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Wave energy is one of the possible solutions for meeting the future energy demand in a clean and sustainable way. Extracting large amounts of energy, a wave energy device would be subjected to extreme and fatigue loads from the waves. Designing such a device, a trade off needs to be done between making a device that is strong enough to withstand the loads and on the same time not too heavy making it inefficient and too costly. Having good estimations of extreme and fatigue loads are therefore critical when designing an efficient wave energy device. This thesis has aimed to create a tool that can be used between the already existing hydrodynamic and solid mechanic models available at CorPower Oceean. The goal has been that the tool shall extract the extreme and fatigue loads from the hydrodynamic model and format them in a way so that they can be used in the solid mechanical model. Four different tools have been created and compared for calculating fatigue using amplitude and spectral methods, where the amplitude methods also are able to estimate extreme loads. The fatigue tools have been evaluated against each other in a simple example showing that the estimated accumulated fatigue damage can be decreased by using several variables. An application of the tools has been done on a critical sub system of the wave energy device developed by CorPower Ocean. Where in this application critical points against extreme loading and fatigue have been localized. A new design has been suggested based on the strength analysis from the first one. Increasing the number of variables and using the tools developed in this thesis can significantly improve the fatigue damage estimations of the system. What fatigue method to use depends on the details for each case.

Significant effort has recently been directed towards the development of numerically efficient iterative techniques for the solution of boundary integral equation formulations of time harmonic scattering problems. The primary result of this effort has been the development of several advanced numerical techniques which enable the dense matrix-vector products associated with the iterative solution of boundary integral equations to be rapidly computed. However, an important aspect of this problem which has yet to be adequately addressed is the development of rapidly convergent iterative techniques to complement the relatively more mature numerical algorithms which expedite the matrix-vector product operation. To this end, a class of efficient iterative methods for boundary integral equation formulations of two-dimensional scattering problems is presented. This development is based on an attempt to approximately factor (i.e., renormalize) the boundary integral formulation of an arbitrary scattering problem into a product of one-way wave operators and a corresponding coupling operator which accounts for the interactions between oppositely propagating waves on the surface of the scatterer. The original boundary integral formulation of the scattering problem defines the coupling between individual equivalent sources on the surface of the scatterer. The renormalized version of this equation defines the coupling between the forward and backward propagating fields obtained by re-summing the individual equivalent sources present in the original boundary integral formulation of the scattering problem. An important feature of this class of rapidly convergent iterative techniques is that they are based on an attempt to incorporate the important physical aspects of the scattering problem into the iterative procedure. This leads to rapidly convergent iterative series for a number of two-dimensional scattering problems. The iterative series obtained using this renormalization procedure are much more rapidly convergent than the series obtained using Krylov subspace techniques. In fact, for several of the geometries considered the number of iterations required to achieve a specified residual error is independent of the size of the scatterer. This desirable property of the iterative methods presented here is not shared by other iterative schemes for wave scattering problems. Moreover, because the approach used to develop these iterative series depends only on the assumption that the total field can be approximately represented by a summation of independent and oppositely directed waves (and not on the presence of special geometries, etc.), the proposed iterative methods are very general and are thus applicable to a large number of complex scattering problems. / Ph. D.

Given the current obesity epidemic in tandem with the aging US population, it is imperative to identify methods for reducing cardiovascular disease (CVD) risk that will be efficacious for both sexes. Arterial stiffness (AS) is an independent risk factor for a first cardiovascular event that increases with advancing age and obesity. Previous studies have found that modest weight loss (WL) of 5 to 10 percent successfully reduces AS and other risk factors for CVD. However, it remains unclear whether WL via caloric restriction reduces AS similarly among sexes. We tested the hypothesis that WL via caloric restriction would reduce AS more in men than women because men accumulate more abdominal visceral fat (VF) and lose more with WL compared with women of similar age and adiposity. To test our hypothesis AS was assessed from measurements of pulse wave velocity and ultrasonography of the carotid artery (Ã -SI). Total body and VF were measured using dual energy x-ray absorptiometry and computed tomography scans, respectively. Subjects underwent a 12-week WL intervention. No baseline differences in AS were observed between sexes. However, men were heavier and demonstrated higher levels of VF while women were fatter and had higher levels of abdominal subcutaneous fat. Contrary to our hypothesis both sexes experienced similar decreases in AS with WL despite greater reductions in VF in men. Our findings suggest that VF loss is not the primary mechanism mediating reductions in AS with WL. Future studies are needed to determine the mechanisms of arterial destiffening with WL. / Master of Science

A new wave-kinetic numerical method for the propagation of optical waves in weakly inhomogeneous media is discussed, and it is applied to several canonical problems: the propagation of beam and plane waves through a weak 3-D ( or 2-D ) Gaussian eddy. The numerical results are also compared to those from a Monte-Carlo simulation and the first Born approximation. Within the validity of the Liouville approximation, the Wigner distribution function ( WDF ) is conserved along the conventional ray trajectories, and, thus, by discretizing the input WDF with Gaussian beamlets, we can represent the output WDF as a sum of Gaussians, from which irradiance can be obtained by analytical integration of each Gaussian with respect to wavevector. Although each Gaussian beamlet propagates along a geometrical optics ray trajectory, it can correctly describe diffraction effects, and the propagation of optical waves through caustics or ray crossings. The numerical results agree well with either the Monte-Carlo method or the first Born approximation in regions where one or both of these are expected to be valid. / M.S.

The Master’s thesis explains API and features of Google Wave technology, which was designed for flexible real-time collaboration of defined participants. The project aim was description of Google Wave basic elements and creation of sample Wave extensions, demonstrating capabilities of the communication protocol. The first extension (robot) was developed using client libraries in Java. The second extension (gadget) shows another approach of Google Wave extensions, based on XML, HTML, CSS and JavaScript.

In this project, the wave energy converter (WEC) designed at Seabased AB and Uppsala University was modelled in the program MATLAB. In order to increase the average output power, the WEC should be controlled. Therefore, the simulation tool was used to investigate damping strategies where the damping coefficient was changed at different times of the wave period. The tests showed that a suitable damping strategy, matched to the sea state at the specific location of the site and the overall WEC design, increases the average output power, as well as may protect the WEC from damages. This can lead to a more sustainable WEC system, which may contribute to the increasing demand of renewable energy solutions.