No description available.

The purpose of this research is twofold - the first objective being to develop Markovian models that can be used to analyze the performance of the various medium access control protocols of slotted ring type local area networks.

The Default Mode Network (DMN) is a large-scale brain network implicated in the control and monitoring of internal modes of cognition. The aim of this research was to investigate DMN function and its relationship to other large-scale cognitive control networks through functional connectivity analysis and analysis of combined electroencephalographic (EEG) recordings. Data utilised across a series of three experiments were obtained from combined EEG-functional Magnetic Resonance Imaging recordings acquired during technical development of a new scanner in the Clinical Research Centre, Ninewells Hospital, Dundee. Analyses were based on data acquired from neurologically healthy participants while they rested with their eyes-closed for five minutes. Following this, participants completed a 14-minute auditory attention task, designed to engage the dorsal and ventral attention networks. In this task, participants responded to task-relevant stimuli (odd/even numbers) and attempted to inhibit their responses to task-irrelevant ‘oddballs’ (the number ‘0’) and task-irrelevant/distractor stimuli (environment sounds). Experiment 1 utilised the simultaneous acquired EEG-fMRI resting-state data in order to establish whether EEG frequency content in the beta range (13-30 Hz) was a significant predictor of DMN activity (regions of which were identified on an individual basis using functional connectivity analysis). Results were comparable to existing literature showing there is inconsistency in establishing a reliable electrophysiological signature of the DMN. Experiment 1 also employed region-of-interest (ROI)-to-ROI functional connectivity analysis as a method of exploring the functional relationship between the DMN and: (1) a task-positive resting-state network; (2) other commonly identified DMN regions; and (3) regions covering the whole of the cerebral cortex. Results revealed networks were correlated at a component-based level and challenged existing literature which appears to over-generalise results from exploration of network interaction. Findings also revealed activation of specific DMN components were coupled with down-regulation of sensory-associated cortical regions. Experiment 2 analysed the fMRI data that were obtained from the auditory attention task in order to: (1) determine whether DMN activity was observed when participants were engaged in an externally-directed task; and (2) explore changes in DMN activity associated with increasing task duration. Results revealed that activation of the DMN was prominent and did not vary over three equal time periods. This supports existing research showing the DMN is a continuously active system (whose activity is modulated based on external-task demands). Results also hinted at the existence of possible relationships between the DMN and components of several other large-scale control networks. Therefore, in Experiment 3 potential interactions were explored using ROI-to-ROI functional connectivity analysis of the whole 14-minute time series. Firstly, functional connectivity within the dorsal/ventral attention, executive/frontoparietal control and salience networks was analysed; secondly, the relationships between putative regions of these networks and the DMN were analysed. Overall, results revealed that networks were functionally connected with one another at a component-based level only. This suggests flexible interaction between several large-scale control networks allows neurologically healthy participants to allocate resources to the simultaneous monitoring of the internal and external worlds.

No description available.

No description available.

The extent to which the knowledge mobilisation potential of public health networks is actually achieved in their functioning has not been previously studied. There are prescriptions from policy documents and from research literature as to the form networks in health should take and the way they should operate. However, there has been little research connecting the nature of the networks and the manner in which they function to their knowledge mobilising ability. Constituted in 2006, the Scottish Public Health Network (ScotPHN), which is the primary vehicle in Scotland for mobilising public health knowledge and informing policy and practice, constitutes the location for this study investigating this knowledge mobilisation and how networks function in public health. Feedback from the consultation conducted prior to the formation of ScotPHN was obtained. Interviews were conducted with the members of the ScotPHN steering group, a project group and the stakeholder group. Two ScotPHN steering group meetings were also attended by the author as an observer. The consultation feedback, transcripts of the interviews and those of steering group meetings were analysed using the constructivist version of the grounded theory approach. The process involved coding and abstracting codes to categories and themes. The emerging themes were reviewed in the light of existing literature on networks and knowledge mobilisation. These themes were then used to develop a model to understand how the network operates and consequently mobilises knowledge. The study shows that prior to its formation ScotPHN was expected to address the fragmentation of the public health workforce; significantly enhance links amongst existing public health networks; support ground level knowledge exchange amongst practitioners and significantly enhance multisectorial working. None of these expectations appear to have been met. ScotPHN has, however, managed to fill the gap left by the demise of the Scottish Needs Assessment Programme (SNAP). ScotPHN’s structure and the manner in which it is controlled lead to it being akin to a policy community rather than an issue network. The generic public health concerns of the steering group and the selective nature of the project group prevent it from functioning as an issue network. The dominance of people from the medical profession also causes a social closedness in the ScotPHN steering group. The limited multisectorial participation in its activities results in: a lack of constructionist learning; limited inclusion of the social context of knowledge; and a deficit of Mode 2 knowledge mobilisation. In the context of knowledge conversion there is some evidence of externalisation but no socialisation. ScotPHN is not a network that can be classed as a community of practice. This study highlights how health policies, which have advocated the establishment of networks, could derive considerable guidance from research into how networks actually function. With respect to the knowledge mobilisation activity of these networks the study finds that top-down and prescribed structures are unable to capture the transdisciplinarity and diverse intellectual frameworks that contribute to public health knowledge. It is seen that the hierarchical network structures can undermine the engagement of actors from the less represented sectors. Additionally the study finds that the established patterns of professional power and control further hinder multisectorial engagement.

Modem network control plane that supports versatile communication services (e.g. performance differentiation, access control, virtualization, etc.) is highly complex. Different control components such as routing protocols, security policy enforcers, resource allocation planners, quality of service modules, and more, are interacting with each other in the control plane to realize complicated control objectives. These different control components need to coordinate their actions, and sometimes they could even have conflicting goals which require careful handling. Furthermore, a lot of these existing components are distributed protocols running on large number of network devices. Because protocol state is distributed in the network, it is very difficult to tightly coordinate the actions of these distributed control components, thus inconsistent control actions could create serious problems in the network. As a result, such complexity makes it really difficult to ensure the optimality and consistency among all different components. Trying to address the complexity problem in the network control plane, researchers have proposed different approaches, and among these the centralized control plane architecture has become widely accepted as a key to solve the problem. By centralizing the control functionality into a single management station, we can minimize the state distributed in the network, thus have better control over the consistency of such state. However, the centralized architecture has fundamental limitations. First, the centralized architecture is more difficult to scale up to large network size or high requests rate. In addition, it is equally important to fairly service requests and maintain low request-handling latency, while at the same time having highly scalable throughput. Second, the centralized routing control is neither as responsive nor as robust to failures as distributed routing protocols. In order to enhance the responsiveness and robustness, one approach is to achieve the coordination between the centralized control plane and distributed routing protocols. In this thesis, we develop a centralized network control system, called Maestro, to solve the fundamental limitations of centralized network control plane. First we use Maestro as the central controller for a flow-based routing network, in which large number of requests are being sent to the controller at very high rate for processing. Such a network requires the central controller to be extremely scalable. Using Maestro, we systematically explore and study multiple design choices to optimally utilize modern multi-core processors, to fairly distribute computation resource, and to efficiently amortize unavoidable overhead. We show a Maestro design based on the abstraction that each individual thread services switches in a round-robin manner, can achieve excellent throughput scalability while maintaining far superior and near optimal max-min fairness. At the same time, low latency even at high throughput is achieved by Maestro's workload-adaptive request batching. Second, we use Maestro to achieve the coordination between centralized controls and distributed routing protocols in a network, to realize a hybrid control plane framework which is more responsive and robust than a pure centralized control plane, and more globally optimized and consistent than a pure distributed control plane. Effectively we get the advantages of both the centralized and the distributed solutions. Through experimental evaluations, we show that such coordination between the centralized controls and distributed routing protocols can improve the SLA compliance of the entire network.

Wireless networks promise ubiquitous communication, and thus facilitate an array of applications that positively impact human life. At a fundamental level, these networks deal with compression and transmission of sources over channels. Thus, accomplishing this task efficiently is the primary challenge shared by these applications. In practice, sources include data and video while channels include interference and relay networks. Hence, effective source and channel aware resource allocation for these scenarios would result in a comprehensive solution applicable to real-world networks. This dissertation studies the problem of source and channel aware resource allocation in certain scenarios. A framework for network resource allocation that stems from rate-distortion theory is presented. Then, an optimal decomposition into an application-layer compression control, a transport-layer congestion control and a network-layer scheduling is obtained. After deducing insights into compression and congestion control, the scheduling problem is explored in two cross-layer scenarios. First, appropriate queue architecture for cooperative relay networks is presented, and throughput-optimality of network algorithms that do not assume channel-fading and input-queue distributions are established. Second, decentralized algorithms that perform rate allocation, which achieve the same overall throughput region as optimal centralized algorithms, are derived. In network optimization, an underlying throughput region is assumed. Hence, improving this throughput region is the next logical step. This dissertation addresses this problem in the context of three significant classes of interference networks. First, degraded networks that capture highly correlated channels are explored, and the exact sum capacity of these networks is established. Next, multiple antenna networks in the presence of channel uncertainty are considered. For these networks, robust optimization problems that result from linear precoding are investigated, and efficient iterative algorithms are derived. Last, multi-cell time-division-duplex systems are studied in the context of corrupted channel estimates, and an efficient linear precoding to manage interference is developed. / text

This thesis presents a preliminary design of a fully articulated five-fingered anthropomorphic human hand prosthesis with particular emphasis on the controller and actuator design. The proposed controller is a modified artificial neural network PID-based controller with application to the nonlinear and highly coupled dynamics of the hand prosthesis. The new solid state actuator has been designed based on electroactive polymers, which are a type of material that exhibit electromechanical behavior and a liquid metal alloy acts as the electrode. The solid state actuators reduce the overall mechanical complexity, risk failure and required maintenance of the prosthesis. / Graduate

Com o desenvolvimento e disseminação dos protocolos de rede, o surgimento dos chips de ASIC e queda dos preços do silício (estes dois últimos fatores possibilitando com que os sensores e atuadores pudessem ser equipados com interfaces de rede e com isso se tornarem nós independentes em uma rede de controle em tempo real), viabilizaram o desenvolvimento dos sistemas de controle em rede que hoje em dia vêm sendo amplamente utilizados. Juntamente com o aparecimento dos sistemas de controle em rede, novos problemas surgiram sendo um deles o atraso de transporte nas comunicações dos sensores/atuadores/controladores e as conseqüências relacionadas a este fator. Este trabalho tem por objetivo contextualizar sistemas de controle em rede no que concerne novas metodologias de sistemas de controle, escalonamento e apresentar as influências causadas pela comunicação em redes Foundation Fieldbus no desempenho de sistemas de controle. / The development and dissemination of network protocols, the arising of ASIC chip and price drops in silicon (these two last factors allow sensors and actuators be equipped with network interfaces and thus become independent nodes in a real-time control network), make the development of Networked Control Systems possible, which became widely used. New issues - such as an increase in the communication delay among distributed sensors, controller, and actuators have to be handled by designers when developing networked control systems in order to ensure that stability and other usual control performance requirements are met. In this work, the timing behavior of a networked control developed using a Foundation Fieldbus-based network is studied and in particular the impact that communication parameters as jitter, macrocycle, and message scheduling have on control performance metrics like overshoot and settling time are evaluated both theoretically as well as experimentally.