<p>This paper deals with performance measurements in 802.11g Wireless Multi-Hop Net- </p><p>works at different locations. After an introduction to 802.11g Wireless LANs and </p><p>Wireless Multi-Hop Networks, the testing environment consisting of hardware, soft- </p><p>ware, configuration, and three different locations is described. Before test series for the </p><p>actual measurements are defined, carried out reference tests provide reference perfor- </p><p>mance data and prove that the used hardware is suitable for testing Wireless Multi-Hop </p><p>Networks. Then the results of the measurements are discussed which show the influ- </p><p>ence of multiple hops on throughput and latency for single and multi channel Multi-Hop </p><p>Networks in indoor, outdoor, and urban environment. Finally, an outlook to further </p><p>tests and improvements of Wireless Multi-Hop Networks is given.</p>

This paper deals with performance measurements in 802.11g Wireless Multi-Hop Net- works at different locations. After an introduction to 802.11g Wireless LANs and Wireless Multi-Hop Networks, the testing environment consisting of hardware, soft- ware, configuration, and three different locations is described. Before test series for the actual measurements are defined, carried out reference tests provide reference perfor- mance data and prove that the used hardware is suitable for testing Wireless Multi-Hop Networks. Then the results of the measurements are discussed which show the influ- ence of multiple hops on throughput and latency for single and multi channel Multi-Hop Networks in indoor, outdoor, and urban environment. Finally, an outlook to further tests and improvements of Wireless Multi-Hop Networks is given.

Populations often experience environmental conditions that are variable both in space and in time. Understanding the demographic and evolutionary dynamics of populations in such variable environments has very practical implications for conservation biology, pest and pathogen control, management of antibiotic resistance. This thesis is an attempt to study the ecological and evolutionary implications of spatial and temporal variations of the environment.First, I study how spatially heterogeneous and temporally changing conditions influence the demographic dynamics of a genetically uniform population. The growth of the population is enhanced when individuals preferentially accumulate in high quality habitats. Migration between locations facilitates a good arrangement of individuals such that in general, an intermediate rate of migration maximizes the growth rate.Second, I develop a model where the growth rate of individuals depends on the environment but also on their genetic quality, and possibly on the interaction between the environment and the genotype. If the performance of different genotypes tradeoffs across the environments, several genotypes may be maintained locally in the environment that suit them and a pattern of local adaptation emerges. Moreover, I show that adaptation of populations to environmental fluctuations in the environment generates very dynamic changes in the genetic composition that lag behind the environmental change. Adaptation may be facilitated by the influx of migrants coming from other demes.How can we detect such patterns of adaptation in wild or experimental populations? I develop a formal analysis of several experimental and statistical techniques that are used to detect patterns of local and temporal adaptation. I provide recommendations regarding efficient experimental designs and statistical techniques to detect local adaptation. I also develop a new framework for the analysis of patterns of adaptation in time. I illustrate the potential use of this approach using a data set measuring the adaptation of HIV to the immune response of several recently infected patients. / Populations often experience environmental conditions that are variable both in space and in time. Understanding the demographic and evolutionary dynamics of populations in such variable environments has very practical implications for conservation biology, pest and pathogen control, management of antibiotic resistance. This thesis is an attempt to study the ecological and evolutionary implications of spatial and temporal variations of the environment.First, I study how spatially heterogeneous and temporally changing conditions influence the demographic dynamics of a genetically uniform population. The growth of the population is enhanced when individuals preferentially accumulate in high quality habitats. Migration between locations facilitates a good arrangement of individuals such that in general, an intermediate rate of migration maximizes the growth rate.Second, I develop a model where the growth rate of individuals depends on the environment but also on their genetic quality, and possibly on the interaction between the environment and the genotype. If the performance of different genotypes tradeoffs across the environments, several genotypes may be maintained locally in the environment that suit them and a pattern of local adaptation emerges. Moreover, I show that adaptation of populations to environmental fluctuations in the environment generates very dynamic changes in the genetic composition that lag behind the environmental change. Adaptation may be facilitated by the influx of migrants coming from other demes.How can we detect such patterns of adaptation in wild or experimental populations? I develop a formal analysis of several experimental and statistical techniques that are used to detect patterns of local and temporal adaptation. I provide recommendations regarding efficient experimental designs and statistical techniques to detect local adaptation. I also develop a new framework for the analysis of patterns of adaptation in time. I illustrate the potential use of this approach using a data set measuring the adaptation of HIV to the immune response of several recently infected patients.

Real-world optimisation problems often are of a dynamic nature. Recently, much research has been done to apply particle swarm optimisation (PSO) to dynamic environments (DE). However, these research efforts generally focused on optimising one variation of the PSO algorithm for one type of DE. The aim of this work is to develop a more comprehensive view of PSO for DEs. This thesis studies different schemes of characterising and taxonomising DEs, performance measures used to quantify the performance of optimisation algorithms applied to DEs, various adaptations of PSO to apply PSO to DEs, and the effectiveness of these approaches on different DE types. The standard PSO algorithm has shown limitations when applied to DEs. To overcome these limitations, the standard PSO can be modi ed using personal best reevaluation, change detection and response, diversity maintenance, or swarm sub-division and parallel tracking of optima. To investigate the strengths and weaknesses of these approaches, a representative sample of algorithms, namely, the standard PSO, re-evaluating PSO, reinitialising PSO, atomic PSO (APSO), quantum swarm optimisation (QSO), multi-swarm, and self-adapting multi-swarm (SAMS), are empirically analysed. These algorithms are analysed on a range of DE test cases, and their ability to detect and track optima are evaluated using performance measures designed for DEs. The experiments show that QSO, multi-swarm and reinitialising PSO provide the best results. However, the most effective approach to use depends on the dimensionality, modality and type of the DEs, as well as on the objective of the algorithm. A number of observations are also made regarding the behaviour of the swarms, and the influence of certain control parameters of the algorithms evaluated. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Computer Science / unrestricted

Access to credit in the changing environment is the primary challenge to survival for many small and medium-sized enterprise (SME) owners. The purpose of this multicase study was to understand how seasoned small business leaders in wholesaling and manufacturing in Northwest Arkansas strategically adapted to obtaining access to credit in an environment of bank mergers and acquisitions, disruptive information technology, federal and state regulations, and globalization. The conceptual framework that grounded this study was adaptive leadership and change management. Although, small business leaders prefer to obtain credit from community banks through relationship financing, leaders of SMEs can adapt to the challenges of the changing environment. The data collection process involved face-to-face, onsite, semistructured interviews of 5 participant SME owners selected via purposive sampling throughout the Northwest Arkansas region. Analysis of the transcripts involved coding data into groups using keyword identification and regrouping the data into themes. Themes that emerged from the study included the importance of formalizing a capital strategy, utilizing alternative forms of financing, and responding and adapting to change. Also, small business owners use financial software to provide technical, financial reports, and pro forma statements with variance analysis. Positive social change from the findings of this study may develop through SMEs' potential to increase job provision thereby benefiting workers' families with better employment opportunities, enhancing public infrastructure through greater tax revenues, and generating a long-term, viable, sustainable future to the region's public education through an increased tax base.

[pt] Robôs móveis são cada dia mais importantes na sociedade moderna, realizando tarefas consideradas tediosas ou muito repetitivas para humanos, como limpeza ou patrulhamento. A maioria dessas tarefas requer um certo nível de autonomia do robô. Para que o robô seja considerado autônomo, ele precisa de um mapa do ambiente, e de sua posição e orientação nesse mapa. O problema de localização e mapeamento simultâneos (SLAM) é a tarefa de estimar tanto o mapa quanto a posição e orientação simultaneamente, usando somente informações dos sensores, sem ajuda externa. O problema de SLAM visual consiste na tarefa de realizar SLAM usando somente câmeras para o sensoriamento. A maior vantagem de usar câmeras é a possibilidade de resolver problemas de visão computacional que provêm informações de alto nível sobre a cena, como detecção de objetos. Porém a maioria dos sistemas de SLAM visual assume um ambiente estático, o que impõe limitações para a sua aplicabilidade em cenários reais. Esta tese apresenta soluções para o problema de SLAM visual em ambientes dinâmicos e em mudança. Especificamente, a tese propõe um método para ambientes com multidões, junto com um detector de pessoas customizado baseado em aprendizado profundo. Além disso, também é proposto um método de SLAM visual para ambientes altamente dinâmicos contendo objetos em movimento, combinando um rastreador de objetos robusto com um algoritmo de filtragem de pontos. Além disso, esta tese propõe um método de SLAM visual para ambientes em mudança, isto é, em cenas onde os objetos podem mudar de lugar após o robô já os ter mapeado. Todos os métodos propostos são testados com dados públicos e experimentos, e comparados com diversos métodos da literatura, alcançando um bom desempenho em tempo real. / [en] Mobile robots have become increasingly important in modern society, as they can perform tasks that are tedious or too repetitive for humans, such as cleaning and patrolling. Most of these tasks require a certain level of autonomy of the robot. To be fully autonomous and perform navigation, the robot needs a map of the environment and its pose within this map. The Simultaneous Localization and Mapping (SLAM) problem is the task of estimating both map and localization, simultaneously, only using sensor measurements. The visual SLAM problem is the task of performing SLAM only using cameras for sensing. The main advantage of using cameras is the possibility of solving computer vision problems that provide high-level information about the scene, such as object detection. However, most visual SLAM systems assume a static environment, which imposes a limitation on their applicability in real-world scenarios. This thesis presents solutions to the visual SLAM problem in dynamic and changing environments. A custom deep learning-based people detector allows our solution to deal with crowded environments. Also, a combination of a robust object tracker and a filtering algorithm enables our visual SLAM system to perform well in highly dynamic environments containing moving objects. Furthermore, this thesis proposes a visual SLAM method for changing environments, i.e., in scenes where the objects are moved after the robot has already mapped them. All proposed methods are tested in datasets and experiments and compared with several state-of-the-art methods, achieving high accuracy in real time.

When a new transport service is introduced, people have to learn and familiarize themselves with the new service before they decide to adopt it. These processes are developed over time, thus produce dynamics in individuals’ behavioural responses towards the service. This affects the demand of the new service, thus affect revenues. Available studies have examined the factors influencing these responses from microeconomic perspectives. The influence of the theory-based subjective factors has not been examined empirically. Understanding these would assist transport and urban planners to design a better marketing strategy to increase the market share of the new service. A change in seasons affect individuals’ activity-travel decisions, thus produce dynamics in activitytravel patterns in different seasons. Individuals’ constraints, in a form of mandatory activities (working/studying), are influencing individuals’ decisions to participate in day-to-day nonmandatory activities (leisure and routine activities). The interdependency between travel demand, time allocation and mode choice that considers interactions between mandatory and non-mandatory activities, in different seasons is less explored. Understanding these would assist transport planners and operators to manage travel demand strategies across different seasons of the year and provide better transportation systems for all individuals. This thesis includes five papers. Paper I explores individuals’ characteristics of the quick-response and the adopters of the new public transport (PT) service and examines the temporal effects. Paper II investigates the subjective factors influencing a quick-response to the new PT service by proposing a modified attitude-behaviour framework. Paper III and IV analyse the effects of seasonal variations and individuals’ constraints on their day-to-day activity-travel decisions and patterns. Paper V analyses the attrition and fatigue in the two-week travel diary panel survey instrument. / <p>QC 20170323</p>