This thesis explores and develops a simulation model for Line of Sight(LoS) Multiple-Input Multiple-Output (MIMO) systems in complex environments. The focus will be on implementing a 2 × 2-MIMO system in order to study phase differences of the received signals. The propagation of the electromagnetic waves is based on an existing wave propagation model that uses the parabolic equation approach. This work aims to deepen our understanding of a 2 × 2-MIMO systems’ behavior under various conditions, including free space propagation but also standard atmospheric and ducting environments. The results demonstrate that the parabolic equation method aligns well with theoretical expectations, validating its use for modeling MIMO systems.The findings have significant implications for optimizing the design and operation of wireless communication systems. The thesis also outlines potential future work, including empirical model verification, development of alternative models, and extension to more complex MIMO systems.

No description available.

In this master thesis we investigate implications of the Domain-Wall/Cosmology (DW/C) correspondence on one-point functions of holographic RG-flows. The thesis gives a detailed computation of linearized gauge-invariant Einstein equations in (d+1) dimensions while making the DW/C correspondence explicit. Although holographic renormalization has previously been studied on Lorentzian manifolds, we extend its study to Lorentzian domain-wall solutions with a parameter η. This parameter is introduced to easily travel from domain-walls to cosmologies in the context of the DW/C correspondence. We present the calculation of the vacuum expectation value of general scalar boundary operators of conformal weight Δ dual to a (d+1)-dimensional bulk theory, while still making the DW/C correspondence appear explicitly. Finally, we study the application of these results to holographic RG-flow solutions. In particular, the GPPZ solution is investigated in the framework of the thesis. We find that the vacuum expectation value of the scalar field is invariant under the domain-wall/cosmology correspondence.

In a celebrated series of experimental observations, starling flocks have been shown to be characterized by scale-free, long-ranged spatial correlations in their velocity fluctuations. While this is expected for velocity orientation correlations on the basis of simple symmetry-breaking arguments, the same scaling-free behaviour for speed (i.e. the absolute value of birds’ velocity) correlations cannot be explained by the same symmetry-based argument. Possible explanations so far put forward required the implicit or explicit fine-tuning of a speed control parameter. In this work we explore a different possibility, investigating the effects of the experimental discrete temporal sampling of individual bird trajectories. We argue that observed velocity may well be a time coarse-grained observable, that is, the sum over many faster course corrections taken by the bird. A simple argument shows such a time coarse-grained speed to be linked with the squared fluctuations of (soft modes) transversal velocities, which may thus acquire a long-range correlation. Our idea is numerically tested by measuring spatial correlations between coarse-grained speeds in the on-lattice equilibrium XY model and the off-lattice out-of-equilibrium Vicsek model in two dimensions. Saturation of the speed correlation length is found in the equilibrium XY model, while in the non-equilibrium Vicsek model ordered symmetry-broken phase shows scale-free behaviour with a correlation length ξ is found to be proportional to system size L. We conclude that in non-equilibrium flocking models, the temporal coarse-graining procedure is able to reproduce scale-free behaviour at system sizes which are relevant to the experimental observations. We believe that this mechanism might find applications beyond the case of starling flocks and perhaps be relevant for other experimental observations of collective motion.

Water contamination through substances called per- and polyfluoroalkyl substances (PFAS) is a worldwide problem. Being able to measure the concentrations of PFAS in water is a first step towards beating this contamination. One alternative is to use a field test kit instead of extensive lab equipment to monitor the contaminated areas. This thesis has investigated the possibility of using amine-functionalized mesoporous carbon as adsorbent to develop a detection method based on adsorbing first PFAS and then dye in aqueous solutions. The non-adsorbed dye concentrations are depending on the amount of PFAS, and hence the colour intensity in the remaining solution is proportional to PFAS concentration. Mesoporous carbon with amine functional groups were chosen as specific adsorbents for PFAS because of its large surface area and high adsorption capacity. It has been shown that some colorants would react in a similar way as PFAS on sorbents and thus can be used as an indicator for the user. In the study, the two most common PFAS, PFOA and PFOS, were studied and Rose Bengal was the dye. The adsorbent’s morphology, pore structure and pore size was verified with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption before being tested. Adsorption tests were performed using different PFAS concentrations and a dye solution range in order to find three things: the detection range, the ratio powder/solution in order to see a difference, and the adsorption or saturation time for both PFAS and dye. This thesis concluded that even though the adsorbent was not as efficient as predicted, this method could be used for detecting PFAS concentrations down to at least 0.1 pg/ml and could be a possible approach for quick field tests in the future.

This thesis is about thwo papers related to extra dimensions. Paper A discusses extrinsic curvature effects, and paper B treats symmetries of supersymmetric membranes. In the part of this thesis related to paper A, we extend the theory of non-relativistic quantum particles confined to submanifolds to relativistic boson fields. We show that a Klein-Gordon field constrained to a submanifold of a Lorentzian manifold experiences an induced potential similar to the one for the Schr{\"o}dinger equation. We embedd the Schwarzschild solution and the Robertson-Walker space-time and derive the induced potentials. Possible physical consequences of these induced potentials are also discussed. The second part is related to paper B, we study the dynamics of supersymmetric membranes, which are higher dimensional generalizations of supersymmetric strings. We derive a supersymmetric analogue of a dynamical symmetry for bosonic membranes. / QC 20110427

Special relativity is a subject that attracts interest among students, but there are many things that make students experience it as difficult. As a physics teacher, it is important to both have a solid base of knowledge in physics as well as educational knowledge within the subject. You need to know what students usually struggle with, which parts to focus on to give the students a good understanding of physics, et cetera. This project is a literature study that examines special relativity in four parts. The first part of the project is a historical description of special relativity, summarizing how researchers have concluded the theory of special relativity. It consists of a series of experiments and hypotheses before Einstein tied everything together with his theory of special relativity. Then the central ideas of special relativity are described, with a focus on exercises that describe relativistic phenomena. The ideas covered in this second part are the relativity of simultaneity, time dilation, length contraction and mass and energy equivalence. The third part consists of a summary of current educational research to explore different ways to teach special relativity, according to the educational research. Many students make up their own explanations when presented with a relativistic phenomenon, that matches their Newtonian view in mechanics. It is a challenge to get students to think in a new relativistic way. A common difficulty is to move between different reference systems, which is necessary since relativistic phenomena in movement is only visible when looking at the same movement from different reference system. For the last part of the project, the Swedish curriculum and Swedish textbooks are examined. The section on relativity often begins with what students struggle most with, moving between frames of reference. Before introducing special relativity, it is useful to practice switching between different reference systems in classical mechanics, using Galilean transformations and relative motion. Another idea might be to introduce special relativity with, for example, the equivalence in mass and energy, where students do not encounter the problem with reference systems. / Speciell relativitetsteori är något som väcker nyfikenhet hos elever, men det finns mycket som gör att eleverna upplever det som svårt. Som lärare är det viktigt att ha en gedigen ämneskunskap och mycket didaktisk kunskap. Man måste ha koll på vad eleverna brukar ha svårt för, vilka delar man bör fokusera på för att eleverna ska få en bra grund, med mera. Det här projektet är en litteraturstudie som undersöker speciell relativitetsteori i gymnasieskolan i fyra delar. Första delen i projektet är en historisk beskrivning av speciell relativitetsteori, hur forskare har kommit fram till den speciella relativitetsteorin. Historiebeskrivningen består av en serie experiment och hypoteser innan Einstein knöt ihop säcken med den speciella relativitetsteorin. Sedan beskrivs de centrala idéerna inom relativitetsteori, med fokus på många exempel som beskriver relativistiska fenomen. De delar som behandlas i det här projektet är relativiteten i simultanitet, tidsdilatation, längdkontraktion samt massa- och energiekvivalens. Den tredje delen består av en sammanfattning av modern fysikdidaktisk forskning, för att ta reda på hur man kan undervisa forskningsbaserat inom speciell relativitet. Elever skapar ofta egna förklaringar till relativistiska fenomen, som stämmer bättre överens med en Newtonsk uppfattning. Att få eleverna till ett nytt relativistiskt tankesätt är en utmaning. Det som elever främst har svårt med är att gå mellan olika referenssystem, vilket är nödvändigt för att uppfatta relativistiska fenomen inom rörelse. Till sist undersöks den svenska läroplanen och svenska läroböcker. Ofta börjar avsnittet om relativitetsteori med det elever har som svårast för, att gå mellan olika referenssystem. Innan speciell relativitetsteori introduceras är det bra att öva att gå mellan olika referenssystem inom klassisk mekanik, arbeta med relativ rörelse och Galileitransformationer. En annan idé kan vara att introducera speciell relativitetsteori med till exempel ekvivalensen i massa- och energi, där eleverna inte stöter på det problemet.

The purpose of the study is to contribute knowledge about children's understanding of the physical phenomenon of friction by conducting a planned learning activity together with the children. In the activity, the children had the opportunity to investigate high and low friction with varied materials in a slide. A total of seven five-year-old children participated on two separate occasions. The observations were carried out at the respective preschool's slide, where the children had to ride with the different materials and investigate the friction that arose. The observations were recorded with audio and video recording, which were then analysed using a content analysis and based on the theory of variation. The results of the study indicate that most children had a certain understanding of the phenomenon of friction even before the activity, but not of the scientific concepts or knowledge enough to explain their thoughts about the phenomenon. The results also showed that the design of the learning activity contributed to an increased understanding of the phenomenon of friction. They developed their thoughts and explanations about the phenomenon in relation to the different materials that were investigated and several of the children also adopted the concept of friction towards the end of the activity. Key words: friction, research method, variation theory, preschool / Studiens syfte är att bidra med kunskap kring barns förståelse för det fysika-liska fenomenet friktion genom att genomföra en planerad lärandeaktivitet till-sammans med barnen. I aktiviteten fick barnen möjlighet att undersöka hög och låg friktion med olika material i en rutschkana. Det deltog totalt sju femå-riga barn vid två olika tillfällen. Observationerna genomfördes vid respektive förskolas rutschkana där barnen fick åka med de olika materialen och under-söka friktionen som uppstod. Observationerna spelades in med ljud och vide-oinspelning som sedan analyserades med hjälp av en innehållsanalys och uti-från variationsteorin. Resultatet av studien tyder på att de flesta barn hade en viss förståelse för fenomenet friktion redan innan aktiviteten, men dock inte för de vetenskapliga begreppen eller kunskaper tillräckligt för att förklara sina tankar kring fenomenet. I resultatet framkom även att utformningen av läran-deaktiviteten bidrog till en ökad förståelse för fenomenet friktion. De utveck-lade sina tankar och förklaringar om fenomenet i relation till de olika materi-alen som undersöktes och flera av barnen anammade även begreppet friktion mot slutet av aktiviteten.

Liquid-liquid phase separation (LLPS) is an important phenomenon in soft condensed matter that explains many properties of membraneless organelles in living cells. The research on this topic is, therefore, a field with a wide range of applications such as biopharmacy and biomaterials. In this project, we investigate the LLPS of the antibody protein Immunoglobulin G (IgG) by analyzing the liquid dynamics of IgG solutions at a wide range of temperatures with dynamic light scattering (DLS). It was found that the slow component of the autocorrelation function increases with decreasing temperature below 0 °C. This can be attributed to either the number of protein clusters increasing as the sample approaches phase separation or LLPS droplets forming in the solution. LLPS was detected through optical microscopy, visualising the droplet formation in the IgG solution. This work confirms that LLPS can be detected for bovine IgG solutions without the presence of cosolvents and without water freezing in the sample.

In this thesis we study multipole moments of axisymmetric spacetimes. Using the recursive definition of the multipole moments of Geroch and Hansen we develop a method for computing all multipole moments of a stationary axisymmetric spacetime without the use of a recursion. This is a generalisation of a method developed by Herberthson for the static case. Using Herberthson’s method we also develop a method for finding a static axisymmetric spacetime with arbitrary prescribed multipole moments, subject to a specified convergence criteria. This method has, in general, a step where one has to find an explicit expression for an implicitly defined function. However, if the number of multipole moments are finite we give an explicit expression in terms of power series. / <p>Note: The two articles are also available in the pdf-file. Report code: LiU-TEK-LIC-2006:4.</p>