<p>Since 2002, the Division for Electricity at Uppsala University has been running the Lysekil project. The project is an attempt to construct and evaluate a technology for extracting electrical energy from the motion of ocean waves. The idea is to let this up-and-down motion drive a linear generator. A buoy moves thus in the waves, and is connected through a line to the generator at the sea floor. Three such wave energy converters, L1, L2, and L3, and a marine substation have been deployed in the ocean southwest of Lysekil on the Swedish west coast, at the Lysekil research site. Measuring equipment has also been deployed, together with a number of buoys for studying environmental impact. A measuring station has been installed on the nearby island of Hermanö, and an observation tower has been built on the islet of Klammerskär, south of the research site. This licentiate thesis describes the author's work on studying wave buoy motion and is based on five scientific papers, covering mainly two areas. Firstly, changes in water levels, and thereby changes in the equilibrium point for the buoy and generator, have been related to the ability of L1 to absorb energy. The results indicate that there is a correlation between water levels and energy absorption for L1 for the studied time period. When the water level deviates from average, the absorption values decrease. This is not unexpected, since the linear generator has a finite stroke. The effect is however noticeable primarily for water level deviations of more than 25 cm, and is only visible for those cases where either wave height or water level deviation is large. Secondly, the above mentioned observation tower has been designed and built. The tower is equipped with a network camera covering the research site, a wireless communication system and an energy system. The first acquired images of the buoy connected to L1, taken during the summer of 2008, have been analyzed, and buoy motion data has been extracted. The observation system has worked well, and the data on buoy motion (vertical motion in the range of +/-0.5 m correlates fairly well to measurements of significant wave height for the period (Hm0=0.82 m). A comparison with voltage data from the generator also indicates that the system has captured the dominating buoy motion. However, the system suffers from poor temporal resolution (about one image per second), and has not yet been synchronized with the other measurement systems at the site. Addressing these two problems is of high priority in the future.</p>

<p>Free-flowing water currents such as tides and unregulated water courses could contribute to world electricity production given the emergence of robust technical solutions for extracting the energy. At Uppsala University, a concept for converting water currents to electricity using a vertical axis turbine with fixed blade pitch and a direct drive permanentmagnet generator is studied. A system approach is desired, and in this thesis, a first analysis of two system components, the generator and the turbine, is presented. This thesis also deals with some issues concerning the design and construction of a low speed generator for this application. An experimental generator for verification of simulations has been designed and constructed. For the electromagnetic design, a FEM simulation tool has been used. The construction work has given valuable practical experience concerning for example handling permanent magnets and winding the generator with cable. Simulations and measurements of the experimental generator have been carried out for different speeds and loads. The generator can operate at the speeds and loads corresponding to maximum power capture for different turbines for water current velocities between approximately 0.5 and 2.5 m/s. At higher water current velocities the turbines may need to be run at a tip speed ratio that gives a lower power capture in order to limit the electrical currents in the generator, cavitation of the blades, or mechanical loads. Comparisons of measurements and simulations show an agreement. The FEM simulation tool can be used to simulate and design electrical machines with a low electrical frequency, i.e. 2–16 Hz.</p>

No description available.

<p>Hydrokinetic energy, referring to the energy contained in moving water, is a renewable energy source that has gained much attention the past years. The energy is found in all moving water masses, but is only economical to convert for water masses moving with high velocity, i.e. likely around 1 m/s and above. This energy can for example be found in tidal, ocean and river currents which flow through narrow straits and channels. Along the west coast of Norway, there are many sites where kinetic energy conversion would be possible due to the strong current present. The driving force behind the currents is the tidal wave that progresses northward along the coast and increases in strength. The models that so far have been used for estimating the resource in Norway have been shown to be uncertain since they do not account for the fact that the velocities and the water levels are altered when energy is extracted. These effects can be simulated with numerical models. A channel in the Dal river, the Söderfors channel, is situated downstream a hydropower plant and was simulated with the numerical model MIKE. The water level alteration due to turbines was simulated. It was shown to be a lot less than the water level alteration caused by the level change in the downstream lake. Velocity profiles measured at several different locations were used to estimate how the power coefficient was changed. Four turbine configurations were studied and it was shown that changes in the power coefficient were prominent only for a vertical shear profile with a strong gradient. At the Division of Electricity, studies have been conducted on how to convert hydrokinetic energy to electricity since 2003. The main idea has been to use a system that limits the need for maintenance. The concept studied is a vertical axis turbine directly coupled to a permanent magnet generator. The Söderfors channel has, due to aspects such as the flow properties and velocity, been chosen as a site for an experimental station.</p>

<p>Diamond is a promising material for high-power, high-frequency and hightemperatureelectronics applications, where its outstanding physical propertiescan be fully exploited. It exhibits an extremely high energy gap, veryhigh carrier mobilities, high breakdown field strength, and the highest thermalconductivity of any wide bandgap material. It could therefore producethe fastest switching, the highest power density, and the most efficient electronicdevices obtainable, with applications in the RF power, automotive andaerospace industries. Lightweight diamond devices, capable of high temperatureoperation in harsh environments, could also be used in radiationdetectors and particle physics applications where no other semiconductordevices would survive.The high defect and impurity concentration in natural diamond or polycrystallinehigh-pressure-high-temperature (HPHT) diamond substrates hasmade it difficult to establish reliable results when studying the electronicproperties of diamond. However, recent progress in the growth of high puritySingle-Crystal Chemical Vapor Deposited Diamond (SC-CVD) has openedthe perspective of applications under such extreme conditions based on thistype of artificial diamond.Despite the improvements, there are still many questions which must beanswered. This work will focus on electrical characterization of (SC-CVD)diamond by different measurements techniques such as internal photoemission,I-V, C-V, Hall and in particular, time-of-flight (TOF) carrier driftvelocity measurements. With the mentioned techniques, some importantproperties of diamond such as drift mobilities, lateral carrier transit velocities,compensation ratio and Schottky barrier heights have been investigated.Low compensation ratios (ND/NA) < 10-4 have been achieved in boron-dopeddiamond and a drift mobility of about 860 cm2 / V for the hole transit nearthe surface in a lateral TOF configuration could be measured.</p>

<p>Min målsättning med denna uppsats har varit att forska kring hur kortvågsradion kan öka rörligheten på svenska förband i utlandsstyrkan. Inledningsvis har jag definerat vad jag menar med manöverkrigsföring, uppdragstaktik, de sex grundläggande förmågorna och radio. Jag har intervjuat individer som varit på enheter som rört sig i terrängen i Afghanistan och Kosovo. Jag har sedan diskuterat kring hur man kan öka rörligeheten genom att använd sig av uppdragstaktik och kortvågsradion. Jag har jämfört ledningsätt och radioanvändande mellan Afghanistan och Kosovo och dragit slutsatser från detta.</p><p>En av slutsatserna som har dragits ur uppsatsen är att det är räckvidden som möjliggör en högre rörlighet genom att enheterna inte blir styrda till att hålla sig inom t.ex. en RAP-täckningskarta utan ger dem större möjlighet att själva välja framryckningsväg och möjliggöra att uppdragstaktik[1] kan utnyttjas på ett effektivare sätt.</p><p>Denna slutsats beskriver hur rörlighet och uppdragstaktik blir effektivare genom att använda sig av kortvågsradion.</p><p>Jag anser att kortvågsradion är ett radiosystem som försvarsmakten böra behålla och utveckla. Det som bör utvecklas är antenner och radio utrustningen som har tagit upp i uppsatsen. Förslag på förbättringar är att antennerna utvecklas så att man kan ha en antenn för alla frekvensområden så man inte behöver stanna fordonet och upprätta en deltaantenn[2] för att kunna sända på den lämpligaste frekvensen vid tillfället. Att det finns en individ vid campen som har som uppgift att uppdaterade frekvenspaketen varje vecka eftersom frekvenserna är väderberoende, för att mögligöra att radioförbindelsen blir så bra som mögligt. Radioapparaterna borde byggas med dagen elektronikkomponenter vilket skulle medföra mindre radioapparater, bättre batteritid och en mer lättmanövrerad radioapparat. </p><p>Jag kommer att avsluta med ett citat ur doktrin för markoperationer som jag anser styrker min uppsats:</p><p><em>”De ledningssystem som försvarsmakten använder ska medge en så stor flexibilitet som mögligt i valet av medel och metoder. Detta innebär att det bör finnas en inbyggd förmåga som möjliggör ledning från såväl en framskjuten plats inom ett operationsområde som från en stabsplats<strong>[3]</strong>”.</em></p><p> </p>

The theme of this dissertation is the design of IT artefactsfor increased well-being in the home. The goal has been toprovide a better understanding of the coupling between designand health, and to give examples of how to design for increasedwell-being. The context for the investigation has been thehome, and various research initiatives in smart homes andIT-supported care. We create our reality in the form of material structuressuch as buildings, products, workplaces and homes. Theseartefacts are a reflection of ourselves, we have created themand we understand ourselves through them. Together withimmaterial artefacts like political systems, educationalsystems and healthcare, they constitute our society. Thetotality of these material and immaterial artefacts forms theconditions of our everyday life. This investigation points at anew way to look at artefacts as social actors in an interactiveworld. In this perspective, use becomes a dialogue andcooperation with the artefact. Design work becomes a carefulcreative practice in which the focus is the interplay betweenthe artefact and its social environment. Stress and ill-healthis an indication that there is an unbalance in the interplay.Well-being on the other hand means that there is a balancebetween the artificial world and the individual. Designpractitioners, and others that create our world, have animportant task in designing new artefacts that do not reproduceobsolete or dysfunctional behaviour. Inspired by coping theories, a salutogenic approach todesign aims at identifying and strengthening the aspects ofartefacts that help us handle adversities. This means to createartefacts that form a world, which is comprehensible,manageable and meaningful. People that live in environmentswhere they cannot influence decisions, with high demands andlow control, are likely to become ill. But people that haveenvironments, in which they receive feedback, support and cancontrol their own situation stay well. With new, complextechnology such as ubiquitous computing, it becomes even moreimportant to support recognition and routines. And it becomesessential in domestic use and in IT-support for the disabledand elderly. The empirical work reported here consists of four casestudies related to IT artefacts for well-being. The casestudies include field studies, critical analysis, designconcepts, prototype building and evaluation. Based on thefindings in these studies, four considerations for design ofinteractive systems for the home are suggested: design forunderstanding, for detecting and managing of errors, fordisabling and for alternative coping. Finally it is suggested that if research is to concernitself not only with evaluations and general laws, but alsowith ideas and practical examples of a better future life–then design knowledge becomes an essential element inresearch. In this endeavour we need more cooperation betweenpractitioners from the social and technical sciences, thehumanities and design. / QC 20100618

This thesis introduces a new signal transform, called polynomial expansion, and based on this develops novel methods for estimation of orientation and motion. The methods are designed exclusively in the spatial domain and can be used for signals of any dimensionality. Two important concepts in the use of the spatial domain for signal processing is projections into subspaces, e.g. the subspace of second degree polynomials, and representations by frames, e.g. wavelets. It is shown how these concepts can be unified in a least squares framework for representation of nite dimensional vectors by bases, frames, subspace bases, and subspace frames. This framework is used to give a new derivation of normalized convolution, a method for signal analysis that takes uncertainty in signal values into account and also allows for spatial localization of the analysis functions. Polynomial expansion is a transformation which at each point transforms the signal into a set of expansion coefficients with respect to a polynomial local signal model. The expansion coefficients are computed using normalized convolution. As a consequence polynomial expansion inherits the mechanism for handling uncertain signals and the spatial localization feature allows good control of the properties of the transform. It is shown how polynomial expansion can be computed very efficiently. As an application of polynomial expansion, a novel method for estimation of orientation tensors is developed. A new concept for orientation representation, orientation functionals, is introduced and it is shown that orientation tensors can be considered a special case of this representation. By evaluation on a test sequence it is demonstrated that the method performs excellently. Considering an image sequence as a spatiotemporal volume, velocity can be estimated from the orientations present in the volume. Two novel methods for velocity estimation are presented, with the common idea to combine the orientation tensors over some region for estimation of the velocity field according to a parametric motion model, e.g. affine motion. The first method involves a simultaneous segmentation and velocity estimation algorithm to obtain appropriate regions. The second method is designed for computational efficiency and uses local neighborhoods instead of trying to obtain regions with coherent motion. By evaluation on the Yosemite sequence, it is shown that both methods give substantially more accurate results than previously published methods. Another application of polynomial expansion is a novel displacement estimation algorithm, i.e. an algorithm which estimates motion from only two consecutive frames rather than from a whole spatiotemporal volume. This approach is necessary when the motion is not temporally coherent, e.g. because the camera is affected by vibrations. It is shown how moving objects can robustly be detected in such image sequences by using the plane+parallax approach to separate out the background motion. To demonstrate the power of being able to handle uncertain signals it is shown  how normalized convolution and polynomial expansion can be computed for interlacedvideo signals. Together with the displacement estimation algorithm this gives a method to estimate motion from a single interlaced frame.

The art of medical computed tomography is constantly evolving and the last years have seen new ground breaking systems with multi-row detectors. These tomographs are able to increase both scanning speed and image quality compared to the single-row systems more commonly found in hospitals today. This thesis deals with three-dimensional image reconstruction algorithms to be used in future generations of tomographs with even more detector rows than found in currentmultirow systems. The first practical algorithm for three-dimensional reconstruction from conebeamprojections acquired from a circular source trajectory is the FDKmethod. We present a novel version of this algorithm that produces images of higher quality. We also formulate a version of the FDK method that performs the backprojection in O(N3 logN) steps instead of the O(N4) steps traditionally required. An efficient way to acquire volumetric patient data is to use a helical source trajectory together with a multi-row detector. We present an overview of existing reconstruction algorithms for this geometry. We also present a new family of algorithms, the PI methods, which seem to surpass other proposals in simplicity while delivering images of high quality. The detector used in the PI methods is limited to a window that exactly fits the cylindrical section between two consecutive turns of the helical source path. A rebinning to oblique parallel beams yields a geometry with many attractive properties. The key property behind the simplicity of the PI methods is that each object point to be reconstructed is illuminated by the source during a rotation of exactly half a turn. This allows for fast and simple reconstruction.

The thesis describes novel methods for image motion computation and template matching. A multiscale algorithm for energy-based estimation and representation of local spatiotemporal structure by second order symmetric tensors is presented. An efficient spatiotemporal implementation of a signalmodellingmethod called normalized convolution is described. This provides a means to handle signals with varying degree of reliability. As an application of the above results, a smooth pursuit motion tracking algorithm that uses observations of both targetmotion and position for camera head control and motion prediction is described. The target is detected using a novel motion field segmentation algorithm which assumes that the motion fields of the target and its immediate vicinity, at least occasionally, each can be modelled by a single parameterized motion model. A method to eliminate camera-induced background motion in the case of a pan/tilt rotating camera is suggested. In a second application, a high-precision image motion estimation algorithm performing clustering in motion parameter space is developed. The algorithm, which can handle multiple motions by simultaneous motion parameter estimation and image segmentation, iteratively maximizes the posterior probability of the motion parameter set given the observed local spatiotemporal structure tensor field. The probabilistic formulation provides a natural way to incorporate additional prior information about the segmentation of the scene into the objective function. A simple homotopy continuation method (embedding algorithm) is used to increase the likelihood of convergence to a nearoptimal solution. The final part of the thesis is concerned with tracking of (partially) occluded targets. An algorithm for target tracking in head-up display sequences is presented. The method generalizes cross-correlation coefficient matching by introducing a signal confidencebased distance metric. To handle target shape changes, a method for template mask shape-adaptation based on geometric transformation parameter optimisation is introduced. The presence of occluding objects makes local structure descriptors (e.g., the gradient) unreliable, which means that only pixelwise comparisons of target and template can be made, unless the local structure operators are modified to take into account the varying signal certainty. Normalized convolution provides the means for such a modification. This is demonstrated in a section on phase-based target tracking, which also contains a presentation of a generic method for tracking of occluded targets by combining normalized convolution with iterative reweighting.