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The thesis comprises an introductory chapter and four research papers. The introductory chapter provides a brief overview of recent economic growth performance in Africa, places the individual papers into a coherent context, summarizes the main findings, and discusses their relevance for economic policy. The first paper, The Role of Capital Accumulation, Adjustment and Structural Change for Take-
It is commonly believed that we live in a culture that is increasingly permeated by visual images. One category of images that we encounter everyday in different media, and that constitutes a large and growing part of media content, is advertisements. Advertisements also have a specific purpose and the images represent, make meaning of, and convey sentiments about phenomena. In this dissertation,
This doctoral thesis treats three issues in control engineering related to relay feedback and multivariable control systems. Linear systems with relay feedback is the first topic. Such systems are shown to exhibit several interesting behaviors. It is proved that there exist multiple fast relay switches if and only if the sign of the first non-vanishing Markov parameter of the linear system is pos
A major aim initially was to create a forum for reflective dialogue on the preschool professions and how it is experienced on a daily basis, so as to be able to investigate how members of the preschool staff construct their professional subject. The following are major questions that were posed: How do preschool staff members talk about themselves, their profession and their work? In what way does
The objective of this thesis is to study the application of ventilation in schools buildings. A number of studies of the application of different forms of ventilation are presented. The main part of the thesis focuses on window opening in a classroom. Analytical models for calculation of the air change caused by window airing are proposed. The models are intended to be a tool for designers and occ
Sierra Leone is a small country with rich mineral resources such as diamonds, bauxite, gold and iron ore. Other resources include fishing, forestry and fertile agricultural land, which enable people to farm without any sophisticated methods of mechanization. Nevertheless, with all its wealth in resources, the country is relatively poor and is one of the least developed countries in the Sub-Saharan
The modeling work developed in this thesis can be divided in two main areas of investigations: autoignition related to spark ignition engine and combustion and emissions formation in relation to diesel engines. A first version of a detailed kinetics engine simulation program, extended to handle full cycle calculations, was employed in order to demonstrate the strong effect that nitric oxide from
Diesel engine developers are facing major challenges when meeting future demands on NOx and particulate emissions. The exhausts after treatment systems are rapidly improving and the technologies available in a few years will be capable of cutting emission levels close to the demanded levels. However, in order to reach the low emissions required in a long-lasting, cost effective way, the potential
The effect of duration of ischaemia on final infarct size is well established in animal studies, but not fully evaluated in humans. Delayed contrast-enhanced magnetic resonance imaging (DE-MRI) can be used to distinguish between viable and non-viable myocardium and thus to quantify infarct size. We therefore used DE-MRI to investigate how duration of ischaemia affects final infarct size normalized
This thesis deals with models of flat plate collectors, transparent insulation and efficiency factors. An equation for the energy output from a glazed flat plate collector is derived by modelling the collector efficiency factor, F´ as the sum of a constant and a temperature dependent part. An alternative way of testing a flat plate collector, based on this model, is suggested. A complete set of a
The performance of cyclones used in occupational hygiene for sampling respirable dust was studied. Test methods for experimental determination of cyclone penetration have been designed and validated. The penetration curve for a sampling cyclone presently used in Europe was measured. The sampler's performance relative to three sampling conventions for respirable dust was determined. The cyclone was
With the increased sophistication of medical implants, there is a growing need for flexible high-speed communication with the implant from outside the body. Today the communication is done by an inductive link between the implant and an external coil at a low carrier frequency. Extended range and communication speed are possible to achieve by increasing the carrier frequency and the bandwidth. One
This thesis is concerned with the propagation of transient electromagnetic waves in nonlinear media. It consists of a General Introduction and five scientific papers. The General Introduction gives a broad overview of nonlinear electromagnetic phenomena. The emphasis is on the representation of the constitutive functional modeling the material's response to electromagnetic excitation, and the met
This thesis has the main focus on ways to improve the blood perfusion estimate, as obtained from a continuous wave Doppler system. Earlier studies have shown large temporal variations in the detected perfusion estimate, due to speckle. Here, a theoretical model to predict frequency dependent characteristics of speckle in continuous wave ultrasound is presented. The model predicts the frequency shi
The processes that govern the formation, existence and consumption of ions in gases have been studied both experimentally and theoretically. The aim of the work is targeted at increasing the understanding of these phenomena in the working gases inside an engine. Both the cause and the application of ionized gases inside the cylinder of a spark ignited (SI) engine has been studied. The spark disch
In this thesis, a probabilistic framework is presented and used for analysis of the throughput of interfering packet-based radio networks, referred to as packet radio networks (PRNs). Previous research on the performance of PRNs covers a wide variety of systems and aspects in varying levels of detail. However, the work presented in the literature has mostly been limited to fixed packet lengths. Th
This thesis is about voice imitations, more specifically impersonation. Questions are raised about the uniqueness of a person’s voice and speech behaviour and if it is possible to get close to another speaker’s voice and speech. Four main research questions are investigated in different studies. The studies focus mainly on how close the imitation is to the target speaker, and addresses to a lesser
In the business-to-business (B2B) setting much attention has been given to how e-business tools can be used to assist firms in purchasing. Considering the increasing pressure on suppliers to use B2B e-business, this thesis turns its attention to the supplier situation by taking a closer look at how collaborative uses of B2B e-business are of value to suppliers. This book differs from much of the
Molecular recognition and interaction is fundamental for the function of biological systems. The properties of the interacting biomolecules dictate the type of forces involved and the strength and dynamics of the interaction. Many interactions are very strong whereas others exhibit weak affinity. Typically, weak interactions work in concert to trigger a biological response. The advantage with thi
The study is based on data collected at the LEP II accelerator during the second period of the Large Electron-Positron collider operations (1996-2000). During that time the DELPHI (DEtector with Lepton, Photon and Hadron Identification) experiment collected about 90 Gb of data on tape corresponding to 687-691 pb-1 of luminosity. The data obtained by the VSAT (Very Small Angle Tagger) e
