of novel methods for achieving sustainable improvements in the track stability after tamping. The simulation model is developed using a commercially available DEM software called PFC3D (Particle Flow Code 3D). A detailed explanation is provided about how to set up the DEM model of railway ballast considering important parameters like selection and calibration of particle shapes, ballast mechanical properties, contact model, and parameters governing the contact force models. Tamping operation is incorporated into the simulation model using a half-track layout with a highly modular code that enables a high degree of adjustability to allow control of all process parameters for achieving optimized output. A parametric study is performed to find the best values of tine motion parameters to optimize the linear tamping efficiency and a performance comparison has been made between linear and elliptical tamping. It is found that squeeze and release velocity of the tines should be lesser for better compaction of the particles and linear tamping is better compared to elliptical tamping. / Master of Science / Railway track stability is the resistance of the tracks to deformation and is affected by the rail traffic, ballast fouling (contamination of ballast) and the changing environmental conditions. The track stability depends on the normal and frictional support provided by the ballast to the sleepers. Non-uniform ballast consolidation below the railway sleeper results in erratic wheel-rail contact forces, low traffic speeds, poor ride quality, and derailments. Thus, tamping is a railway track maintenance method done periodically on the railway tracks to ensure track stability. Tamping process involves compacting the railroad ballast underneath the sleeper. The sleeper is lifted by a desired height and then vibrating tamping tools called tines are inserted into the ballast below the sleeper to fill the void created by lifting of the sleeper and the sleeper is dropped back on to the ballast. So, it is important to understand the ballast mechanics, dynamics and ballast’s behavioral response to the tamping operation. Since, large scale experiments such as this are difficult, this operation has been simulated in a commercially available software called PFC3D using a Discrete Element Model (DEM) to represent the railway ballast. It is shown through a simulation that though spherical particles provide better computational efficiency, they cannot capture the exact ballast behavior like clumps (a collection of spherical pebbles). So using clumps to represent ballast, efforts are made to optimize the linear tamping efficiency. This is done by changing the values of parameters like tine amplitude, tine frequency, insertion velocity and squeeze velocity and finding their optimum values. Linear tamping results are compared with elliptical tamping. Thus, an optimum tamping cycle would help save money spent on the track maintenance activities.

The development of Discrete Element Model (DEM) of railway ballast for the purpose of studying the behavior of ballast particles during tamping is addressed in a simulation study, with the goal of optimizing the railroad tamping operation. A comprehensive literature review of applicability of DEM techniques in modeling the behavior of railway ballast is presented and its feasibility in studying the fundamental mechanisms that influence the outcome of railroad tamping process is analyzed. A Discrete Element Model of railway ballast is also developed and implemented using a commercially available DEM package: PFC3D. Selection and calibration of ballast parameters, such as inter-particle contact force laws, ballast material properties, and selection of particle shape are represented in detail in the model. Finally, a complete tamping simulation model is constructed with high degree of adjustability to allow control of all process parameters for achieving realistic output. The analysis shows that DEM is a highly valuable tool for studying railroad tamping operation. It has the capability to provide crucial and unprecedented insights into the process, facilitating not only the optimization of current tamping practices, but also the development of novel methods for achieving sustainable improvements in track stability after tamping in the future. Different ways of modeling particle shapes have been evaluated and it has been shown that while using spheres to represent irregular ballast particles in DEM provides immense gains in computational efficiency, spheres cannot intently capture all properties of irregularly shaped particles, and therefore should not be used to model railway ballast particles. Inter-particle and wall-particle contact forces are calculated using Hertzian contact mechanics for determining ballast dynamics during tamping. The results indicate that the model is able to accurately predict properties of granular assemblies of the railway ballast in different test cases. The developed model for simulating tamping operation on a half-track layout is expected to be extended in future studies for evaluating rail track settlement and stability, optimization of tamping process, and performance of different ballast gradations. / MS

Denna studies syfte var att identifiera vilka diskurser som blev synliga samt hur och om dessa diskurser bidrog till en process av andrefiering i Ulf Kristerssons nationaldagstal från år 2023. För att utföra studien användes två frågeställningar vars syfte var att identifiera diskurser som kan kopplas till andrefiering, samt hur dessa kan förstås utifrån en process av andrefiering. I mitt resultat och analys användes van Dijks kritiska diskursanalys och diskursstrukturer samt teorier om andrefiering och van Dijks “ingroup-outgroup-polarization”. I resultatet identifierades tre diskurser: diskurs om medborgarskap, diskurs om det svenska språket och diskurs om svenska värderingar, som kunde kopplas till en andrefiering. Ett “vi” och “dem” identifierades genom diskursstrukturer. “Viet” symboliserades med svenska värderingar, tolerans, normer och medborgarskap, till skillnad från “dem” som symboliserades som kriminella, lögnare och med avvikande värderingar. “De andra” målades upp som annorlunda “oss”. Slutsatsen i min studie är att det kunde identifieras en direkt men oftast indirekt andrefieringsprocess i Ulf Kristerssons nationaldagstal. / The purpose of this study was to identify which discourses became visible and how and if these discourses contributed to a process of otherization in Ulf Kristersson's National Day speech from the year 2023. To accomplish the study, two questions were used whose purpose was to identify discourses that can be linked to otherization, as well as how these can be understood based on a process of otherization. In my results and analysis I applied van Dijk's critical discourse analysis and discourse structures as well as theories of otherization and van Dijk's ingroup-outgroup polarization. In the result, three discourses were identified: discourse about citizenship, discourse about the Swedish language and discourse about Swedish values, which could be linked to an otherization. The study identified an "us" and "them" through discourse structures. “Us” was symbolized with Swedish values, tolerance, norms and citizenship, in contrast to "them" who were symbolized as criminals, liars and with deviant values. "The others" were portrayed as different from "us". The conclusion of my study is that the process of otherization in Ulf Kristersson's National Day speech was direct but mostly indirect.

Historical topographic maps are valuable resources for studying past landscapes, but they are unsuitable for geospatial analysis. Cartographic map elements must be extracted and digitized for use in GIS. This can be accomplished by sophisticated image processing and pattern recognition techniques, and more recently, artificial intelligence. While these methods are generally effective, they require high levels of technical expertise. This study presents a straightforward method to digitally extract historical topographic map elements from within popular GIS software, using new and rapidly evolving toolsets. A convolutional neural network deep learning model was used to extract elevation contour lines from a 1940 United States Geological Survey (USGS) quadrangle in Sevier County, TN, ultimately producing a Digital Elevation Model (DEM). The topographically derived DEM (TOPO-DEM) is compared to a modern LiDAR-derived DEM to analyze its quality and utility. GIS-capable historians, archaeologists, geographers, and others can use this method in research and land management.

The simple accumulation-based network identification method (ANIM) in a raster Geographic Information System (GIS) posed by O'Callaghan and Mark (1984) has been criticized for producing a spatially uniform drainage density (Tarboton 2002) at the watershed scale. This criticism casts doubt on the use of ANIMs for deriving properties such as overland flow length for nonpoint source pollution models, without calibrating the accumulation threshold value. However, the basic assumption that underlies ANIMs is that convergent topography will yield a more rapid accumulation of cells, and thus, more extensive flow networks, with divergent, or planar terrain yielding sparser networks. Previous studies have focused on networks that are coarser than the hill-slope scale, and have relied upon visual inspection of drainage networks to suggest that ANIMs lack the ability to produce diverse networks. In this study overland flow lengths were calculated on a sub-watershed basis, with standard deviation, and range calculated for sub-watershed populations as a means of quantifying the diversity of overland flow lengths produced by ANIM at the hill slope scale. Linear regression and Spearman ranking analyses were used to determine if the methods represented trends in overland flow length as suggested by manual delineation of contour lines. Three ANIMs were analyzed: the flow accumulation method (O'Callaghan and Mark, 1984), the terrain curvature method (Tarboton, 2000) and the ridge accumulation method (introduced in this study). All three methods were shown to produce non-zero standard deviations and ranges using a single support area threshold, with the terrain curvature method producing the most diverse networks, followed by the ridge accumulation method, and then the flow accumulation method. At an analysis unit size of 20 ha, the terrain curvature method produced a standard deviation that was most similar to those suggested by the contour crenulations, -13.5%, followed by the ridge accumulation method, -21.5%, and the flow accumulation method, -61.6%. The ridge accumulation produced the most similar range, -19.1%, followed by terrain curvature, -24.9%, and flow accumulation, -65.4%. While the flow accumulation networks had a much narrower range of predicted flow lengths, it had the highest Spearman ranking coefficient, Rs=0.722, and linear regression coefficient, R2=0.602. The terrain curvature method was second, Rs=0.641, R2=0.469, and then ridge accumulation, Rs=0.602, R2=0.490. For all methods, as threshold values were varied, areas of dissimilar morphology (as evidenced by the common stream metric stream frequency) experienced changes in overland flow lengths at different rates. This results in an inconsistency in ranking of sub-watersheds at different thresholds. When thresholds were varied to produce average overland flow lengths from 75 m to 150 m, the terrain curvature method showed the lowest incidence of rank change, 16.05%, followed by the ridge accumulation method, 16.73%, then flow accumulation, 25.18%. The results of this investigation suggest that for all three methods, a causal relationship exists between threshold area, underlying morphology, and predicted overland flow length. This causal relationship enables ANIMs to represent contour network trends in overland flow length with a single threshold value, but also results in the introduction of rank change error as threshold values are varied. Calibration of threshold value (varying threshold in order to better match observed overland flow lengths) is an effective means of increasing the accuracy of ANIM predictions, and may be necessary when comparing areas with different stream frequencies. It was shown that the flow accumulation method produces less diverse networks than the terrain curvature and ridge accumulation methods. However, the results of rank and regression analyses suggest that further investigation is required to determine if these more diverse ANIM are in fact more accurate than the flow accumulation method. / Master of Science

Undulatory locomotion is a common and powerful strategy used in nature at different biological scales by a broad range of living organisms, from flagellated bacteria to prehistoric snakes, which have overcome the complexity of living in ”flowable” media. By taking inspiration from this evolution-induced strategy, we aim at modelling the locomotion in a granular and viscous environment with the objective to provide more insights for designing robots for soil-like media exploration. Moreover, in contrast to common types of movement, the granular locomotion is still not well understood and is an open and challenging field. We approached this phenomenon with several tools: (i.) numerically, via coupling the Finite Element Method (FEM) with the Discrete Element Method (DEM) using ABAQUS; (ii.) analytically, by employing the Lagrangian formalism to derive the equations of motion of a discrete and continuous system subject to non-conservative forces, and (iii.) experimentally, by creating an ad-hoc set up in order to observe the migration of microfibres used for the treatment of spinal cord injuries. The computational attempts to model the motion in a granular medium involved the simulation of the dynamics of an elastic beam (FEM) surrounded by rigid spherical particles (DEM). A propulsion mechanism was introduced by sinusoidally forcing the beam’s tip normally to the longitudinal axis, while the performance of the locomotion was evaluated by means of a parametric study. Depending on the parameters of the external excitation, after a transient phase, the slender body reached a steady-state with a constant translational velocity. In order to gain physical insights, we studied a simplified version of the previous continuous beam by introducing a discrete multi-bar system. The dynamics of the latter was analytically derived, by taking into account the forces exchanged between the locomotor and the environment, according to the Resistive Force Theory. By numerically solving the equations of motion and evaluating the input energy and dissipations, we were able to define the efficiency and thus provide an effective tool to optimise the locomotion. It is worth mentioning that the two approaches, despite the different physical hypothesis, show a qualitatively and quantitatively good accordance. The numerical and analytical models previously analysed have shown promising results for the interpretation of "ad-hoc" experiments that demonstrate the migration of a microfibre embedded in a spinal cord-like matrix. This migration needs to be avoided, once the regenerative microfibre is implanted in the lesioned spinal cord, for the sake of the patients health.

I denna undersökning har jag haft som syfte att undersöka hur media beskriver tre områden byggda under miljonprogrammet: Lindängen, Nydala och Rosengård och dess invånare med utgångspunkt från Sydsvenskan och Aftonbladet. Detta har gjorts med hjälp av kritisk diskursanalys samt tidigare forskning och teorier. Utifrån de fem olika teman, miljö och arkitektur, levnadsmiljö, utbildning och arbetslöshet, kriminalitet och brott samt Vi och dem har jag försökt skapa en så bred bild som möjligt. Studiens övergripande slutsats är att dessa områden konsekvent beskrivs i termer som betonar socioekonomisk utsatthet, kriminalitet och problematiska samhällsförhållanden. Invånarna framställs som bristande i hygien, med låg utbildningsnivå och utländsk härkomst. Beskrivningar som dessa förstärker negativa stereotyper och bidrar till en bild av områdena och dess invånare som avvikande och separerade från resten av samhället. / In this paper I have sought to investigate how media portrays three different boroughs inMalmö city built up during the so-called “million programme”, namely: Lindängen, Nydalaand Rosengård and its residents, based on the publications of the newspapers Sydsvenskanand Aftonbladet. The means used for the investigation are mainly critical discourse analysiscoupled with previous research and theories. In order to achieve a broad description of theproblem, this paper has centered around the five central themes of: environment &architecture, living environment, education & worklessness, criminality & crime and “Weand them”. The resulting conclusion of this study is that the three named burroughs areconsistently portrayed in the aforementioned media outlets as areas overrun bysocioeconomic degradation, criminal activity and problematic societal relationships. Theresidents are portrayed as lacking in hygiene, with a low level of education, and of foreignorigin.These types of descriptions in media enhance negative stereotypes and contribute to animage of these areas as containing inhabitants which are deviant and isolated from society asa whole.

Under de senaste åren har omvärlden varit fylld av våldsamma konflikter, till följd av detta har miljontals människor flytt sina hem. Kriget i Syrien och den ryska invasionen av Ukraina har lett till att tusentals flyktingar sökt skydd i Sverige. Tidigare forskning kring invandring i tryckpress har påvisat att den generella inställningen gentemot flyktingar varit negativ. Syftet med uppsatsen utgår från denna kontext och söker svar på följande frågeställning: Hur konstrueras diskursen kring syriska och ukrainska flyktingar i Dagens Nyheter? Vilka subjektspositioner möjliggörs? samt Hur framställs och representeras dessa i diskursen utifrån ett ”vi och dem” perspektiv? Utifrån en diskursinspirerad innehållsanalys har jag totaltanalyserat 24 artiklar publicerade i Sveriges främsta morgontidning Dagens Nyheter, baserat på de två tidsperioderna som respektive flyktinggrupp flydde till Sverige. Genom diskurs- ochrepresentationsteorier fann jag att framställningarna av syriska- och ukrainska flyktingarskilde sig åt avsevärt utifrån ett ”vi och dem” perspektiv. Den förra skildrades som ett ”problem” som krävde restriktiva, politiska handlingar och den senare som ”jämlik” och priviligierad. Således visar min undersökning hur dessa två flyktinggrupper tilldelas skilda positioner inom samma diskurs, vilket praktiskt taget, avgör deras handlingsmöjligheter i Sverige. / In recent years, the world has been filled with violent conflicts, hence millions of people have fled their homes. The war in Syria and the Russian invasion of Ukraine have led to thousands of refugees seeking refuge in Sweden. Previous research on immigration in the print press hasshown that the general attitude towards refugees has been negative. The purpose of the essay is based on this context and seeks answers to the following questions: How is the discourse around Syrian and Ukrainian refugees constructed? Which subject-positions are enabled? and How are these portrayed and represented within the discourse based on an “us and them” perspective? Based on a discourse-inspired content analysis, I have analyzed a total of 24 articles published in Sweden's most prominent morning newspaper, Dagens Nyheter, during the two time periods of which each refugee group fled to Sweden. Through discourse and representation theories, I found that the representations of Syrian and Ukrainian refugees differed significantly from an "us and them" perspective. The former was portrayed as a "problem" that required restrictive, political actions and the latter as "equal" and privileged. Thus, my research shows how these two refugee groups are assigned different positions within the same discourse, which determines their possibilities for practical action in Sweden.

Yes / Numerical simulation of wet granulation in a continuous granulator is carried out using Discrete Element Method (DEM) to discover the possibility of formation of seeded granules in a continuous process with the aim of reducing number of experimental trials and means of process control. Simple and scooped drum granulators are utilized to attain homogenous seeded granules in which the effects of drum rotational speed, particles surface energy, and particles size ratio are investigated. To reduce the simulation time a scale-up scheme is designed in which a dimensionless number (Cohesion number) is defined based on the work of cohesion and gravitational potential energy of the particles. Also a mathematical/numerical method along with a MATLAB code is developed by which the percentage of surface coverage of each granule is predicted precisely. The results show that use of continuous granulator is promising provided that a high level of shear is considered in the granulator design, e.g. it is observed that using baffles inside the drum granulators is essential for producing seeded granules. It is observed, moreover, that the optimum surface energy for scooped granulator with rotational speed of 50 rpm is 3 J/m2 which is close to the number predicted by Cohesion number. It is also shown that increasing the seed/fine size ratio enhances the seeded granulation both quantitatively (60% increase in seeds surface coverage) and qualitatively (more homogeneous granules).