Thesis (M.A.(Publishing)(Information Science)--University of Pretoria, 2003. / Title from opening screen (viewed 10 March, 2005). includes summary. Includes bibliographical references.

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: p. 199-206.

<p>High pressure surface discharge switches have become the subject of applied research in recent years due to their important application in pulse power systems. The purpose of this study is to gain a better understanding of the subject so that an optimum design of the switch may be achieved. The surface discharge phenomena is examined under single channel static breakdown condition to attempt to isolate individual processes involved. The multichannel switch developed by the NRC is tested with a resistive load assembly to determine the optimum operating conditions. The lifetime characteristic is also studied using a small experimental device. Finally, two models for the switch are developed to fit the observed data. </p> / Thesis / Master of Engineering (MEngr)

<p> The study of the different sleep stages of a patient using his/her recorded EEG signals falls in the area of signal classification. In general, this involves extracting from the EEG signals, a signal feature on which the classification is performed. In this thesis, we apply the techniques of signal classification to the analysis of the sleep of a patient. The feature we use is the power spectral density (PSD) matrices of a multi-channel EEG signal. This not only allows us to examine the power spectrum contents of each signal which complies with what clinical experts use in their visual judgement of EEG signals, but also allows the correlation between the multi-channel signals to be studied. To establish a metric facilitating the classification, we analyze the structure as well as exploit the specific geometric properties of the space of PSD matrices. Specifically, we study this space from the viewpoint of Riemannian manifolds. We apply a Riemannian metric and, with the aid of fibre bundle theory, develop intrinsic (geodesic) distance measures for the PSD matrix manifold. To utilize such new distance measures effectively for EEG signal classification, we need to find a suitable weighting matrix for the PSD matrices so that the distances between similar features are minimized while those between dissimilar features are maximized. A closed form expression for this weighting matrix is obtained by solving an equivalent convex optimization problem. The effectiveness of using these novel weighted distance measures is verified by applying them to the sleep pattern classification of a collection of recorded EEG signals using the k-nearest neighbor decision algorithm with excellent results. </p> / Thesis / Doctor of Philosophy (PhD)

Pulse oximetry is used to measure heart rate (HR) and arterial oxygen saturation (SpO2) from photoplethysmographic (PPG) waveforms. PPG waveforms are highly sensitive to motion artifact (MA), limiting the implementation of pulse oximetry in mobile physiological monitoring using wearable devices. Previous studies have shown that multichannel pulse oximetry can successfully acquire diverse signal information during simple, repetitive motion, thus leading to differences in motion tolerance across channels. In this study, we introduce a multichannel forehead-mounted pulse oximeter and investigate the performance of this novel sensor under a variety of intense motion artifacts. We have developed a multichannel template-matching algorithm that chooses the channel with the least amount of motion artifact to calculate HR and SpO2 every 2 seconds. We show that for a wide variety of random motion, channels respond differently to motion, and the multichannel estimate outperforms single channel estimates in terms of motion tolerance, signal quality, and HR and SpO2 error. Based on 31 data sets of PPG waveforms corrupted by random motion, the mean relative HR error was decreased by an average of 5.6 bpm when the multichannel-switching algorithm was compared to the worst performing channel. The percentage of HR measurements with absolute errors ≤ 5 bpm during motion increased by an average of 27.8 % when the multichannel-switching algorithm was compared to the worst performing channel. Similarly, the mean relative SpO2 error was decreased by an average of 4.3 % during motion when the multichannel-switching algorithm was compared to each individual channel. The percentage of SpO2 measurements with absolute error ≤ 3 % during motion increased by an average of 40.7 % when the multichannel-switching algorithm was compared to the worst performing channel. Implementation of this multichannel algorithm in a wearable device will decrease dropouts in HR and SpO2 measurements during motion. Additionally, the differences in motion frequency introduced across channels observed in this study shows precedence for future multichannel-based algorithms that make pulse oximetry measurements more robust during a greater variety of intense motion.

Bakgrund I takt med en ökad digitalisering sker handel idag inte endast i fysiska butiker. Fler och fler klädföretag använder idag e-handel som försäljningskanal för att sälja sina produkter, samtidigt som efterfrågan från konsumenter är i ständig förändring. Trycket på att tillgodose kundernas behov och skapa kundnöjdhet sätter press på företagsledningar att använda flera kanaler, känt som multikanalförsäljning. Som följd har begreppet multichannel customer management vuxit fram som lyfter vikten av att utvärdera sina kanaler för att i sin tur kunna allokera resurser till respektive kanal. Syfte Syftet med studien är att inom klädbranschen undersöka hur ett antal nyckelfaktorer påverkar kundnöjdheten inom fysiska försäljningskanaler respektive e-handelskanaler. Vidare ämnar studien förklara vilka av nyckelfaktorerna företag för respektive försäljningskanal bör fokusera på i syfte att uppnå kundnöjdhet och i sin tur kundlojalitet. Genomförande Med ett realistiskt perspektiv, en deduktiv ansats och en kvantitativ metod har 8 hypoteser tagits fram utifrån befintlig forskning. Den empiriska undersökningen bestod av en enkät som delades ut på Linköpings universitet och besvarades av 224 studenter inom Generation Y. Vidare användes programmet SPSS för att genomföra en statistisk analys av insamlad primärdata. Slutsats För att uppnå kundnöjdhet och i sin tur kundlojalitet visar studiens resultat att företag, för sin fysiska försäljningskanal, bör fokusera på faktorerna service, tillgänglighet, tid och säkerhet. Studiens resultat visar även att företag för sin e-handelskanal bör fokusera på produktgaranti, tid och säkerhet för att uppnå kundnöjdhet och kundlojalitet. / Background: Companies today are, due to an increased digitization, forced to use more than traditional stores to reach out to their customers. More and more retailers are now using online stores to meet an even broader market and to attain customer satisfaction. Using more than one channel has become known as multichannel retailing, from which a concept known as multichannel customer management has started to grow. The concept says that as the number of channels used increase, companies need to evaluate their channels in order to allocate resources to each one. Purpose: The purpose with the study is to examine how a couple of key factors, in the apparel industry, affect customer satisfaction in traditional and online channels. The study aims to explain which one of these factors each channel should focus on to achieve customer satisfaction and customer loyalty. Completion: With a realistic perspective, deductive approach and quantitative method 8 hypothesis have been tested. The empirical study was conducted by handing out a survey on Linköping University and in total 224 respondents within Generation Y answered. To analyze the collected data, the statistical software SPSS was used. Conclusion: In order to accomplish customer satisfaction and customer loyalty the study shows that companies, for their traditional stores, should focus on service, accessibility, time and safety. The results of the study shows that companies, for their online stores, should focus on product guarantee, time and safety.

No description available.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / In this paper, by using computer simulations, the interference of channel data in the SDM telemetry system is investigated, the performance of the copy demultiplexing is examined, and finally the selection rule of Walsh functions is recommended.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Neste documento apresentamos uma cifra multicanal inspirada nas técnicas de telecomunicações de espalhamento espectral (Spread Spectrum), ou como também conhecido, difusão espectral, para prevenir escuta em uma rede de computadores TCP/IP. Mostramos que dividindo um texto-ilegível ciphertext em blocos de tamanho fixo e transmitindo-os aleatoriamente através de diversos canais estabelecidos entre os agentes (transmissor - receptor) é possível aumentar a complexidade da criptanálise por um suposto adversário não autorizado que esteja escutando a comunicação, dessa forma aumentando relativamente a segurança. Mostramos teoricamente que o tempo de quebra da cifra multicanal cresce em ordem fatorial ou exponencial em função do número de canais utilizados na comunicação. Além disso, adaptado a um esquema de difusão binária herdado do AES (Advanced Encryption Standard) é possível incrementar a segurança da cifra multicanal para maior resiliência contra a criptanálise diferencial. / In this work we present a multichannel cipher inspired on telecommunications Spread Spectrum techniques to prevent eavesdropping in a TCP/IP network. We show that splitting any ciphertext into fixed size blocks and sending them randomly through multiple channels established between the agents (transmitter and receiver) it is possible to increase the complexity of cryptanalysis by a supposed not authorized adversary that might be eavesdropping the communication, in this way, relatively increasing the security. We show theoretically that the brake time of multichannel cipher grows in factorial or exponential order, in function of the number of channel used in the communication. Moreover adapted to binary spread scheme inherited from AES (Advanced Encryption Standard) it is possible to increase the cipher security for more resilience against differential cryptanalysis.