This project revolves around a monostatic time of flight LiDAR, monostatic meaning that the emitted light and the incoming light are collocated and LiDAR being an acronym for light detection and ranging. The goal here is to explore and understand the principles of the LiDAR whilst also finding its advantages and shortcomings. One expected shortcoming is that of the effects of light scattering of the laser. To mitigate these effects a short laser pulse is desired without compromising on the power output. In order to reduce the pulse width the electronics of the LiDAR needed to be understood and two approaches emerged. The first revolved around simplifying the electronic schematics of the LiDAR to the point it could be described as a simple RLC-circuit and solving for the current analytically. The other approach was to simulate it using the simulation software LTspice.

The results from the analytical approach and the LTspice simulation showed clear ways of how the pulse width could be decreased by altering the onboard resistance, inductance and capacitance. The easiest alternative was to simply reduce the capacitance, however this resulted in a lower power output. But these effects could be mitigated by simply increasing the applied voltage. However it was also discovered that the analytical and LTspice simulations were not entirely correct in their attempts to simulate the real behavior of the laser drive boards within the LiDAR.

To study the effects of the scattering two theories were studied, namely Rayleigh and Mie scattering. The influence of Rayleigh scattering was quickly determined to be negligible but the Mie scattering results showed that it will definitely affect the LiDAR, even though the Mie scattering influence was extremely over exaggerated.

In the 1970s, the tandem shaped charge was developed to overcome countermeasures like active armor and thicker armor. It uses a leading charge to clear a path for the main trailing charge, theoretically improving penetration. However, disturbances from shock waves can cause under-performance. To address this, the leading charge's shock waves must be minimized to protect the main charge. Designing a part with shock wave attenuating properties can help achieve this.There is limited information on grenade structures that reduce shock wave stresses from impact and detonation. Most studies on shock wave attenuation focus on protecting buildings and humans, with few addressing structures designed to withstand and then halt the transmission of shock waves.

Here we report on simulations in IMPETUS Afea where an explicit FEM solver approach have been made to compare four different concepts to an original structure. Physical theories about attenuation of shock waves in solids has been applied. The first concept utilize a mass with different area increases in the propagation path of the shock wave. The second concept use the characteristics of interfaces between two different materials, with different shock wave impedance which will reflect and transmit the incoming wave. The third concept incorporate a brittle ceramic which should shatter when a shock wave propagates to it, if the brittle structure fracture, no more shock waves can be transmitted. The fourth concept utilize the properties of porous metals. All concepts shows shock wave attenuating effects, but only the third concept which totally disconnects the leading shaped charge to the main charge might be a full solution. The fourth concept compared to the third has other advantages, it attenuate the shock wave to more than 90%, not halt the transmission. Configuration of the porosity in the structural part can be made to have characteristics that can solve the problem. Concept three and four are the main recommendations for a feasibility study.

The exploding foil initiator (EFI) is a high voltage detonator used to initiate explosions. It is designed to improvesafety standards by lowering the risk of accidental detonation and in doing so allows for in-line integration in, forexample, weapon systems that minimizes their complexity and thus reduces the number of possible failures. It ishighly reliable in terms of timing and avoids that functionality of the detonator deteriorates over time, which has beena problem in earlier designs of detonators. This thesis aims to develop an understanding of each part of the initiationprocess by means of computer simulations. The proportions of the electrically conducting bridge is varied in order tofind relations that optimize the design. Success depends on the simulated pressure generated inside a hexanitrostilbene(HNS) primer.The results showed that increasing the dimensions of the bridge greatly affects the pressure produced in the primer,but its proportions were still important. Unfortunately the simulations of the electrical explosion and the accelerationof the flyer suffered from convergence issues that rendered the flyer’s velocity graphs incomplete. But even with theseshortcomings, thanks to empirical data from earlier studies that analysed EFI prototypes, it was possible to makepredictions about the success of various set ups. The information gathered in this thesis should serve as a foundationfor future development of computer models of the EFI technology that will aid the production of prototypes that meetthe specific requirements.i   

A key aspect of understanding the impact of ballistic projectiles on a target is understandingthe dependence of the hole diameter and residual velocity on parameters like initial velocity,mass of the projectile, the geometry of the projectile, and thickness of the target plate.Ideally, simulation tools can be used to study this concept. Physical testing can be expensiveand slow, and it is often difficult to visualize what happens in an experiment.

However, in simulation, these models can contain errors or may not account for relevantphysics, so one needs to be cautious with the results. We determined the hole diameterand residual velocity for projectile impact on steel and concrete plates. These results werecalculated by conducting simulations and independently from empirical formulas found inthe literature. The comparison reveals the accuracy of different formulas.

The study reveals notable discrepancies between empirical formulas and numerical simula-tions for residual velocity in concrete, Furthermore in the case of steel the empirical formulas agrees more with numerical simulation. These formulas offer limited general applicabilityand only provide rough approximations. However, they align more closely with simulationsin predicting residual velocity, despite a small margin of error. Certain formulas, like theThor formula at an initial speed of 2000 m/s and considering the angle are notably morereliable, suggesting their potential use as affordable alternatives to numerical simulations.

The present study proposes a novel approach to Coverage Path Planning for unmanned aerial vehicle (UAV) inspired by the Orienteering Problem. The main goal is to develop an algorithm suitable for Search and Rescue Missions, which can produce a search pattern with dynamical constrains, that is not limited to the traditional back-and-forth motion or spiral patterns. This method leads to a more flexible and diverse coverage of the Area of Interest. In order to generate dynamically correct trajectories, we utilize cubic splines as motion primitives to solve the Orienteering Problem. To accomplish this, we implement and test three different types of cubic splines, namely Catmull-Rom, Freya, and B-splines. To determine the coverage of the search area, the sensor's projection (footprint) is evaluated along the spline trajectory onto a costmap. This method accounts for the footprint's orientation and size, which depend on the UAV's attitude to some extent. This version of the Orienteering Problem using splines for dynamical control and calculating coverage, we call the Mapping Motion Orienteering Problem (MMOP). \\The heuristic method Simulated Annealing is used to address the combinatorial challenges of the MMOP, and two cost functions are tested for optimization. The study shows that the choice of spline has a significant impact on the algorithm's efficacy, and B-splines are the most effective in generating dynamic and adaptable trajectories. However, the study also shows that the Simulated Annealing algorithm with identical settings produced varied resulting paths. Finally, further research is needed to solve the challenges faced with the computational time, which heavily depends on factors such as the sampling rate for the footprint along the path and the resolution of the costmap and footprint itself.

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.

The aim of this thesis is to examine the hard $S$-matrix for QED and QCD, due to Hannesdottir and Schwartz [1], both recreating known results, and finding new results in lower dimensions. Electrons by themselves are not gauge invariant, and in the massless limit do not give finite $S$-matrix elements for individual processes; one needs to add together seemingly arbitrary combinations of diagrams in order to be able to calculate the scattering cross-section. One remedy is to exchange the bare electron for a dressed state, or equivalently to include the dressing in the $S$-matrix itself. This gives rise to a formalism in which one needs only consider time cuts of an individual diagram in order to find finite $S$-matrix elements. The main result of this thesis is the examination of the results which are found by Hannesdottir and Schwartz in a model system of fewer dimensions. This may be of use for toy model calculations in QCD, where 2+1-dimensional QED better models certain phenomena than does 3+1-dimensional QED.

Organic solar cells (OSCs) based on non-fullerene acceptors (NFAs) have attracted a great deal of attention in recent years due to their rapidly increasing efficiency and enormous potential. In this work, the optical and electronic properties of systems containing the very promising non-fullerene acceptor PYT have been thoroughly studied with the use of the density functional theory (DFT) and the time-dependent density functional theory (TDDFT). By changing the electron linker from thiophene to furan and selenophene, respectively, the PYT was divided into three variants, each of which was studied independently. In addition, these three systems were combined with the donor PBDB-T to generate two distinct interface conformations. The properties studied in this work include the optimized geometries, HOMO-LUMO levels, UV-Vis spectra, frontier molecular orbitals (FMOs), natural transition orbitals (NTOs), density of states (DOS), dipole moments, open-circuit voltages, exciton binding energies, and local exciton (LE) and charge transfer (CT) energies. The calculations were performed in chlorobenzene solution utilizing the polarizable continuum model (PCM). It was discovered that PBDB-T/PY-Se exhibited remarkable flatness employing the π-π stacking conformation which corresponds well with the excellent D/A compatibility observed experimentally. All interfaces displayed appropriate positioning of the HOMO-LUMO levels, with the acceptor dominating the LUMO and the donor dominating the HOMO, with HOMO-LUMO gaps ranging between 1.34 and 1.38 eV. The differences in the interchanging of the electron linker were not that significant, and neither was the change in interface conformation in terms of the HOMO-LUMO levels. This may indicate that the system can be effective even without the presence of a π-π stacking conformation. The first excited states for all interface systems were shown to be pure CT transitions, and on average, 80% of the states exhibit CT character. The remaining contributions consisted of transitions within the pure materials, with a larger contribution within the acceptor. The theoretical results of this study indicate that systems containing the novel polymer acceptor PYT and its variants PY-O and PY-Se exhibit very intriguing properties, and further development of OSCs containing these polymers might further aid in the development of high-performance OSCs.

Non-fullerene Acceptors (NFAs) have gathered a great deal of interest for use inorganic photovoltaics (OPVs) due to recent breakthroughs in their power conversion efficiency and other advantages they offer over their Fullerene-based counterparts.

In this work, a new promising non-fullerene polymer acceptor, PF5-Y5, have been studied using density functional theory and time-dependent density functional theory; and the effects that oligomer length, geometry relaxation and exchange-correlation interaction has on the exciton binding energies (the difference between optical and fundamental energy gaps) have been investigated.

Both the fundamental and optical gaps are significantly affected by the choice of functional (i.e., the description of the exchange-correlation interaction). However, it does not appear to significantly impact obtained exciton binding energies as the effects of the fundamental and optical gaps cancel each other out.

Both the fundamental and optical energy gap are shown to slightly reduce as a function of the oligomer length (~0.1 - 0.3 𝑒𝑉 reduction for each repeated monomer). As both gaps are reduced by a similar amount per repeated monomer, they counteract each other and the total effect that oligomer length has on the exciton binding energy is very low.

Geometry relaxation and thermal effects showed the largest impact on the fundamental gap and exciton binding energy, with their combined effect resulting in a ~0.5 𝑒𝑉 reduction in binding energy. 

The fifth generation of mobile internet is upon us, but still, there is work to do before the new technology is fully utilized. The new generation of cellular network promises frequencies ranging from the sub – 6 GHz to 39 GHz, the latter being in the mmWave spectrum. At these frequencies, we can utilize geometrical optics to calculate the radio wave propagations. The purpose of this work is to explore how raytracing can be used to predict wireless radio wave channels and pathloss in indoor and urban environment settings. The model presented in this work explores line of sight, reflection, refraction, diffraction and scattering. The model utilizes Frii’s pathloss model for pathloss in the line-of-sight case. For reflection and refraction, Snell’s laws of reflection and refraction were used. For diffraction, the uniform theory of diffraction was used, and the scattering explored in this work was created using a physics based bidirectional reflectance diffusion function. With this we create a basic raytracing program for simple environments with potential for expansion in future work. The simple environment is a cube made in an STL file. The algorithms for the different parameter were a hybrid method of shoot- and bounce and image method for reflection, a double counting method for refraction. The transitions between different shadow boundaries were smooth. While scattering was explored, more work needs to be done to implement scattering into the code.

Prediction of initial velocity of artillery system is a feature that is hard to determine with statistical and analytical models. Machine learning is therefore to be tested, in order to achieve a higher accuracy than the current method (baseline). An ensemble approach will be explored in this paper, centered around feed forward deep neural network and random forest regression. Furthermore, collinearity of features and their importance will be investigated. The impact of the measured error on the range of the projectile will also be derived by finding a numerical solution with Newton Raphsons method. For the five systemstest data was used on, the mean absolute errors were 26, 9.33, 8.72 and 9.06 for deep neural networks,random forest regression, ensemble learning and conventional method, respectively. For future works,more models should be tested with ensemble learning, as well as investigation on the feature space for the input data.

In this thesis we derive a coupled system of Cahn-Hilliard equations posed in a domain with moving boundary using arguments from thermodynamics. The physical setting we have in mind is a ternary solution observed during one species evaporation as a moving boundary problem. The mixture is made of two types of polymers blended in a solvent that is allowed to evaporate at part of the surface of the domain. After formulating the evolution system as a moving-boundary problem with kinetic interface condition, we fix the moving boundary to facilitate a suitable numerical approximation. We project the resulting model equations on a finite element space and then integrate the obtained system in Python using FEniCS. We show numerically the formation of morphologies and track the evolution of the remaining solvent and of the moving boundary position. The conjecture is that such a system would produce phase separation and that the resulting morphologies are mappable to the observations of organic solar cells. Finally, we study the effect of the most relevant parameters on the output of our Cahn-Hilliard system, particularly on the speed of the moving boundary and of the morphology formation.

Renewable energy is required for a sustainable future and one way to meet this is with organic solar cells (OSCs). The OSC can be easily manufactured at a low cost, be lightweight and be used on flexible surfaces. If the efficiency in high illumination intensities and stability in harsh environments increase for OSCs, they can com- pete with the other technologies even in outdoor conditions. Another advantage of OSCs is their good performance under low-light and indoor conditions. This is utilized by Epishine, a Swedish company based in Linköping working with small, thin and flexible organic printed solar cells optimized for indoor applications. The goal of this thesis is to determine how Epishine’s solar cells for low-light indoor usage work in more challenging conditions and to identify which are the factors that are detrimental for the lifetime of the cells. The result showed that all modules had a similar initial electrical performance which indicates that the modules have high reproducibility and degradation in darkness is negligible (since the initial measurements were made at different times). The tests showed that the temperature affected the modules. The test in the oven showed a little less than half the degradation compared to tests under the solar simulator, although both tests were subjected to the same temperature. The hu- midity test and the test exposed to LED-light showed almost no degradation. For the levels exposed to the sun or simulated sunlight, the decrease of the short circuit current density shows a burn-in time, which is typical for organic solar cells. After the first couple of hours, the decrease slows down to a more linear behaviour. All modules that were exposed to bright light also showed some recovery effect for short circuit current density and efficiency after they have been kept in the dark. It would be interesting to investigate the behaviour of the modules after even more exposure and look into how the recovery effect works.

In industrial environments, operators are exposed to polluted air which after constant exposure can cause irreversible lethal diseases such as lung cancer. The current air monitoring techniques are carried out sparely in either a single day annually or at few measurement positions for a few days.In this thesis a theory-guided data science (TGDS) model is presented. This hybrid model combines a steady state Computational Fluid Dynamics (CFD) model with a machine learning model. Both the CFD model and the machine learning algorithm was developed in Matlab. The CFD model serves as a basis for the airflow whereas the machine learning model addresses dynamical features in the foundry. Measurements have previously been made at a foundry where five stationary sensors and one mobile robot were used for data acquisition. An Echo State Network was used as a supervised learning technique for airflow predictions at each robot measurement position and Gaussian Processes (GP) were used as a regression technique to form an Echo State Map (ESM). The stationary sensor data were used as input for the echo state network and the difference between the CFD and robot measurements were used as teacher signal which formed a dynamic correction map that was added to the steady state CFD. The proposed model utilizes the high spatio-temporal resolution of the echo state map whilst making use of the physical consistency of the CFD. The initial applications of the novel hybrid model proves that the best qualities of these two models could come together in symbiosis to give enhanced characterizations.The proposed model could have an important role for future characterization of airflow and more research on this and similar topics are encouraged to make sure we properly understand the potential of this novel model.

We present a novel modelling approach for the morphology formation from ternary mixtures upon evaporation, which takes into consideration two different length scales of the interaction, and further allows for these length scales to be altered. A quantitative study of the interfacial energy hints towards the existence of a mesoscopic regime - further research is needed to verify the validity of this claim however. We also demonstrate that the solvent initially follows a Fickian law of diffusion, then deviates from this behaviour, presumably due to the phase separated regions produced by the two remaining (active) components. We also attempt to bridge the gap between this work and a hypothetical three-dimensional model by considering a top-down view of the system. Here, we observe domain growth dominated by Ostwald ripening, with some coalescence. The domain growth was further characterised using Fourier image analysis.

Topological insulators are materials with their electronic band structure in bulk resembling that of an ordinary insulator, but the surface states are metallic. These surface states are topologically protected, meaning that they are robust against impurities. The topological phenomena of three dimensional topological insulators can be expressed within topological field theories, predicting axion electrodynamics and the topological magnetoelectric effect. An experiment have been suggested to measure the topological phenomena. In this thesis, the underlying theory and details around the experiment are explained and more detailed derivations and expressions are provided.

Topological insulators and topological crystalline insulators are materials that have a bulk band structure that is gapped, but that also have toplogically protected non-gapped surface states. This implies that the bulk is insulating, but that the material can conduct electricity on some of its surfaces. The robustness of these surface states is a consequence of time-reversal symmetry, possibly in combination with invariance under other symmetries, like that of the crystal itself. In this thesis we review some of the basic theory for such materials. In particular we discuss how topological invariants can be derived for some specific systems. We then move on to do band structure calculations using the tight-binding method, with the aim to see the topologically protected surface states in a topological crystalline insulator. These calculations require the diagonalization of block tridiagonal matrices. We finish the thesis by studying the properties of such matrices in more detail and derive some results regarding the distribution and convergence of their eigenvalues.

In this work, regression models for the wake field entering a propeller at certain axial andnominal position have been proposed. Wakes are non-uniform flows following a body immersedin a viscous fluid. We have proposed models for the axial and tangential velocity distribution asfunctions of ship hull and propeller measures. The regression models were modelled using Fourierseries and parameter estimations based on skewed-Gaussian and sine functions. The wake fieldis an important parameter in propeller design. The regression models are based on experimentaldata provided by the Rolls-Royce Hydrodynamic Research Center in Kristinehamn. Also we havestudied the flow in the axial velocity distribution in the propeller plane using the coherent structurecoloring method. The coherent structure coloring is used to study coherent patterns by looking atfluid particle kinematics. Using this type of analysis, we observed that the velocity distributionbehaves kinematically similar in the different regions of the wake distribution, which according tothe coherent structure coloring indicate coherence.

In rolling applications it is critical to be able to control the flatness of the metal strip. An uneven strip may in the most extreme cases lead to strip breaks. One of the systems used to measure the flatness consists of a measuring roll, which the strip is deflected over. During the contact time, heat is transferred from the hot strip to the roll. The roll is not allowed to get too hot due to risks of overheating the electronics. Previously the measuring roll have only been used in cold rolling applications, where this is usually not a problem. There is now an increased interested in using the roll in more extreme applications with higher strip temperatures. This requires knowledge about all the potential heat sources present in the system. The subject of this thesis work has been to investigate some of the contributions to the thermal balances of the measuring roll. A numerical model has been developed to describe conductive heat transfer between the metal strip and the measuring roll. Using the numerical model, the heat transfer was obtained as a function of the temperature, contact time and thickness of the strip. From these simulations a heat transfer coefficient associated with an external cooling demand was derived. The flatness measuring roll is equipped with pressure sensitive sensors used to measure the flatness of the strip. These sensors are located in internal channels and generate heat through resistive heating. The impact of this on the overall temperature of the roll was determined to be small. In the internal channels there is also a flow of air. In normal operation scenarios the flow is very low, leading to a small cooling capacity. From the thermal balance of the system it was concluded that the dominant heat source was the heat transfer between the strip and roll. This heat transfer is however heavily dependent on material properties and surface characteristics. The model used to describe the conductive heat transfer assumes no contact resistance between the strip and roll. This provides an upper-bound estimate of the heat transfer. If the contact resistance is included within the model the impact of the individual heat sources increases. Both the material properties and contact resistance requires further investigation. Combining the results of M. Gustafsson (Master of Science thesis, Karlstad University, 2018), a thermal balance for the measuring roll has successfully been developed. This balance clarifies the critical parameters which should be considered when designing the external cooling of the roll.

Devices for measurement of flatness in rolling mills is important to ensure high quality products and fewer strip breaks. One of these devices take the form of a measuring roll, which the strip is guided over after it has exited the reduction stage in the mill. The roll is traditionally used in cold rolling applications, and a desire to move to hot rolling introduces demands for research into the thermal balances that develops under operation. This report aims to create an overview into some of the contributions that make up the thermal balance, namely external convection and friction losses in bearings. Other contributions have been investigated by C. Karlsson (Master of Science thesis, Karlstad University, 2018). The heat transfer coefficients obtained for external convection proved to be too small to sustain reasonable temperatures under operation, if no type of cooling apparatus is utilized. Even with external cooling using pressurized air, the convective heat dissipation is too low, due to efficient strip-to-roll conduction. From the modelling performed in this report, friction losses from bearings can be considered as negligible. A model for describing the thermal balances using Newton’s law of cooling was developed, and related to steady state operating conditions by the use of a correction factor. The factor was obtained by comparing the cooling law with the results of a more precise numerical model. The studies in this project elucidate the critical aspects of the thermal balances and provides a basis for further, more detailed modelling.

The growth of atomically flat silver films on Si(111) usually requires a two-step growth, including deposition at low temperature (≈100 K) followed by slowly annealing to room temperature. In addition, flat silver films are usually only obtained on Si(111) for film thicknesses larger than the critical thickness of 6 monolayer. In this work, Ag thin film formation at ambient temperature on Sn/Si(111)-√3×√3 has been investigated experimentally using a combination of scanning tunneling microscopy, scanning tunneling spectroscopy and low-energy electron diffraction. The first buffer layer, probably consisting of both Ag and Sn, formed a partially ordered structure consisting of atomic rows which mainly followed the high-symmetry directions of the underlying Si(111) lattice. From 3 ML coverage, an atomically flat Ag film was formed. Low-energy electron diffraction confirmed that the films grew in the [111]-direction. This shows that atomically flat Ag films as thin as 3 ML can be grown on Sn/Si(111)-√3×√3 by conventional deposition at room temperature. The electronic structures of the films were studied for a range of different coverages by scanning tunneling spectroscopy. The normalized tunneling conductance showed quantum well states in the occupied electronic states, which moved towards the Fermi energy with increasing film thicknesses. 

In this thesis, two MFC based films Carboxymethylated-Microfibrillated Cellulose (MFC) and Enzymatic-MFC were characterized and metalized in order to improve the barrier properties at high relative humidity. Several methods were used for the characterization process, which were Atomic Force Microscopy (AFM), Contact Angle (CA), Energy Dispersive Spectra (EDS), Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Oxygen Transmission Rate (OTR). Physical Vapor Deposition (PVD) system was used for the metalization of film, a thin layer of aluminium with a thickness of 200 nm was deposited on the films. The results revealed that ENZ-MFC exhibit a higher roughness and lower OTR values, compared to CM-MFC. The contact angle values proved that both non-metalized MFC films exhibited a hydrophilic surface with values around 50 degrees. SEM and EDS images showed that both films exhibited surface defects with dimensions in the order of a micrometer.

The best barrier improvement by metalization was achieved for the metalized CM-MFC, where the OTR values were decreased by one order of magnitude after metalization. However, for ENZ-MFC metalization did not improve OTR at high RH. The protective layer was successfully protecting the MFC film as long as the surface roughness of the film was not too high. The limit is between 40 and 140nm (in root mean square roughness values).

Planning algorithms have applications in many fields such as robotics, logistics, and more.Planning for terrain following flights can be to utilize features of the terrain to minimizethe risk of detection. The similar problem of terrain avoidance is applicable to planningthe movement for survey or search vehicles, where low and fixed altitude may be important.Common problems that arise when planning for terrain following flights is that the dynamics ofthe vehicle are difficult to model, the state space is only represented in an approximate mannerand detailed calculations of the subject are computationally expensive. This work presents aplanning algorithm for the vertical component of terrain following flight paths using methods ofenergy, where the path itself is modelled as an elastic band deformed by virtual forces to followthe terrain. Using linear internal equations of motion for the elastic band, the computationalcomplexity can be kept low. Similar ideas have been used for planning algorithms in otherworks, but novel to the method presented here is that complicated limitations to the dynamicsof the vehicle can be treated in an effective manner. This is achieved by an adaptive linearcombination of different models for the internal elastic forces.

To predict fluid properties and interactions is an important task for the industry. It is plagued, however, by being close to impossible to predict analytically. Hence, it is customary to turn to numerical solutions. This in itself comes with many different methods and approaches suitable for different needs. This work focuses on two methods: Tip Vortex Index (TVI) and Diffused Vortex Hydrodynamics (DVH). TVI is a method to predict when a marine propeller will experience cavitation of tip vortices and is based on calculations from a Boundary Element Method (BEM). DVH is a particle method for simulating the circulation of a fluid in two dimensions and three dimensions. The aim is to investigate an implemented TVI model based on MPUF-3A for different marine propeller series, with different sub-designs for a total of 28 unique propellers, and implement the DVH method and test it for 3 different bodies. The results of this thesis show that the implemented TVI model is non-functional for the 28 different propellers, but the DVH method is successfully implemented and able to handle 2 different bodies.

In this thesis, Atomic Force Microscopy (AFM) is used to characterize Micro Fibrillated Cellulose (MFC) produced by two different methods according to their size and shape. For one of these MFC-types, their interaction with the humidity in the atmosphere is investigated and their swelling is calculated. MFC is a relatively new material based on cellulose fibres extracted from wood. This study is performed in co-operation with Stora Enso research centre. Stora Enso is a renewable material company which uses mostly wood based raw materials in their production. The measured swelling is ~ 5 % and depends on the number of elementary fibrils included in the fibre.

In this thesis work several manufacturing methods for graphene is discussed followed by an indepth study of graphene grown by a high temperature sublimation method (sublimation of siliconcarbide). The graphene surfaces studied have been grown by Graphensic AB, both graphenegrown on the Si-face and the C-face of the silicon carbide were studied. Six graphene samplesgrown 4H-SiC substrates were examined for homogeneity and surface morphology as well assome surface roughness parameters using Atomic Force Microscopy (AFM). The graphene wasstudied to get a better understanding of the surfaces and the growth mechanisms to improvemanufacturing parameters while also being informative for graphene sample customers. Anadditional graphene sample grown on 6H-SiC epitaxial layer was also studied to get a betterunderstanding of the sublimation mechanism. If graphene could be manufactured in a cheaprepeatable way the applications are endless and a new era of technology could emerge muchlike the silicon era that began several decades ago. In this thesis work the results are presentedas topography images as well as tables and histograms in the results section. The growth onthe Si-face is found to be well ordered when compared to the C-face which shows signs of alargely complex growth. The graphene on the Si-face lies on top of silicon carbide steps like acarpet with a buer layer interface against the silicon carbide. On the C-face this buer layeris not present but the graphene is deformed by buckling which is suspected to originate fromdierences in thermal properties between the graphene and the C-face. The in uence of AFMsettings for characterization of graphene while using intermittent mode have been evaluated andrecommendations are given. Finally a method for evaluating the homogeneity of the graphenelm is proposed but is in need of further verication.

Topological order is a new field of research involving exotic physics. Among other things it has been suggested as a means for realising fault-tolerant quantum computation. Topological degeneracy, i.e. the ground state degeneracy of a topologically ordered state, is one of the quantities that have been used to characterize such states. Topological order has also been suggested as a possible quantum information storage.

We study two-dimensional lattice models defined on a closed manifold, specifically on a torus, and find that these systems exhibit topological degeneracy proportional to the genus of the manifold on which they are defined. We also find that the addition of lattice dislocations increases the ground state degeneracy, a behaviour that can be interpreted as artificially increasing the genus of the manifold. We derive the fusion and braiding rules of the model, which are then used to calculate the braiding properties of the dislocations themselves. These turn out to resemble non-abelian anyons, a property that is important for the possibility to achieve universal quantum computation. One can also emulate lattice dislocations synthetically, by adding an external field. This makes them more realistic for potential experimental realisations.

Carbon nanotubes (CNTs) have drawn a lot of attention during the last decades due to its promising mechanical and electrical properties. Extensive research regarding the mechanical properties of CNTs has been carried out during the last decades. A lot of effort has been put into developing methods to properly characterize features such as Young’s modulus and the deformation processes of carbon nanotubes. A detailed knowledge of these properties is important for many of the suggested applications of carbon nanotubes.Here we have examined multiwalled carbon nanotubes (MWCNTs) grown by pyrolysis of ferrocene. In some cases the carbon nanotube contained an iron core or traces of iron in the core. The carbon nanotubes ranged from 20 nm to 65 nm in radius and 1000 nm to 4000 nm in length.An atomic force microscope (AFM) was used inside a scanning electron microscope (SEM) for in situ force measurements. The AFM cantilever was used to displace individual carbon nanotubes from their equilibrium positions. The forces used to displace the carbon nanotubes have been plotted against the displacements of the tubes to obtain the characteristic force-displacement curves. From the slope of these curves the spring constants of the carbon nanotubes have been found. Young’s modulus for each tube was derived from the spring constant and the tube dimensions.We found that Young’s modulus ranged from 7 GPa to 340 GPa with no observed dependence on the radius or the length. Previous works suggest that deformation processes such as rippling and buckling will drastically change the spring constant of the tubes when displaced. The maximum values of the applied forces in our measurements were smaller than those needed to push the tubes into the deformation stages. The relatively low values of Young’s modulus indicate that these tubes are rich in defects which dominate their mechanical behaviour.

The Yang-Baxter equation appear in various situations in physics and mathematics. For example it arises as a consistency condition in integrable models. The reflection equation (boundary Yang-Baxter equation) is a generalization of the Yang-Baxter equation to systems with a boundary. A further generalization to systems with defects which admits both reflection and transmission can be made, which results in reflection-transmission Yang-Baxter equations.In this thesis the Yang-Baxter equation and the reflection equation are presented. Representations of the Temperley-Lieb algebra and the blob algebra are used to construct matrices which solve the respective equations. For the reflection-transmission Yang-Baxter equations, steps toward a solution are taken by using a similar approach as for the first two cases, namely by finding an algebra whose representations can be used to construct matrices which solve the equations.