Low-density parity-check (LDPC) codes are linear error correcting codes which are capable of performing near channel capacity. Furthermore, they admit efficient decoding algorithms that provide near optimum performance. Their main disadvantage is that most LDPC codes have relatively complex encoders. In this thesis, we begin by giving a detailed discussion of the sum-product decoding algorithm, we then study the performance of LDPC codes on the binary erasure channel under sum-product decoding to obtain criteria for the design of codes that allow reliable transmission at rates arbitrarily close to channel capacity. Using these criteria we show how such codes are designed. We then present experimental results and compare them with theoretical predictions. Finally, we provide an overview of several approaches to solving the complex encoder problem.

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Master of Science / Department of Agricultural Economics / Andrew Barkley / This study examines the effect of extreme climatic conditions (drought, flood, and bushfires) on the livelihood of households in the Bawku West district of Ghana. The research identified the mechanisms with which households cope in such situations, and analyzed factors influencing the adoption of coping strategies for flood, coping strategies for drought, and coping strategies for bushfires. Data for the study were collected in selected villages across the district in the aftermath of the 2007/2008 extreme climatic events (a prolonged drought period followed by an erratic rainfall). A binary logit regression (BLR) model was then specified to estimate factors that influence the adoption of a given coping mechanisms. Results from the BLR model indicate that literacy level, membership with an FBO, household income, and location of households had positive and significant impacts on adaptation to drought. Similarly, source of seeds for planting, membership with an FBO, household income, and farm size had positive significant influence on adaptation to flood. Adaption to bushfire was positively influenced by radio ownership, seed source and income. The main effect of these climatic extreme events on households included destruction of crops, livestock and buildings; food and water shortage; poor yield or harvest and limited fields for livestock grazing. Therefore, government policies should be geared towards creating revenue generating channels and in strengthening institutions that provide access to farm credit, readily available improve seeds and extension. Additionally, policies that expedite information dissemination through radio and other public media will enhance households’ adaptive capacity.

Master of Science / Department of Civil Engineering / Sunanda Dissanayake / In order to improve safety of the overall surface transportation system, each of the critical areas needs to be addressed separately with more focused attention. Statistics clearly show that large-truck crashes contribute significantly to an increased percentage of high-severity crashes. It is therefore important for the highway safety community to identify characteristics and contributory causes related to large-truck crashes. During the first phase of this study, fatal crash data from the Fatality Analysis Reporting System (FARS) database were studied to achieve that objective. In this second phase, truck-crashes of all severity levels were analyzed with the intention of understanding characteristics and contributory causes, and identifying factors contributing to increased severity of truck-crashes, which could not be achieved by analyzing fatal crashes alone. Various statistical methodologies such as cross-classification analysis and severity models were developed using Kansas crash data. Various driver-, road-, environment- and vehicle- related characteristics were identified and contributory causes were analyzed. From the cross-classification analysis, severity of truck-crashes was found to be related with variables such as road surface (type, character and condition), accident class, collision type, driver- and environment-related contributory causes, traffic-control type, truck-maneuver, crash location, speed limit, light and weather conditions, time of day, functional class, lane class, and Average Annual Daily Traffic (AADT). Other variables such as age of truck driver, day of the week, gender of truck-driver, pedestrian- and truck-related contributory causes were found to have no relationship with crash severity of large trucks. Furthermore, driver-related contributory causes were found to be more common than any other type of contributory cause for the occurrence of truck-crashes. Failing to give time and attention, being too fast for existing conditions, and failing to yield right of way were the most dominant truck-driver-related contributory causes, among many others. Through the severity modeling, factors such as truck-driver-related contributory cause, accident class, manner of collision, truck-driver under the influence of alcohol, truck maneuver, traffic control device, surface condition, truck-driver being too fast for existing conditions, truck-driver being trapped, damage to the truck, light conditions, etc. were found to be significantly related with increased severity of truck-crashes. Truck-driver being trapped had the highest odds of contributing to a more severe crash with a value of 82.81 followed by the collision resulting in damage to the truck, which had 3.05 times higher odds of increasing the severity of truck-crashes. Truck-driver under the influence of alcohol had 2.66 times higher odds of contributing to a more severe crash. Besides traditional practices like providing adequate traffic signs, ensuring proper lane markings, provision of rumble strips and elevated medians, use of technology to develop and implement intelligent countermeasures were recommended. These include Automated Truck Rollover Warning System to mitigate truck-crashes involving rollovers, Lane Drift Warning Systems (LDWS) to prevent run-off-road collisions, Speed Limiters (SLs) to control the speed of the truck, connecting vehicle technologies like Vehicle-to-Vehicle (V2V) integration system to prevent head-on collisions etc., among many others. Proper development and implementation of these countermeasures in a cost effective manner will help mitigate the number and severity of truck-crashes, thereby improving the overall safety of the transportation system.

Functional decomposition aims at finding efficient representations for Boolean functions. It is used in many applications, including multi-level logic synthesis, formal verification, and testing. This dissertation presents novel heuristic algorithms for functional decomposition. These algorithms take advantage of suitable representations of the Boolean functions in order to be efficient. The first two algorithms compute simple-disjoint and disjoint-support decompositions. They are based on representing the target function by a Reduced Ordered Binary Decision Diagram (BDD). Unlike other BDD-based algorithms, the presented ones can deal with larger target functions and produce more decompositions without requiring expensive manipulations of the representation, particularly BDD reordering. The third algorithm also finds disjoint-support decompositions, but it is based on a technique which integrates circuit graph analysis and BDD-based decomposition. The combination of the two approaches results in an algorithm which is more robust than a purely BDD-based one, and that improves both the quality of the results and the running time. The fourth algorithm uses circuit graph analysis to obtain non-disjoint decompositions. We show that the problem of computing non-disjoint decompositions can be reduced to the problem of computing multiple-vertex dominators. We also prove that multiple-vertex dominators can be found in polynomial time. This result is important because there is no known polynomial time algorithm for computing all non-disjoint decompositions of a Boolean function. The fifth algorithm provides an efficient means to decompose a function at the circuit graph level, by using information derived from a BDD representation. This is done without the expensive circuit re-synthesis normally associated with BDD-based decomposition approaches. Finally we present two publications that resulted from the many detours we have taken along the winding path of our research.

<div><p>Modern mobile devices have numerous ephemeral tasks. These tasks are driven by background activities, such as push notifications and sensor readings. In order to execute these tasks, the whole platform has to periodically wake up beforehand, and go to sleep afterwards. During this process, the OS kernel operates on power state of various IO devices, which has been identified as the bottleneck for energy efficiency. To this end, we want to offload this kernel phase to a more energy efficient, microcontroller level core, named peripheral core.</p></div><div><p> </p></div><div><p>To execute commodity OS on a peripheral core, existing approaches either require much engineering effort or incur high execution cost. Therefore, we proposed a new OS model called transkernel. By utilizing cross-ISA dynamic binary translation (DBT) technique, transkernel creates a virtualized environment on the peripheral core. It relies on a small set of stable interfaces. It is specialized for frequently executed kernel path. It exploits ISA similarities to reduce DBT overhead.</p></div><div><p> </p></div><div><p>We implement a transkernel model on ARM platform. With novel design and optimization, we demonstrate that a transkernel can gain energy efficiency. Moreover, it provides a new OS design to harness heterogeneous SoCs.</p></div>

The aim of this magister thesis is to examine the motives behind parents´ choice to sex determine their children, or not, at routine ultrasound examination (RUL). The analysed empirical data consists of 261 responding questionnaires written by expecting parents. My conclusions are that the motives behind parents’ choice can reflect their view of sex as binary or analog. Many parents sex determine their unborn children in order for preparing their rooms, clothes and toys to correlate with the heterosexual matrix. Girls get pink and boys blue, but the colours are of course only the visible part of how children are sexed as social construction. Some parents are experiencing a peer pressure and quite a few parents are influenced by the midwife performing the RUL to chose to sex determine their child. The most common motive to abstain from sex determining the child at RUL is after all to make gender the big happening at birth. Parents prepare to raise – not a child – but a boy or girl.

Student Number : 9708525G - PhD thesis - School of Mathematics - Faculty of Science / Sequences of numbers have important applications in the field of Computer Science. As a result they have become increasingly regarded in Mathematics, since analysis can be instrumental in investigating algorithms. Three concepts are discussed in this thesis, all of which are concerned with ‘words’ or ‘sequences’ of natural numbers where repeated letters are allowed: • The number of distinct values in a sequence with geometric distri- bution In Part I, a sample which is geometrically distributed is considered, with the objective of counting how many different letters occur at least once in the sample. It is concluded that the number of distinct letters grows like log n as n → ∞. This is then generalised to the question of how many letters occur at least b times in a word. • The position of the maximum (and/or minimum) in a sequence with geometric distribution Part II involves many variations on the central theme which addresses the question: “What is the probability that the maximum in a geometrically distributed sample occurs in the first d letters of a word of length n?” (assuming d ≤ n). Initially, d is considered fixed, but in later chapters d is allowed to grow with n. It is found that for 1 ≤ d = o(n), the results are the same as when d is fixed. • The average depth of a key in a binary search tree formed from a sequence with repeated entries Lastly, in Part III, random sequences are examined where repeated letters are allowed. First, the average left-going depth of the first one is found, and later the right-going path to the first r if the alphabet is {1, . . . , r} is examined. The final chapter uses a merge (or ‘shuffle’) operator to obtain the average depth of an arbitrary node, which can be expressed in terms of the left-going and right-going depths.

Les nébuleuses planétaires (NP) sont le produit de l'évolution d'étoiles de masses intermédiaires après leur expansion sphérique à la fin de leurs vies. Il a été estimé observationnellement que 80 % des NP ont des formes non-sphériques. Une fraction si élevée est déroutante et a mobilisé la communauté de recherche sur les NP pendant plus de trente ans. Un scénario qui permettrait de justifier les formes observées serait que les étoiles progénitrices de noyaux de NP (NNP) ne sont pas simples, mais possèdent un compagnon. Les formes des nébuleuses seraient ainsi le résultat de l'interaction avec le compagnon. La fraction si élevée de NP non-sphériques impliquerait donc une fraction élevée de NNP binaires, faisant de la parité stellaire un canal de formation privilégié pour les NP. Après avoir présenté l'état de connaissance actuelle concernant la formation et la mise en forme des NP, je présente mes travaux visant à détecter un excès infrarouge qui serait la signature de la présence d'un compagnon orbitant le NNP. La première partie de ce projet consiste en l'analyse de données et photométrie acquises par moi-même. Dans la deuxième partie je présente une tentative d'utilisation de jeux de données d'archives : la campagne optique Sloan Digital Sky Survey Data Release 7 et la version étendue de la base de données assemblée par Frew (2008). Je présente aussi les résultats d'une analyse de vitesses radiales de spectres VLT/UVES pour 14 NNP dans le but de détecter des compagnons spectroscopiques. Finalement j'expose les détails d'une analyse de photométrie de données optiques dans le but de détecter des compagnons orbitant autour de NNP en utilisant la technique de variabilité photométrique. Le résultat principal de cette thèse réside dans les analyses d'excès infrarouge proche que je combine avec des données publiées précédemment. Je conclus que si la fraction détectée d'excès infrarouge proche est attribuée à la présence de compagnons stellaires, alors la fraction binaire de NNP est plus grande que celle attendue en se basant sur la population binaire de progéniteurs de la séquence principale et ainsi conclus que la multiplicité stellaire est un canal de formation privilégié pour la formation des NP. Je clos en soulignant la nécessité d'un échantillon d'étude d'environ 150 objets pour réduire l'incertitude sur la fraction binaire et appuyer les conclusions statistiques de ce résultat. / Planetary nebulae (PNe) are the products of the evolution of intermediate mass stars that have expanded spherically at the end of their lives. Observationally, it has been estimated that 80% of them have non-spherical shapes. Such a high fraction is puzzling and has occupied the PN community for more than 30 years. One scenario that would allow to justify the observed shapes is that a comparable fraction of the progenitors of central stars of PN (CSPN) are not single, but possess a companion. The shape of the nebulae would then be the result of an interaction with this companion. The high fraction of non-spherical PNe would thus imply a high fraction of binary CSPN, making binarity a preferred channel for PN formation. After presenting the current state of knowledge regarding PN formation and shaping and reviewing the diverse efforts to find binaries in PNe, I present my work to detect a near-infrared excess that would be the signature of the presence of cool companions. The first part of the project consists in the analysis of data and photometry acquired and conducted by myself. The second part details an attempt to make use of archived datasets: the Sloan Digital Sky Survey Data Release 7 optical survey and the extended database assembled by Frew (2008). I also present results from a radial velocity analysis of VLT/UVES spectra for 14 objects aiming to the detection of spectroscopic companions. Finally I give details of the analysis of optical photometry data from our observations associated to the detection of companions around CSPN using the photometric variability technique. The main result of this thesis is from the near-infrared excess studies which I combine with previously-published data. I conclude that the if the detected red and NIR flux excess is indicative of a stellar companion then the binary fraction is larger than what we may expect based on the main-sequence progenitor population binary fraction and therefore conclude that binarity is a preferential channel for the formation of PN. I finish by underlining the need for a sample size of ∼ 150 objects to decrease the uncertainty on the PN population binary fraction and increase the statistical significance of this result.

Procedural Content Generation innebär att spelinnehåll automatiskt genereras för att dels både öka variationen i spel dels och minska arbetsbelastningen hos designers. Ett användningsområde för detta är rumbaserad bangenerering. Målet med detta  här arbetet är var att jämföra två algoritmer som gör just detta:; Binary Space Partitioning och Delaunay Triangulation. De kriterier som algoritmerna utvärderades på var tidseffektivitet, variation, likhet och möjligheten att nå alla rum. Resultatet visade att Binary Space Partitioning hade snabbare genereringstid samtidigt som Delaunay Triangulation gav utvecklaren mer valmöjligheter. Vilken algoritm som var att föredra ifall tidsaspekten inte bar mest tyngd blev helt en en mestadels subjektiv fråga där varje enskild utvecklares önskemål kommer påverka svaret. Ifall arbetet skulle fortsättas i framtiden skulle det vara intressant att utföra fler tester med flera olika mätvärden samt använda algoritmerna i ett spel och sedan påta låta spelare testare bedöma kvalitén hos banorna som genereras.