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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the 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.
51

Potlačení nežádoucí variability ve fMRI datech při analýze pomocí psychofyziologických interakcí / Undesirable variability suppression in fMRI data during psychophysiological interactions analysis

Kojan, Martin January 2012 (has links)
The objective of the thesis is to get familiar with the method of psychophysiological interactions and its common inplementation. It is explaining the usual methods of removing disruptive signals from the data processed in correlation analysis and presents the possibility of their implementation. In the practical part it is focused on cerating suggested program and its testing on the real data sets.
52

Rozpoznávání hudebních záznamů / Recognition of musical recordings

Masár, Igor January 2013 (has links)
This thesis analyzes the specific audio signal-music. It describes the basic methods of analysis of musical signals. The following are mentioned the most common music file formats and the possibility of cross transfer. There are explained terms of music theory, which are also present in this work. They are described and created three ways of detecting melody. It is selected optimal algorithm based on the successful detection of the reference melodies recordings. User interface is created in MATLAB GUI allows recognition of recordings. This interface is tested on few melodies.
53

Variabilités hydro-climatiques multi-décennales à pluri-séculaires en Arctique-subarctique depuis 2000 ans / Multi-decadal to multi-secular hydroclimatic variability in the Arctic-subarctic since 2000 years

Nicolle, Marie 25 June 2018 (has links)
L’augmentation globale des températures au cours de la période 1850-2012 n’est pas uniforme à l’échelle du globe et l’Arctique se réchauffe deux fois plus que la moyenne. Cependant, la couverture temporelle trop courte des données instrumentales rend difficile la distinction entre la variabilité climatique naturelle et celle liée au forçage anthropique. L’étude de la variabilité climatique « exempte » de l’influence humaine est alors réalisée à partir de données proxies indirectes provenant d’archives paléoclimatiques continentales et marines. Dans la région Arctique-subarctique, les enregistrements disponibles à haute résolution sur les derniers 2000 ans ont été centralisé dans la base de données PAGES Arctic 2k. Les objectifs de ces travaux sont l’amélioration de la caractérisation et de l’interprétation de la variabilité climatique sur les derniers 2000 ans, en allant plus loin que la tendance millénaire et les périodes climatiques majeures mais aussi en s'intéressant au rôle et l’expression spatiale de la variabilité interne du système climatique. Cette thèse s'appuie sur la base de données PAGES Arctic 2k permettant l'étude des variations de températures dans la région Arctique-subarctique mais aussi d'une nouvelle base de données permettant de reconstruire les variations hydroclimatiques (précipitations et humidité) dans la région et créée lors de cette étude. L'utilisation de méthodes d'analyse du signal climatique sur des enregistrements régionaux calculés à partir de ces deux bases de données a permis de mettre en évidence une variabilité climatique dans la région Arctique-subarctique s’exprimant depuis les échelles multi-décennales à millénaire. En particulier, les variabilités multi-décennales sont en lien avec la variabilité interne du système climatique. Les variations hydroclimatiques et de températures s'exprimant aux échelles multi-décennales dans la région sont en effet caractérisées par des fréquences spécifiques aux oscillations climatiques régionales (oscillation Atlantique Nord et oscillation Pacifique décennale), en particulier sur les derniers 200 ans. Les travaux réalisés sur la base de données de températures et la réflexion autour de la création et l’exploitation de la base de données hydroclimatiques ont également conduit à la définition d’une méthodologie de travail avec une base de données paléoclimatiques, depuis sa construction jusque la définition de ses limites, notamment en termes de représentativité spatiale des séries contenues dans la base de données et de l'assimilation de données avec des saisonnalités différentes. / The temperature increase during the 1850-2012 period is not uniform globally and the Arctic is warming twice as much as the average. However, the short time coverage of instrumental data makes it difficult to distinguish natural climate variability and anthropogenic forcing. The study of climatic variability "free" of human influence requires the use of proxies data measured in continental and marine palaeoclimatic archives. In the Arctic-subarctic region, high resolution records have been centralized in the Arctic 2k PAGES database. The objectives of this work are to improve the characterization and interpretation of climatic variability over the last 2000 years, going beyond the millennial trend and the major climatic periods, but also by focusing on the role and spatial expression of the internal variability of the climate system. This thesis is based on the Arctic 2k PAGES database, which allows the study of temperature variations in the Arctic-subarctic region, as well as a new database to reconstruct hydroclimatic variations (precipitation and humidity) in the region and created during this study. The use of climate signal analysis methods on regional records calculated from these two databases has highlighted climate variability in the Arctic-subarctic region from the multi-decadal to millennial scales.In particular, multi-decadal variability is related to the internal variability of the climate system. The hydroclimatic and temperature variations expressed at multi-decadal scales in the region are characterized by frequencies specific to regional climate oscillations (North Atlantic oscillation and decadal Pacific oscillation), particularly over the last 200 years. The work done on the temperature database and the reflection on the creation and exploitation of the hydroclimatic database have also led to the definition of a working methodology with a palaeoclimatic database, from its construction to the definition of its limits, in particular in terms of the spatial representability of the series contained in the database and the assimilation of data with different seasonings.
54

Pre-processing and Feature Extraction Methods for Smart Biomedical Signal Monitoring : Algorithms and Applications

Chahid, Abderrazak 11 1900 (has links)
Human health is monitored through several physiological measurements such as heart rate, blood pressure, brain activity, etc. These measurements are taken at predefined points in the body and recorded as temporal signals or colorful images for diagnosis purposes. During the diagnosis, physicians analyze these recordings, sometimes visually, to make treatment decisions. These recordings are usually contaminated with noise caused by different factors such as physiological artifacts or electronic noises of the used electrodes/instruments. Therefore, the pre-processing of these signals and images becomes a crucial need to provide clinicians with useful information to make the right decisions. This Ph.D. work proposes and discusses different biomedical signal processing algorithms and their applications. It develops novel signal/image pre-processing algorithms, based on the Semi-Classical Signal Analysis method (SCSA), to enhance the quality of biomedical signals and images. The SCSA method is based on the decomposition of the input signal or image, using the squared eigenfunctions of a Semi-Classical Schrodinger operator. This approach shows great potential in denoising, and residual water-peak suppression for Magnetic Resonance Spectroscopy (MRS) signals compared to the existing methods. In addition, it shows very promising noise removal, particularly from pulse-shaped signals and from Magnetic Resonance (MR) images. In clinical practice, extracting informative characteristics or features from these pre-processed recordings is very important for advanced analysis and diagnosis. Therefore, new features and proposed are extracted based on the SCSA and fed to machine learning models for smart biomedical diagnosis such as predicting epileptic spikes in Magnetoencephalography (MEG). Moreover, a new Quantization-based Position Weight Matrix (QuPWM) feature extraction method is proposed for other biomedical classifications, such as predicting true Poly(A) regions in a DNA sequence, multiple hand gesture prediction. These features can be used to understand different complex systems, such as hand gesture/motion mechanism and help in the smart decision-making process. Finally, combining such features with reinforcement learning models will undoubtedly help automate the diagnoses and enhance the decision-making, which will accelerate the digitization of different industrial sectors. For instance, these features can help to study and understand fish growth in an End-To-End system for aquaculture environments. Precisely, this application’s preliminary results show very encouraging insights in optimally controlling the feeding while preserving the desired growth profile.
55

DC-DC power converters with multiple outputs

Sabbarapu, Bharath Kumar 08 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This study presents a novel converter configuration that is related to the area DC-DC power converters. To begin with, a brief introduction is given by stating the importance of power electronics. Different types of converters, their operating principles and several new topologies that are being proposed over the years, to suit a particular application with specific advantages are listed in detail. In addition, pro- cedure for performing small signal analysis, which is one among the several averaging techniques is summarized in the first chapter. In the second chapter, small signal modeling is carried out on the single input dual output DC-DC buck converter. This analysis is performed to get a clear un- derstanding on the dynamics of this novel configuration. Routh stability criterion is also applied on this converter topology to determine the limiting conditions for operating the converter in its stability. Third chapter proposes the single input multiple output DC-DC synchronous buck converter. It’s operation, implementation and design are studied in detail. In further, small signal analysis is performed on this topology to determine the transfer function. In the following chapter, results obtained on comparison of a losses between the conventional and traditional topologies are presented in detail. In addition, results achieved during the analysis performed in the previous chapter are displayed. In the end, advantages and its highlights of this novel configuration proposed in this study is summarized. Future course of actions to be done, in bringing this configuration in to practice are discussed as well.
56

Bi-tapered Fiber Sensor Using a Supercontinuum Light Source for a Broad Spectral Range

Garcia Mina, Diego Felipe 24 May 2017 (has links)
No description available.
57

Analysis and design of a 500 kHz series resonant inverter for induction heating applications

Grajales, Liliana 06 June 2008 (has links)
The steady state model and analysis of a phase-shift controlled series resonant inverter (PSC-SRl) is presented. This steady state model includes the evaluation of the zero-voltage switching (ZVS) condition and the determination of the ZVS operating region. Based upon this analysis a frequency control strategy that minimizes circulating energies is proposed. Also, a methodology to design the power stage components, and to predict the duty ratio and the operating frequency range is presented using a PSC-SRl design example operating at 500 kHz and 10 kW. In addition, a novel and simple frequency control circuit that implements the proposed frequency control strategy is provided. Besides, the analysis of the PSC-SRl complete power stage and two control-loop system (frequency control and duty ratio control) is given. Furthermore, the small-signal model and the compensation schemes for each of the control loops is presented. The analytical predictions are compared with experimental data measured from a 500 kHz, 10 kW laboratory prototype and conclusions are drawn. / Ph. D.
58

Small-signal Analysis and Design of Constant-on-time V2 Control for Ceramic Caps

Tian, Shuilin 18 May 2012 (has links)
Recently, constant-on-time V2 control is more and more popular in industry products due to features of high light load efficiency, simple implementation and fast transient response. In many applications such as cell phone, camera, and other portable devices, low-ESR capacitors such as ceramic caps are preferred due to small size and small output voltage ripple requirement. However, for the converters with ceramic caps, the conventional V2 control suffers from the sub-harmonic oscillation due to the lagging phase of the capacitor voltage ripple relative to the inductor current ripple. Two solutions to eliminate sub-harmonic oscillations are discussed in [39] and the small-signal models are also derived based on time-domain describing function. However, the characteristic of constant-on-time V2 with external ramp is not fully understood and no explicit design guideline for the external ramp is provided. For digital constant on-time V2 control, the high resolution PWM can be eliminated due to constant on-time modulation scheme and direct output voltage feedback [43]. However, the external ramp design is not only related to the amplitude of the limit-cycle oscillation, but also very important to the stability of the system. The previous analysis is not thorough since numerical solution is used. The primary objective of this work is to gain better understanding of the small-signal characteristic for analog and digital constant-on-time V2 with ramp compensations, and provide the design guideline based on the factorized small-signal model. First, constant on-time current-mode control and constant on-time V2 control are reviewed. Generally speaking, constant-on-time current mode control does not have stability issues. However, for constant-on-time V2 control with ceramic caps, sub-harmonic oscillation occurs due to the lagging phase of the capacitor voltage ripple. External ramp compensation and current ramp compensation are two solutions to solve the problem. Previous equivalent circuit model extended by Ray Ridley's sample-and-hold concept is not applicable since it fails to consider the influence of the capacitor voltage ripple. The model proposed in [39] successfully considers the influence from the capacitor voltage ripple by using time-domain describing function method. However, the characteristic of constant-on-time V2 with external ramp is not fully understood. Therefore, more research focusing on the analysis is needed to gain better understanding of the characteristic and provide the design guideline for the ramp compensations. After that, the small-signal model and design of analog constant on-time V2 control is investigated and discussed. The small-signal models are factorized and pole-zero movements are identified. It is found that with increasing the external ramp, two pairs of double poles first move toward each other at half of switching frequency, after meeting at the key point, the two double poles separate, one pair moves to a lower frequency and the other moves to a higher frequency while keeping the quality factor equal to each other. For output impedance, with increasing the external ramp, the low frequency magnitude also increases. The recommended external ramp is around two times the magnitude at the key point K. When Duty cycle is larger, the damping performance is not good with only external ramp compensation, unless very high switching frequency is used. With current ramp compensation, it is recommended to design the current ramp so that the quality factor of the double pole is around 1. With current ramp compensation, the damping can be well controlled regardless of the circuit parameters. Next, the small-signal analysis and design strategy is also extended to digital constant on-time V2 control structure which is proposed in [43]. It is found that the scenario is very similar as analog constant on-time V2 control. The external ramp should be designed around the key point to improve the dynamic performance. The sampling effects of the output voltage require a larger external ramp to stabilize digital constant-on-time V2 control while suffers only a little bit of damping performance. One simple method for measuring control-to-output transfer functions in digital constant-on-time V2 control is presented. The experimental results verify the small-signal analysis except for the high frequency phase difference which reveals the delay effects in the circuit. Load transient experimental results prove the proposed design guideline for digital constant on-time V2 control. As a conclusion, the characteristics of analog and digital constant-on-time V2 control structures are examined and design guidelines are proposed for ramp compensations based on the factorized small-signal model. The analysis and design guideline are verified with simplis simulation and experimental results. / Master of Science
59

Multiphase flow measurement using gamma-based techniques

Arubi, Isaac Marcus Tesi January 2011 (has links)
The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves. This has led oil companies to develop smaller/marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective soluti8ons of on-line continuous multiphase flow measurement. The pattern recognition approach for clamp-on multiphase measurement employed in this research study provides one means for meeting this need. Cont/d.
60

A Complexity Analysis of Noise-like Activity in the Nervous System and its Application to Brain State Classification and Identification in Epilepsy

Serletis, Demitre 18 January 2012 (has links)
Complexity lies halfway between stochasticity and determinism, suggesting that brain activity is neither fully random nor fully predictable but lives by the rules of nonlinear high- and low-complexity dynamics. One important aspect of brain function is noise-like activity (NLA), defined as background, electrical potential fluctuations in the nervous system distinct from spiking rhythms in the foreground. The objective of this thesis was to investigate the neurodynamical complexity of NLA recorded at the cellular and local network scales in in vitro preparations of mouse and human hippocampal tissue, under healthy and epileptiform conditions. In particular, it was found that neuronal NLA arises out of the physiological contributions of gap junctions and chemical synaptic channels and is characterized by a spectrum of complexity, ranging from high- to low-complexity, that was measured using methods from nonlinear dynamical systems theory. Importantly, the complexity of background, neuronal NLA was shown to depend on the degree of cellular interconnectivity to the surrounding local network. In addition, the complexity and multifractality of NLA was further studied at the cellular and local network scales in epileptiform transitions to seizure-like events, identifying emergent low-complexity and reduced multifractality (bordering on monofractal-type dynamics) in the pathological ictal state. Finally, dual intracellular recordings of hippocampal epileptiform activity were analyzed to measure NLA synchronicity, showing evidence for increased same- and cross-frequency correlations and increased phase synchronization in the pathological ictal state. Convergence towards increased phase synchrony manifested in lower frequency regions including theta (4-10 Hz) and beta (12-30 Hz), but also in higher frequency bands (gamma, 30-80 Hz). In summary, there is evidence to suggest that background NLA captures important neurodynamical information pertinent to the classification and identification of brain state transitions in healthy and epileptiform hippocampal dynamics, using sophisticated neuroengineering analyses of these physiological signals.

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