Recently, the more widespread use of three-dimensional (3-D) imaging modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), and ultrasound (US) have generated a massive amount of volumetric data. These have provided an impetus to the development of other applications, in particular telemedicine and teleradiology. In these fields, medical image compression is important since both efficient storage and transmission of data through high-bandwidth digital communication lines are of crucial importance. Despite their advantages, most 3-D medical imaging algorithms are computationally intensive with matrix transformation as the most fundamental operation involved in the transform-based methods. Therefore, there is a real need for high-performance systems, whilst keeping architectures exible to allow for quick upgradeability with real-time applications. Moreover, in order to obtain efficient solutions for large medical volumes data, an efficient implementation of these operations is of significant importance. Reconfigurable hardware, in the form of field programmable gate arrays (FPGAs) has been proposed as viable system building block in the construction of high-performance systems at an economical price. Consequently, FPGAs seem an ideal candidate to harness and exploit their inherent advantages such as massive parallelism capabilities, multimillion gate counts, and special low-power packages. The key achievements of the work presented in this thesis are summarised as follows. Two architectures for 3-D Haar wavelet transform (HWT) have been proposed based on transpose-based computation and partial reconfiguration suitable for 3-D medical imaging applications. These applications require continuous hardware servicing, and as a result dynamic partial reconfiguration (DPR) has been introduced. Comparative study for both non-partial and partial reconfiguration implementation has shown that DPR offers many advantages and leads to a compelling solution for implementing computationally intensive applications such as 3-D medical image compression. Using DPR, several large systems are mapped to small hardware resources, and the area, power consumption as well as maximum frequency are optimised and improved. Moreover, an FPGA-based architecture of the finite Radon transform (FRAT)with three design strategies has been proposed: direct implementation of pseudo-code with a sequential or pipelined description, and block random access memory (BRAM)- based method. An analysis with various medical imaging modalities has been carried out. Results obtained for image de-noising implementation using FRAT exhibits promising results in reducing Gaussian white noise in medical images. In terms of hardware implementation, promising trade-offs on maximum frequency, throughput and area are also achieved. Furthermore, a novel hardware implementation of 3-D medical image compression system with context-based adaptive variable length coding (CAVLC) has been proposed. An evaluation of the 3-D integer transform (IT) and the discrete wavelet transform (DWT) with lifting scheme (LS) for transform blocks reveal that 3-D IT demonstrates better computational complexity than the 3-D DWT, whilst the 3-D DWT with LS exhibits a lossless compression that is significantly useful for medical image compression. Additionally, an architecture of CAVLC that is capable of compressing high-definition (HD) images in real-time without any buffer between the quantiser and the entropy coder is proposed. Through a judicious parallelisation, promising results have been obtained with limited resources. In summary, this research is tackling the issues of massive 3-D medical volumes data that requires compression as well as hardware implementation to accelerate the slowest operations in the system. Results obtained also reveal a significant achievement in terms of the architecture efficiency and applications performance.

All substances above zero kelvin temperature emit fluctuating electromagnetic waves due to the random motions of charge carriers. Controlling the spectral and directional radiative properties of surfaces has wide applications in energy harvesting and thermal management. Artificial metamaterials have attracted much attention in the last decade due to their unprecedented optical and thermal properties beyond those existing in nature. This dissertation aims at tailoring radiative properties at infrared regime and enhancing the near-field radiative heat transfer by employing metamaterials. A comprehensive study is performed to investigate the extraordinary transmission, negative refraction, and tunable perfect absorption of infrared light. A polarizer is designed with an extremely high extinction ratio based on the extraordinary transmission through perforated metallic films. The extraordinary transmission of metallic gratings can be enhanced and tuned if a single layer of graphene is covered on top. Metallic metamaterials are not the unique candidate supporting exotic optical properties. Thin films of doped silicon nanowires can support negative refraction of infrared light due to the presence of hyperbolic dispersion. Long doped-silicon nanowires are found to exhibit broadband tunable perfect absorption. Besides the unique far-field properties, near-field radiative heat transfer can be mediated by metamaterials. Bringing objects with different temperatures close can enhance the radiative heat flux by orders of magnitude beyond the limit set by the Stefan-Boltzmann law. Metamaterials provide ways to make the energy transport more efficient. Very high radiative heat fluxes are shown based on carbon nanotubes, nanowires, and nanoholes using effective medium theory (EMT). The quantitative application condition of EMT is presented for metallodielectric metamaterials. Exact formulations including the scattering theory and Green’s function method are employed to investigate one- and two-dimensional gratings as well as metasurfaces when the period is not sufficiently small. New routes for enhancing near-field radiative energy transport are opened based on proposed hybridization of graphene plasmons with hyperbolic modes, hybridization of graphene plasmons with surface phonon modes, or hyperbolic graphene plasmons with open surface plasmon dispersion relation. Noncontact solid-state refrigeration is theoretically demonstrated to be feasible based on near-field thermal radiation. In addition, the investigation of near-field momentum exchange (Casimir force) between metamaterials is also conducted. Simultaneous enhancement of the near-field energy transport and suppress of the momentum exchange is theoretically achieved. A design based on repulsive Casimir force is proposed to achieve tunable stable levitation. The dissertation helps to understand the fundamental radiative energy transport and momentum exchange of metamaterials, and has significant impacts on practical applications such as design of nanoscale thermal and optical devices, local thermal management, thermal imaging beyond the diffraction limit, and thermophotovoltaic energy harvesting.

This thesis presents theoretical work on armed group activity and empirical work on post-conflict recovery. In chapter two, I develop a general equilibrium model of violence to explain observed variation in coercive practices in conflict zones. Armed groups own land in the resource sector and allocate military resources between conflict and coercion, which assign de facto ownership over land and labour respectively. I find that coercion is higher if labour is scare relative to land, production is labour-intensive, or if one group is dominant relative to others. Furthermore, contrary to other studies, I find that coercion could decreases with price if military power is sufficiently decentralised, since conflict draws resources away from coercion. In chapter three, I evaluate a reconciliation program in post-conflict Sierra Leone. The program provides a forum for villagers to air war-time grievances, and also forges institutions designed to improve conflict resolution and build social capital. I find that respondents who received the intervention are more forgiving and are more charitable in their views of ex-combatants. Furthermore, conflict resolution improved and involvement in village groups and activities increased. However, psychological health---depression, post-traumatic stress disorder and anxiety---deteriorated. This study has direct implications for the design of transitional justice programs, as well as programs that aim to promote institutional change. In chapter four, I experimentally vary foreigner presence across behavioural games conducted in 60 communities in Sierra Leone, and assess its effect on standard measures of generosity. I find that foreigner presence substantially increases player contributions in dictator games, by an average of 19 per cent. Furthermore, the treatment effect is smaller for players who hold positions of authority; and subjects from villages with greater exposure to development aid give substantially less and are more inclined to believe that the behavioural games were conducted to test them for future aid. In chapter five, I use a model of repeated bargaining with one-sided asymmetric information to investigate the difficulties of reaching and sustaining power sharing agreements. I show that asymmetric information can explain the persistence of conflict, since learning slows down when there are future opportunities for bargaining.

The overall objective of this thesis has been to develop accurate computational methods for the diffusion and adsorption of small gases in zeolites. Firstly, the effect of the zeolite framework flexiblity on the single component and binary diffusion of various gases were discussed. Results indicate that for tight fitting molecules the rigid framework approximation can produce order(s) of magnitude difference in diffusivities as compared to the simulations performed with a fully flexible framework. We proposed two simple methods in which the flexible structure of a zeolite is approximated as a set of discrete rigid snapshots. Both methods are orders of magnitude more efficient than the simulations with the fully flexible structure. Secondly, we use a combined classical and quantum chemistry based approach to systematically develop the force fields based on DFT calculations for interactions of simple molecules like CH4, N2, linear alkanes, and linear alkenes in zeolites. We used a higher level of theory known as the DFT/CC method to correct DFT energies that were used in the periodic DFT calculations to develop force fields. Our results show that DFT-derived force fields give good predictions of macroscopic properties like adsorption isotherms in zeolites. The force fields are transferrable across zeolites and hence can be further used to screen materials for different storage and separation applications.

The purpose of the study was to psychometrically evaluate the Revised Janis and Field Scale using the rasch model. The model is a measurement model often used to develop and improving composite measures. Quantitative content analysis was also used in the study. After the two analyses were conducted the problematic items were examined, where an interpretative perspective was applied to try to explain why some questions didn’t seem to work as intended. The other purpose of the study was to examine if emotional and cognitive components need to be treated as separate variables when studying self-esteem. The data collection was administrated at Karlstad University in April of 2014. In total 225 respondents participated in the survey, of whom 140 were women and 85 were men. Based on the rasch model, the instrument did not seem to measure self-esteem in an acceptable manner. There were also major problems with the content of the questions and how they were structured. It is concluded that the instrument should not be used for research purposes. Based on the analyses it was not possible to determine if it’s necessary to distinguish between emotional and cognitive components of self-esteem. It requires more analysis, based on more reliable instruments in the future. / Syftet med studien var att utvärdera mätinstrumentet Revised Janis and Field Scale med hjälp av psykometriska analyser baserat på raschmodellen. Raschmodellen är en mätmodell som används inom olika discipliner vid utveckling och granskning av mätinstrument. Därutöver genomfördes här även en kvantitativ innehållsanalys. När de två analyserna var genomförda granskades problematiska frågor, där ett tolkningsperspektiv anlades för att försöka förklara varför vissa frågor inte verkade fungera som avsett. Avsikten med studien var även att undersöka om emotionella och kognitiva beståndsdelar bör hanteras som separata variabler. Datainsamlingen ägde rum vid Karlstads universitet under april månad 2014. Totalt deltog 225 respondenter i undersökningen, 140 kvinnor respektive 85 män. Baserat på raschanalysen verkar inte instrumentet mäta självkänsla på ett godtagbart sätt. Därutöver finns problem med de ämnen som frågorna behandlar och hur frågorna samt svarsalternativen är formulerade. Bedömningen gjordes baserat på analyserna att instrumentet inte bör användas i vetenskapliga sammanhang. Avslutningsvis var det inte möjligt att bekräfta om det är nödvändigt att särskilja mellan emotionella och kognitiva beståndsdelar ur självkänslan utifrån de analyser som genomförts här. Det krävs att fler analyser genomförs i framtiden och att dessa bygger på mer stabila mätinstrument för att uppnå det syftet. / Self-esteem, The Self, Revised Janis and Field Scale, Rasch analysis

International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper briefly reviews past techniques for measuring FM deviation and discusses the limitations of past technology. Graphs of the Bessel functions are presented in terms of decibels (dB), offering a better method of measurement when used with a modern spectrum analyzer.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

By formulating the six dimensional (0,2) superconformal field theory X[j] on a Riemann surface decorated with certain codimension two defects, a multitude of four dimensional N=2 supersymmetric field theories can be constructed. In this dissertation, various aspects of this construction are investigated in detail for j=A,D,E. This includes, in particular, an exposition of the various partial descriptions of the codimension two defects that become available under dimensional reductions and the relationships between them. Also investigated is a particular observable of this class of four dimensional theories, namely the partition function on the four sphere and its relationship to correlation functions in a class of two dimensional non-rational conformal field theories called Toda theories. It is pointed out that the scale factor that captures the Euler anomaly of the four dimensional theory has an interpretation in the two dimensional language, thereby adding one of the basic observables of the 4d theory to the 4d/2d dictionary. / text