The increased demand on wireless applications, coupled with the current inefficiency in spectrum usage, mandate a new communication paradigm shift from fixed spectrum assignment to dynamic spectrum sharing which can be achieved using the cognitive radio technology. Cognitive radio allows unlicensed secondary nodes to form communication links over licensed spectrum bands on an opportunistic basis which increases the spectrum management efficiency. Cognitive radio networks (CRN), however, impose unique challenges due to the fluctuation in the available spectrum as well as the diverse quality of service requirements. One of the main challenges is the establishment and maintenance of routes in multi-hop CRNs. In this thesis, we critically investigate the problem of routing in multi-hop CRNs. The main objective of this research is to maximize network connectivity while limiting routing delay. We developed a general connectivity metric for single-band and multi-band CRNs based on the properties of the Laplacian matrix eigenvalues spectrum. We show through analytical and simulation results that the developed metric is more robust and has lower computational complexity than the previously proposed metrics. Furthermore, we propose a new position-based routing algorithm for large scale CRNs which significantly reduces the routing computational complexity with negligible performance degradation compared to the traditional full node search algorithm. In addition, the connectivity metric developed in this thesis is used to develop a connectivity-aware distributed routing protocol for CRNs. Finally, we use a commodity cognitive radio testbed to demonstrate the concept of CR Wi-Fi networks.

Near infrared spectroscopy (NIRS) is an emerging neuroimaging modality with high temporal and good spatial resolution. In this thesis, NIRS was applied to understand functionality of the fronto-temporal cortex in response to language-related tasks. A 32-channel NIRS system (Imagent ISS Inc.) was used to perform experimental studies on 15 right-handed normal adults. Block-design based Word Expression and Word Reception paradigms were independently presented to participants. Activation, functional connectivity and cortical lateralization analyses were performed. From word expression studies, results showed left anterior region (encompassing Broca) is majorly involved over right homologue and posterior regions. From the word reception studies, results showed that right posterior region (encompassing right homologue of Wernicke) is highly involved in language reception, with right anterior region (encompassing right homologue of Broca) also involved. The current study has potential future applications in surgical evaluation of language regions in populations with neurological disorders such as epilepsy, and schizophrenia.

While geographic distance is a variable often used to explain population genetic differentiation, dynamic processes leading to stochastic population structure are more likely driving factors. The following thesis presents the population structure of a common reef sponge, Stylissa carteri, and yields hypotheses on the influence of environmental heterogeneity as a predictor of the observed population structure. This project represents the largest population genetics study thus conducted in the Red Sea and also includes the first population genetics data gathered for sites off the coast of Sudan and Soccotra. The study herein presented includes both a large scale (36 reef sites covering over 1000km of coastline) and small-scale (16 transects of 50m each) analysis of gene flow in a benthic dwelling organism. The variable effect of geography and environmental conditions on S. carteri population structure is assessed using a seascape genetics approach. Environmental factors from a nine-year dataset accessed from the NASA Giovanni website including chlorophyll a, sea surface temperature, dissolved and particulate organic matter for both the annual and winter temporal scale were considered.

Marine protected areas (MPAs) have proliferated in the past decades to protect biodiversity and sustain fisheries. However, most of the MPA networks have been designed without taking into account a critical factor: the larval dispersal patterns of populations within and outside the reserves. The scale and predictability of larval dispersal, however, remain unknown due to the difficulty of measuring dispersal when larvae are minute (~ cm) compared to the potential scale of dispersal (~ km). Nevertheless, genetic approaches can now be used to make estimates of larval dispersal. The following thesis describes self-recruitment and connectivity patterns of a coral reef fish species (Centropyge bicolor) in Kimbe Bay, Papua New Guinea. To do this, microsatellite markers were developed to evaluate fine-scale genetics and recruit assignment via genetic parentage analysis. In this method, offspring are assigned to potential parents, so that larval dispersal distances can then be inferred for each individual larvae. From a total of 255 adults and 426 juveniles collected only 2 parentoffspring pairs were assigned, representing less than 1% self-recruitment. Previous data from the same study system showed that both Chaetodon vagagundus and Amphiprion percula have consistent high self-recuitment rates (~ 60%), despite having contrasting life history traits. Since C. bicolor and C. vagabundus have similar characteristics (e.g. reproductive mode, pelagic larval duration), comparable results were expected. On the contrary, the results of this study showed that dispersal patterns cannot be generalized across species. Hence the importance of studying different species and seascapes to better understand the patterns of larval dispersal. This, in turn, will be essential to improve the design and implementation of MPAs as conservation and management tools.

Cougars (Puma concolor) have been recolonizing Midwestern North America over the past 2 decades with >950 cougar confirmations east of established populations. Management and public interest in habitat suitability and connectivity east of current cougar range have grown as confirmations increase and models predicting habitat connectivity and population viability for the Midwest show potential for breeding populations. However, although long-range dispersal and recolonization continues, no studies have assessed potential habitat associated with cougars throughout their historical range in eastern North America. I used ArcGIS, the Analytical Hierarchy Process, and geospatial data to model cougar habitat and potential dispersal corridors in eastern North America. The total amount of potential habitat was >2,400,000 km2 and mean patch size was 257,500 km2. Patches of habitat ranged in size from 3,868 km2 (Ozark Mountains) to >2,490,850 km2 (central and eastern Canada) with ≤53,643 km of dispersal corridors connecting patches. With cougars potentially recolonizing areas previously devoid of large carnivores, public acceptance of management efforts is pivotal for the success of their recolonization. However, targeted surveys assessing public perceptions and knowledge of cougars and red wolves (Canis rufus), who have faced similar extirpation in the Southeastern United States are limited. I mailed 20,000 questionnaires and 2,000 follow-up postcards to residents near areas of potential red wolf and cougar habitat in the Southeastern United States in 2020. I used cumulative link models to gauge the associations between sociodemographic predictor with respondent’s knowledge and attitude towards large carnivores. Total response rate was 4.6% with the majority of respondents identifying as male (53.6%), having a 4-year degree or above (54.1%), and 57 ± 16 (SE) years of age. Respondents’ knowledge and attitudes towards large carnivores were largely positive (≥63% positive) with higher education, older age, and current livestock ownership being largest predictors for responses. Attitudes towards red wolves were largely driven by knowledge of red wolves while attitudes towards cougars were primarily driven by livestock ownership. Livestock owners (71.5%) were concerned about safety of livestock in large carnivore habitat, and most respondents (61%) did not trust their local agency to effectively manage large carnivore populations. My research provides a foundation for wildlife managers to develop informed plans, educational programs, and policy decisions for potentially recolonizing large carnivore populations.

This study dealt with the issue of sustainability of ICT4D initiatives being a problem with few success stories (Heeks, 2002, Toyama, 2010). Many of these initiatives were planned and executed in a top-down fashion by large funders and governments, and these failures have stimulated the search for new strategies to achieve long-term sustainability. One possible approach is to consider the different levels of systems that are involved. The reasons for failure lie inside the scope of a project, within the community itself, and outside the community in the larger socio-economic system which includes the economy. A systems approach with respect to the analysis of the sustainability (or lack thereof) of development initiatives was therefore adopted. The Choice Framework of Dorothea Kleine (2010) was used since it is a systemic approach, developed in the study of ICT4D initiatives, that embraces the complexity of engaging with development paradigms, societal structures and personal agency. The research was done on a large South African government initiative, the Broadband-for-All (BB4All), community-based wireless mesh network project which aimed to provide a cost-effective way of enabling reliable broadband connectivity in rural areas. The project had two key aspects, the provision of a large-scale demonstrator of a wireless mesh network (WMN) as a broadband solution and the establishment of a Village Operator (VO) model to support access to and increase the use of the technology. The teachers and learners in more than 170 schools were the primary customers. Young people from local communities were trained as VOs to become local entrepreneurs (micro-enterprises) responsible for operating and supporting the BB4All service in their assigned cluster of schools and respective communities. The research focus was the sustainability of the VOs. The Choice Framework was used to provide a context for the research regarding the role played by social resources (social capital) in contributing to the sustainability of the VO micro-enterprises. In-depth interviews were held with all but one of the 15 VOs in order to develop an understanding of their social capital and the influence thereof on them as entrepreneurs. The importance and usefulness of social capital in supporting sustainability at VO and initiative level was analysed. Three major themes emerged that were analysed in detail, namely, the role of social capital, community service and social entrepreneurship, as well as the development of networks of innovation. At a theoretical level, the research reflected on implications of the findings for the role of social capital in the Choice Framework. At a practical level, considerations for using a social capital perspective in order to improve the conceptualisation, design, implementation and transfer of ICT4D initiatives for sustainability were developed. / Thesis (PhD)--University of Pretoria, 2016. / Informatics / PhD / Unrestricted

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A vertex cover of a given graph is a vertex set including at least one endpoint from every edge. A vertex cover number τ is the size of a minimum vertex cover. If the vertices from a vertex cover are required to induce a connected subgraph, the resulting set is called a connected vertex cover. The corresponding parameter τc is called a connected vertex cover number. The decision versions of both problems are NP-complete. To better understand a relation between these two vertex cover numbers, Cardinal and Levy define the price of connectivity as a ratio between τc and τ. It is not surprising that determining whether the price of connectivity of a given graph is at most t is NP- hard. The notion of price of connectivity can be extended for more graph properties, such as for the dominating set. The price of connectivity has already been investigated in several papers, with some focusing on critical graphs whose price of connectivity is strictly greater than the price of connectivity of every induced subgraph. This thesis provides an overview of the current state of research into the price of connectivity. Moreover, we focus on the structural properties of critical graphs for the price of connectivity for vertex cover and discuss a possible characterization of graphs in which the price of connectivity for a...

Understanding how communication between brain areas evolves to support dynamic function remains a fundamental challenge in neuroscience. One approach to this question is functional connectivity analysis, in which statistical coupling measures are employed to detect signatures of interactions between brain regions. Because the brain uses multiple communication mechanisms at different temporal and spatial scales, and because the neuronal signatures of communication are often weak, powerful connectivity inference methodologies require continued development specific to these challenges. Here we address the challenge of inferring task-related functional connectivity in brain voltage recordings. We first develop a framework for detecting changes in statistical coupling that occur reliably in a task relative to a baseline period. The framework characterizes the dynamics of connectivity changes, allows inference on multiple spatial scales, and assesses statistical uncertainty. This general framework is modular and applicable to a wide range of tasks and research questions. We demonstrate the flexibility of the framework in the second part of this thesis, in which we refine the coupling statistics and hypothesis tests to improve statistical power and test different proposed connectivity mechanisms. In particular, we introduce frequency domain coupling measures and define test statistics that exploit theoretical properties and capture known sampling variability. The resulting test statistics use correlation, coherence, canonical correlation, and canonical coherence to infer task-related changes in coupling. Because canonical correlation and canonical coherence are not commonly used in functional connectivity analyses, we derive the theoretical values and statistical estimators for these measures. In the third part of this thesis, we present a sample application of these techniques to electrocorticography data collected during an overt reading task. We discuss the challenges that arise with task-related human data, which is often noisy and underpowered, and present functional connectivity results in the context of traditional and contemporary within-electrode analytics. In two of nine subjects we observe time-domain and frequency-domain network changes that accord with theoretical models of information routing during motor processing. Taken together, this work contributes a methodological framework for inferring task-related functional connectivity across spatial and temporal scales, and supports insight into the rapid, dynamic functional coupling of human speech.

Sensors are light-weight, low powered devices that measure some aspect of a physical or virtual environment and transmit this information in some format. This thesis describes how to integrate a sensor onto devices to enable network connectivity. The phrase “internet of things” suggests that within a few years many devices will be connected to an internet. Devices, including common household appliances, will transmit and receive data over a network. The CEO of Ericsson has stated that there will be more than 50 billion connected devices by 2020[1]. These devices could be microwaves, fridges, lights, or temperature sensors. Devices that are usually not associated with internet connectivity will be integrated into networks and play a larger role in providing information and controlling other devices. Sensors will have a major role in “the internet of things”. These small computers could be integrated in any appliances and transmit data over the network. The sensors’ low power and low cost, as well as their light weight, makes them very attractive to integrate them into many devices. The goal of this thesis project is to build upon this trend toward “The internet of things” by integrating a sensor into a bathroom scale thus enabling the scale to have networking connectivity. The sensor will be low cost and simple. It should wirelessly or via USB transmit the current weight that it measures to a receiver (specifically a gateway). This gateway will forward the message over the network to a website or mobile phone for visual presentation of the data. This thesis describes different techniques and approaches toward developing this sensor. The thesis also evaluates these different choices in order to select one technique that will be implemented. This solution will be evaluated in terms of its cost and ease of integration into an existing commercially produced scale. / Sensorer är små, energieffektiva apparater som upptäcker variationer i förhållande till någon stimulans och skickar informationen i ett godtyckligt format. Den här uppsatsen beskriver hur man kan integrera en sensor med en apparat för att möjliggöra nätverksuppkoppling. Uttrycket ”The Internet of things”, översatt på svenska som ”Internet av saker”, konstaterar att inom några år så kommer den mesta av vardaglig elektronik vara uppkopplad mot Internet. Hemelektroniken kommer att skicka och ta emot data över ett nätverk. Ericsson tror att det kommer att vara över 50 miljarder uppkopplade apparater år 2020[1]. Sådana apparater kan vara mikrovågsugnar, frysar, lampor eller termometrar. Apparater som vanligtvis inte förväntas vara uppkopplade mot ett nätverk kommer att bli uppkopplade för att tillföra eller kontrollera information och andra apparater. Sensorer har en viktig roll i denna utveckling. De är små datorer som kan kopplas upp mot flertalet elektroniska apparater och förse dem med en nätverksuppkoppling för att skicka betydelsefull data över ett nätverk. Energieffektiviteten och de låga kostnaderna, så väl som deras små storlekar, gör dem dessutom väldigt attraktiva. Målet med den här uppsatsen är att påbygga ”The Internet of things” genom att tillförse en personvåg med en sensor för att möjliggöra nätverksuppkoppling. Sensor ska vara enkel och billig. Den kommer att trådlöst eller via USB skicka vikter till en mottagare som sedan skickar vidare informationen över nätverket till en hemsida eller mobiltelefon för en grafisk presentation av informationen. Den här rapporten beskriver dem olika teknikerna och approachen mot utvecklingen av sensorn.