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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 341 to 348 of 348 (0.112 seconds)| 341 |
MRI Integrated Systems for Multimodal ImagingRanajay Mandal (9750932) 10 December 2021 (has links)
In recent years, development of various imaging, recording and stimulation tools are rapidly advancing our knowledge of the human anatomy and its underlying interconnections. As a truly non-invasive tool, Magnetic Resonance Imaging (MRI), is creating new opportunities to understand large scale biological processes with a fine detail. Furthermore, novel materials and microfabrication techniques are allowing researchers to develop tools that record bio-signal or modulate complex physiology with high temporal precision. However, these tools, when used individually can elucidate only a partial view of the human body and the brain. There is a growing need in both the research and clinical community to find ways to perform these modalities together and visualize biological systems across a vast range of spatiotemporal scale. However, severe methodological challenges act as bottlenecks for any such multimodal integration.<br><div><br></div><div>To address this critical need, I have designed an MRI-safe platform for high-fidelity bio-signal recording and electrical stimulation during concurrent MRI imaging. Central to this system are novel miniaturized microelectronic devices, that operate wirelessly in synchrony with MRI scans. The system leverages surplus functionalities of a conventional scanner to integrate with the imaging system and provide a simple and inexpensive solution towards multimodal imaging. This work also describes a systematic approach for development and evaluation of this plug-and-play system through in-vivo experiments in animal models. The clinical relevance of the multimodal imaging platform was further showcased through a study on the mechanism of SUDEP (Sudden death in epilepsy), a terminal complication associated with epilepsy. With future refinements, I expect this platform will provide affordable, accessible, and reliable solutions for multimodal imaging in animals and humans, creating unique opportunities for basic scientific research and clinical diagnosis.<br></div>
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Vliv přenosových parametrů na spotřebu elektrické energie Zigbee zařízení / Impact of Communication Parameters on Energy Consumption of Zigbee DevicesPopelka, Jan January 2013 (has links)
This thesis deals with the energy research and design a simple wireless sensor networks. The data modules with ZigBee wireless communication technology. The main feature of wireless sensor networks is the minimal energy devices at low cost and maximum data reliability. Furthermore, the work describes firmware for communicating nodes with the ability to change parameters of data transmission and thus affect the energy consumption node. Calculations of energy consumption, compared with measured results and discharge characteristics of the battery packs are included in the final chapters of this work.
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Vliv přenosových parametrů na spotřebu elektrické energie Zigbee zařízení / Impact of Communication Parameters on Energy Consumption of Zigbee DevicesPopelka, Jan January 2013 (has links)
This thesis deals with the energy research and design a simple wireless sensor networks. The data modules with ZigBee wireless communication technology. The main feature of wireless sensor networks is the minimal energy devices at low cost and maximum data reliability. Furthermore, the work describes firmware for communicating nodes with the ability to change parameters of data transmission and thus affect the energy consumption node. Calculations of energy consumption, compared with the measured results, the discharge characteristics of the battery packs and lifetime broadcasting node is contained in the final chapters of this work.
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Design of Intelligent Internet of Things and Internet of Bodies Sensor NodesShitij Tushar Avlani (11037774) 23 July 2021 (has links)
<div>Energy-efficient communication has remained the primary bottleneck in achieving fully energy-autonomous IoT nodes. Several scenarios including In-Sensor-Analytics (ISA), Collaborative Intelligence (CI) and Context-Aware-Switching (CAS) of the cluster-head during CI have been explored to trade-off the energies required for communication and computation in a wireless sensor network deployed in a mesh for multi-sensor measurement. A real-time co-optimization algorithm was developed for minimizing the energy consumption in the network for maximizing the overall battery lifetime of individual nodes.</div><div><br></div><div>The difficulty of achieving the design goals of lifetime, information accuracy, transmission distance, and cost, using traditional battery powered devices has driven significant research in energy-harvested wireless sensor nodes. This challenge is further amplified by the inherent power intensive nature of long-range communication when sensor networks are required to span vast areas such as agricultural fields and remote terrain. Solar power is a common energy source is wireless sensor nodes, however, it is not reliable due to fluctuations in power stemming from the changing seasons and weather conditions. This paper tackles these issues by presenting a perpetually-powered, energy-harvesting sensor node which utilizes a minimally sized solar cell and is capable of long range communication by dynamically co-optimizing energy consumption and information transfer, termed as Energy-Information Dynamic Co-Optimization (EICO). This energy-information intelligence is achieved by adaptive duty cycling of information transfer based on the total amount of energy available from the harvester and charge storage element to optimize the energy consumption of the sensor node, while employing event driven communication to minimize loss of information. We show results of continuous monitoring across 1Km without replacing the battery and maintaining an information accuracy of at least 95%.</div><div><br></div><div>Decades of continuous scaling in semiconductor technology has resulted in a drastic reduction in the cost and size of unit computing. This has enabled the design and development of small form factor wearable devices which communicate with each other to form a network around the body, commonly known as the Wireless Body Area Network (WBAN). These devices have found significant application for medical purposes such as reading surface bio-potential signals for monitoring, diagnosis, and therapy. One such device for the management of oropharyngeal swallowing disorders is described in this thesis. Radio wave transmission over air is the commonly used method of communication among these devices, but in recent years Human Body Communication has shown great promise to replace wireless communication for information exchange in a WBAN. However, there are very few studies in literature, that systematically study the channel loss of capacitive HBC for <i>wearable devices</i> over a wide frequency range with different terminations at the receiver, partly due to the need for <i>miniaturized wearable devices</i> for an accurate study. This thesis also measures and explores the channel loss of capacitive HBC from 100KHz to 1GHz for both high-impedance and 50Ohm terminations using wearable, battery powered devices; which is mandatory for accurate measurement of the HBC channel-loss, due to ground coupling effects. The measured results provide a consistent wearable, wide-frequency HBC channel loss data and could serve as a backbone for the emerging field of HBC by aiding in the selection of an appropriate operation frequency and termination.</div><div><br></div><div>Lastly, the power and security benefits of human body communication is demonstrated by extending it to animals (animal body communication). A sub-inch^3, custom-designed sensor node is built using off the shelf components which is capable of sensing and transmitting biopotential signals, through the body of the rat at significantly lower powers compared to traditional wireless transmissions. In-vivo experimental analysis proves that ABC successfully transmits acquired electrocardiogram (EKG) signals through the body with correlation accuracy >99% when compared to traditional wireless communication modalities, with a 50x reduction in power consumption.</div>
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[en] 3-D RAY TRACING TECHNIQUES FOR INDOOR AND OUTDOOR FIELD CALCULATIONS / [es] TÉCNICAS DE TRAZADO DE RAYOS EN TRES DIMENSIONES PARA CÁLCULO DE CAMPOS EN AMBIENTES INTERIORES Y EXTERIORES / [pt] TÉCNICAS DE TRAÇADO DE RAIOS EM TRÊS DIMENSÕES PARA CÁLCULO DE CAMPOS EM AMBIENTES INTERIORES E EXTERIORESMARCIO EDUARDO DA COSTA RODRIGUES 01 August 2000 (has links)
[pt] O problema do cálculo de cobertura em sistemas celulares operando em regiões urbanizadas
tem sido bastante estudado por diversos autores, existindo um conjunto de métodos de
previsão amplamente testados e implementados em ferramentas computacionais. Atualmente,
com a aplicação da tecnologia celular a sistemas de transmissão de dados de faixa larga, o
foco dos estudos nesta área deslocou-se para o cálculo de cobertura em micro e picocélulas.
Este trabalho apresenta uma revisão dos principais métodos empíricos para a previsão da
propagação em sistemas micro e picocelulares. A seguir é realizado o estudo de uma técnica
mais precisa para estes cálculos, empregando traçado de raios e o rastreamento do campo
eletromagnético ao longo dos mesmos segundo a Teoria Uniforme da Difração (UTD).
É desenvolvido todo um conjunto de algoritmos para a aplicação do traçado de raios,
considerados os problemas de reflexão, refração (transmissão) e difração num cenário
tridimensional (problema vetorial). A difração é tratada a partir da generalização das
formulações assintóticas disponíveis para tratar o espalhamento por obstáculos perfeitamente
condutores.
Parte destes algoritmos, referentes aos problemas de reflexão múltipla, foi implementada em
linguagem C++
e alguns exemplos de aplicação são apresentados neste trabalho. / [en] The problem of the electromagnetic coverage in cellular
systems designed to operate in urban regions has being
massively studied by many authors, existing a set of
prediction models largely tested and implemented in
computational tools. Nowadays, with the application of the
cellular technology in broadband data transmission systems,
the focus of the research in this area has moved to the
coverage computation in micro and picocells.
This work presents a review of the main empirical methods
for the propagation prediction in micro and picocellular
systems. Following it, a study is made of a more precise
technique for these computations, employing ray tracing and
the tracking of the electromagnetic field in each point of
the ray trajectory by using the Uniform Theory of
Diffraction (UTD).
It is developed a pack of algorithms for the application of
the ray tracing techniques, to the problems of reflection,
refraction (transmission through slabs) and diffraction in
a tridimensional scene (vectorial problem). Diffraction is
dealed with by extending available asymptotic formulations
for scattering by perfectly conducting obstacles.
A portion of these algorithms, refering to the problem of
multiple reflections, has been implemented in a C++
computer code and applied herein to selected case studies. / [es] El problema del cálculo de cobertura en sistemas celulares que operan en regiones urbanizadas ha sido bastante
estudiado por diversos autores. Como resultado, existe un conjunto de métodos de previsión ampliamente
probados e implementados computacionalmente. Actualmente, con la aplicación de la tecnología celular a
sistemas de transmisión de datos de larga faja, el foco de los estudios en esta área ha pasado a ser el cálculo de
cobertura en micro e picocélulas. Este trabajo presenta una revisión de los principales métodos empíricos para la
previsión de propagación en sistemas micro e picocelulares. A seguir se estudia una técnica más precisa para
estos cálculos, que utiliza trazado de rayos y rastreamiento del campo eletromagnético según la Teoría Uniforme
de la Difracción (UTD). Se desarrolla un conjunto de algoritmos para la aplicación del trazado de rayos,
considerando los problemas de reflexión, refracción (transmisión) y difracción en un escenario tridimensional
(problema vectorial). La difracción es tratada a partir de la generalización de las formulaciones asintóticas
disponibles para tratar la dispersión por obstáculos perfectamente conductores. Una parte de estos algoritmos,
referidos a los problemas de reflexión múltiple, fueron implementada en lenguaje C++ y algunos ejemplos de
aplicación se apresentan en este trabajo.
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Design Techniques for Secure IoT Devices and NetworksMalin Priyamal Prematilake (12201746) 25 July 2023 (has links)
<p>The rapid expansion of consumer Internet-of-Things (IoT) technology across various application domains has made it one of the most sought-after and swiftly evolving technologies. IoT devices offer numerous benefits, such as enhanced security, convenience, and cost reduction. However, as these devices need access to sensitive aspects of human life to function effectively, their abuse can lead to significant financial, psychological, and physical harm. While previous studies have examined the vulnerabilities of IoT devices, insufficient research has delved into the impact and mitigation of threats to users' privacy and safety. This dissertation addresses the challenge of protecting user safety and privacy against threats posed by IoT device vulnerabilities. We first introduce a novel IWMD architecture, which serves as the last line of defense against unsafe operations of Implantable and Wearable Medical Devices (IWMDs). We demonstrate the architecture's effectiveness through a prototype artificial pancreas. Subsequent chapters emphasize the safety and privacy of smart home device users. First, we propose a unique device activity-based categorization and learning approach for network traffic analysis. Utilizing this technology, we present a new smart home security framework and a device type identification mechanism to enhance transparency and access control in smart home device communication. Lastly, we propose a novel traffic shaping technique that hinders adversaries from discerning user activities through traffic analysis. Experiments conducted on commercially available IoT devices confirm that our solutions effectively address these issues with minimal overhead.</p>
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Channel Probing for an Indoor Wireless Communications ChannelHunter, Brandon 13 March 2003 (has links) (PDF)
The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Návrh vnitřního optického spoje / Indoor optical wireless link designKaňa, Leoš January 2011 (has links)
In last years phenomena of wireless communication technologies became a primary interest of big development laboratories whole world. Domain of point to point links which are realized by laser technology with narrow beam divergence and very sensitive photo-detectors is ordinarily used these days. This trend of using light waves as carrier medium turned interests of scientist to the sphere of wide area networks which is domain of wi-fi radio technologies. One of new trends in this sphere is also in-door free space optics. With expansion which leads to using LED's in everyday applications and with technological progress of last years, also grows tendency of most effective utilization of LED systems. The result of this effort is thought which considerate LED as source of artificial lighting and source of carrier medium for modulated signal. This kind of device must fulfill hygienic standards for illumination and also must be able to work with high frequency by which is signal modulated. These systems can provide links with sufficient capacity in order of hundred megabits.
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