The term of Cognitive Radio (CR) used to indicate that spectrum radio could be accessed dynamically and opportunistically by unlicensed users. In CR Networks, Interference between nodes, hidden terminal problem, and spectrum sensing errors are big issues to be widely discussed in the research field nowadays. To improve the performance of such kind of networks, this thesis proposes Cognitive Medium Access Control (MAC) protocols for Mobile Ad-Hoc Networks (MANETs). From the concept of CR, this thesis has been able to develop a cognitive MAC framework in which a cognitive process consisting of cognitive elements is considered, which can make efficient decisions to optimise the CR network. In this context, three different scenarios to maximize the secondary user's throughput have been proposed. We found that the throughput improvement depends on the transition probabilities. However, considering the past information state of the spectrum can dramatically increases the secondary user's throughput by up to 40%. Moreover, by increasing the number of channels, the throughput of the network can be improved about 25%. Furthermore, to study the impact of Physical (PHY) Layer errors on cognitive MAC layer in MANETs, in this thesis, a Sensing Error-Aware MAC protocols for MANETs has been proposed. The developed model has been able to improve the MAC layer performance under the challenge of sensing errors. In this context, the proposed model examined two sensing error probabilities: the false alarm probability and the missed detection probability. The simulation results have shown that both probabilities could be adapted to maintain the false alarm probability at certain values to achieve good results. Finally, in this thesis, a cooperative sensing scheme with interference mitigation for Cognitive Wireless Mesh Networks (CogMesh) has been proposed. Moreover, a prioritybased traffic scenario to analyze the problem of packet delay and a novel technique for dynamic channel allocation in CogMesh is presented. Considering each channel in the system as a sub-server, the average delay of the users' packets is reduced and the cooperative sensing scenario dramatically increases the network throughput 50% more as the number of arrival rate is increased.

abstract: Magnetic Resonance Imaging using spiral trajectories has many advantages in speed, efficiency in data-acquistion and robustness to motion and flow related artifacts. The increase in sampling speed, however, requires high performance of the gradient system. Hardware inaccuracies from system delays and eddy currents can cause spatial and temporal distortions in the encoding gradient waveforms. This causes sampling discrepancies between the actual and the ideal k-space trajectory. Reconstruction assuming an ideal trajectory can result in shading and blurring artifacts in spiral images. Current methods to estimate such hardware errors require many modifications to the pulse sequence, phantom measurements or specialized hardware. This work presents a new method to estimate time-varying system delays for spiral-based trajectories. It requires a minor modification of a conventional stack-of-spirals sequence and analyzes data collected on three orthogonal cylinders. The method is fast, robust to off-resonance effects, requires no phantom measurements or specialized hardware and estimate variable system delays for the three gradient channels over the data-sampling period. The initial results are presented for acquired phantom and in-vivo data, which show a substantial reduction in the artifacts and improvement in the image quality. / Dissertation/Thesis / M.S. Bioengineering 2013

Tato práce je přehledem zpožděných diferenciálních rovnic v dynamických systémech. Počínaje obecným přehledem zpožděných diferenciálních rovnic představujeme koncept zpožděných diferenciálů a použití jeho modelů, od biologie a populační dynamiky po fyziku a inženýrství. Poskytneme také přehled Dynamické systémy a diferenciální rovnice zpoždění v dynamických systémech. Oblastí pro modelování s rovnicemi zpožďovacích diferenciálů je Epidemiologie. Důraz je kladen na vývoj epidemiologického modelu Susceptible-Infected-Removed (SIR) bez časového zpoždění. Analyzujeme naše dva modely v rovnováze a lokální stabilitě pomocí předpokládaných dat COVID -19. Výsledky by byly porovnány mezi modelem bez zpoždění a modelem se zpožděním.

BACKGROUND: The prevalence of tuberculosis (TB) has been rapidly on the ascendency in the recent years globally due to its co-infection with HIV/AIDS. TB case finding is one of the technical pillars of the Directly Observed Treatment Short course (DOTS) TB strategy and there has been advocacy for early TB case detection to be the new focus of TB control efforts. PURPOSE: The purpose of this non-experimental study was to assess the determinants of TB case finding among pulmonary TB patients registered for treatment in Makana Municipality METHOD: A quantitative, non-experimental, cross sectional descriptive study among PTB patients registered for treatment at the primary health care clinics in Makana Municipality was done. Data collection was by self-administered questionnaires while sampling was by systematic sampling of PTB patients at five systematically selected clinics. RESULTS: Patient–related delay contributed more to total delay, in this study sample, than health system-related delay. Health system delay was found to be significantly associated with poorer finances, passive smoking history, seeking care from multiple health providers, initially visiting a non- NTCP health provider, TB stigma , overcrowding in the household and having difficulty with breathing as an initial symptom (p<0.05). CONCLUSION: There was a significant delay in TB case finding among PTB patients in this local municipality and patient related determinants contributed more than health system related determinants to this delay. There is need for the municipal TB programme to embark on an aggressive health education programme to furnish the populace with accurate information about TB, improve their health seeking behaviour and help address the issue of stigma associated with TB. / Health Studies

Observed influences of system response delay in spoken human-machine dialogues are rather ambiguous and mainly focus on perceived system quality. Studies that systematically inspect effects on cognitive performance are still lacking, and effects of individual characteristics are also often neglected. Building on benefits of cognitive training for decelerating cognitive decline, this Wizard-of-Oz study addresses both issues by testing 62 elderly participants in a dialogue-based memory training with a virtual agent. Participants acquired the method of loci with fading instructional guidance and applied it afterward to memorizing and recalling lists of German nouns. System response delays were randomly assigned, and training performance was included as potential mediator. Participants’ age, gender, and subscales of affinity for technology (enthusiasm, competence, positive and negative perception of technology) were inspected as potential moderators. The results indicated positive effects on recall performance with higher training performance, female gender, and less negative perception of technology. Additionally, memory retention and facets of affinity for technology moderated increasing system response delays. Participants also provided higher ratings in perceived system quality with higher enthusiasm for technology but reported increasing frustration with a more positive perception of technology. Potential explanations and implications for the design of spoken dialogue systems are discussed.

BACKGROUND: The prevalence of tuberculosis (TB) has been rapidly on the ascendency in the recent years globally due to its co-infection with HIV/AIDS. TB case finding is one of the technical pillars of the Directly Observed Treatment Short course (DOTS) TB strategy and there has been advocacy for early TB case detection to be the new focus of TB control efforts. PURPOSE: The purpose of this non-experimental study was to assess the determinants of TB case finding among pulmonary TB patients registered for treatment in Makana Municipality METHOD: A quantitative, non-experimental, cross sectional descriptive study among PTB patients registered for treatment at the primary health care clinics in Makana Municipality was done. Data collection was by self-administered questionnaires while sampling was by systematic sampling of PTB patients at five systematically selected clinics. RESULTS: Patient–related delay contributed more to total delay, in this study sample, than health system-related delay. Health system delay was found to be significantly associated with poorer finances, passive smoking history, seeking care from multiple health providers, initially visiting a non- NTCP health provider, TB stigma , overcrowding in the household and having difficulty with breathing as an initial symptom (p<0.05). CONCLUSION: There was a significant delay in TB case finding among PTB patients in this local municipality and patient related determinants contributed more than health system related determinants to this delay. There is need for the municipal TB programme to embark on an aggressive health education programme to furnish the populace with accurate information about TB, improve their health seeking behaviour and help address the issue of stigma associated with TB. / Health Studies

This diploma thesis deals with adjusting the reverberation time of enclosed spaces. It is divided into two thematic areas. The first thematic area deals with active systems that adjust the reverberation time, with a stronger focus on usage of reverberators to simulate secondary spaces. The second thematic area is the implementation of reverberators and their fundamental building blocks in Matlab.