In this study, a mathematical model is developed for investigating the discrete sound propagation in viscoelastic medium to identify its viscoelastic properties. The outcome of the model suggests that pulse repetition frequency is a very important parameter for the determination of relaxation time. Adjusting the order of magnitude of the pulse repetition frequency, the corresponding relaxation time which has similar magnitude with pulse repetition frequency is filtered while the others in the spectrum are discarded. Discrete relaxation spectrum can be obtained by changing the magnitude of the pulse repetition frequency. Therefore, the model enables to characterize the relaxation times by ultrasonic measurements.

Recentemente observou-se experimentalmente, Johnson et al. (2010), que fatias organotípicas corticais de rato são capazes de completar padrões espaço-temporais, após serem treinadas. Embora se especule que mecanismos de plasticidade sináptica e homeostática estejam por trás do fenômeno, ainda não existe nenhuma explicação detalhada sobre o assunto. Com o intuito de propor uma explicação clara e consistente para os mecanismos que permeiam a resposta da rede aos estímulos como um todo, nos propomos a estudar este fenômeno por meio de uma rede de neurônios de integração-e-disparo dotada de mecanismos de homeostase intrínseca e de plasticidade sináptica dependente de disparos. O sistema construído foi explorado, de modo a determinar em que condições a rede poderia comportar-se como o sistema real, e treinado de forma similar `a realizada experimentalmente por Johnson et al. (2010). / Recently it has been observed experimentally, Johnson et al. (2010), that organotypic cortical slices of rat are capable of completing spatio-temporal patterns after training. Although it is speculated that synaptic and homeostatic plasticity may have an important role in this phenomenon, there is still no detailed explanation about this subject. In order to propose a clear and consistent explanation for the mechanisms that underlie the network response to stimuli as a whole, we propose to study this phenomenon through a network of integrate-and-fire neurons endowed with intrinsic homeostasis and spike-timing dependent plasticity mechanisms. The constructed system was explored, aiming to determine in which conditions the network could behave as the real system, and trained in a way similar as the experimental one done by Johnson et al. (2010).

Recentemente observou-se experimentalmente, Johnson et al. (2010), que fatias organotípicas corticais de rato são capazes de completar padrões espaço-temporais, após serem treinadas. Embora se especule que mecanismos de plasticidade sináptica e homeostática estejam por trás do fenômeno, ainda não existe nenhuma explicação detalhada sobre o assunto. Com o intuito de propor uma explicação clara e consistente para os mecanismos que permeiam a resposta da rede aos estímulos como um todo, nos propomos a estudar este fenômeno por meio de uma rede de neurônios de integração-e-disparo dotada de mecanismos de homeostase intrínseca e de plasticidade sináptica dependente de disparos. O sistema construído foi explorado, de modo a determinar em que condições a rede poderia comportar-se como o sistema real, e treinado de forma similar `a realizada experimentalmente por Johnson et al. (2010). / Recently it has been observed experimentally, Johnson et al. (2010), that organotypic cortical slices of rat are capable of completing spatio-temporal patterns after training. Although it is speculated that synaptic and homeostatic plasticity may have an important role in this phenomenon, there is still no detailed explanation about this subject. In order to propose a clear and consistent explanation for the mechanisms that underlie the network response to stimuli as a whole, we propose to study this phenomenon through a network of integrate-and-fire neurons endowed with intrinsic homeostasis and spike-timing dependent plasticity mechanisms. The constructed system was explored, aiming to determine in which conditions the network could behave as the real system, and trained in a way similar as the experimental one done by Johnson et al. (2010).

This Master´s thesis focuses on design and implementation of programmable attenuator. The main aim of this thesis is to create an electronical device that provide continuous setting of attenuation value in the range between 0–150 dB. Setting a value from the range can be performed using buttons and set values are shown on display. For this thesis an attenuator with working frequency between 0–6 GHz was chosen and four–layer printed circuit board was designed. As a result the device is fitted with an 8bit microcontroller ATmega328P–PU using five 6bit digital attenuators connected in series with manual and program settings of attenuation from 0–157,5 dB with step of 0,5 dB. Data are shown on a build–in display. The application for remote settings and value reading over integrated USB (Universal Serial Bus) interface, was created in C#. In conclusion of this thesis there is a measurement evaluation of attenuation measurement performed on the device.

The master‘s thesis is focused on data transfer over power lines. The influence of connected devices on data signal is studied. In this thesis, you can find the descriptions of PLC technology characteristics, sources of signal interruption and, mainly, the method of modelling the PLC channels as a multipath signal propagation environment is thoroughly discussed. There are models of PLC channels using this method projected in Simulink. The analysis of the influence of connected devices to bit error rate of a signal is processed. The devices are modelled by connected impedance.

Noise pollution from aircraft is an ever-increasing issue in urban areas. Venting exhaust over body panels could reduce perceived sound pressure levels (SPL) by absorption or redirection. This paper investigates the farield spectra and sound propagation of a flat panel held near an axis-symmetric supersonic jet. In contrast to typical radial acquisition, Overall sound pressure level (OASPL) contours are constructed from a 9 by 23 cartesian acquisition gird, spaced equidistantly at 3.67 Jet Diameters (Dj). Three panel configurations each at three nozzle pressure ratios (NPR) are discussed. Additionally, a source finding algorithm is developed and shows source locations by frequency. Panel presence for nozzle design conditions result in a near flat increase in SPL across the acquired spectrum, while over and under expanded nozzle cases show the propagation of resonant modes.

Made available in DSpace on 2016-04-04T18:31:30Z (GMT). No. of bitstreams: 1 RINA GRACIELA RONDON GONZALEZ.pdf: 1534454 bytes, checksum: 58f56e565eb9e4082c5b978ceee457f4 (MD5) Previous issue date: 2009-12-18 / Due to the increasing demand for services related to wireless networks, such as video, voice and video conferencing and to the concern of telecommunications companies to meet this demand efficiently, the planning of a wireless link becomes very important. Since the propagation of a signal over a wireless network is not driven, it can suffer attenuation caused by obstacles in the medium during its transfer from the transmitting equipment to the receiver, varying the signal strength of the transmission in each area covered. For this reason, in order to plan a wireless network, the characteristics of the environment and infrastructure through which the signal will travel, needs to be taken into account, so it is possible to get the real value of the received power at each required point. Furthermore, since the prediction of the signal?s attenuation in different places, taking into account the impact caused by each mentioned factor in its degradation, can be considered a complex process, it is necessary to use a model that not only considers the characteristics of the medium but also relates these factors in a simple manner allowing to measure the signal?s attenuation caused by the barriers founded in the environment. The Shadowing Signal Propagation model allows the characterization of the attenuation caused by the environment through the ? parameter present in this model. On the other hand, the Fuzzy Logic provides a form of approximate reasoning that allows the treatment of problems with incomplete, vague and imprecise information. Also, it offers a simple way to obtain a possible solution for a problem using the heuristic knowledge about a particular situation. In this way, the Fuzzy Logic can be an useful tool for calculating the ? parameter of the Shadowing Signal Propagation model, making possible to obtain ? values that characterize the attenuation of the environment in study. In this context, this work focuses on the analysis of signal?s attenuation in indoor environments using fuzzy logic. / Devido ? crescente demanda dos servi?os sobre redes sem fio, como v?deo, voz e v?deo confer?ncia e ? preocupa??o das companhias de telecomunica??es em atender esta demanda de forma eficiente, torna-se de fundamental import?ncia o planejamento de um enlace sem fio. Dado que a propaga??o de um sinal em uma rede sem fio n?o ? guiada, esta pode sofrer atenua??o causada pelos obst?culos encontrados no meio durante o seu percurso desde o equipamento transmissor at? o receptor, variando a pot?ncia do sinal da transmiss?o em cada ambiente percorrido. Por este motivo, para fazer o planejamento da rede ? necess?rio que sejam consideradas as caracter?sticas do ambiente e infra-estrutura por onde o sinal vai trafegar de modo que seja poss?vel obter o valor real da pot?ncia recebida em cada ponto do trajeto. Uma vez que a predi??o da atenua??o do sinal em diferentes ambientes, contemplando o impacto relacionado a cada fator que contribui com sua degrada??o, constitui-se em processo bastante complexo, existe a necessidade de utiliza??o de um modelo que al?m de contemplar as caracter?sticas do meio possa relacionar os fatores acima mencionados de uma forma simples de modo a permitir a determina??o da atenua??o do sinal causada pelas barreiras localizadas no meio. O Modelo de Propaga??o do Sinal de Shadowing permite caracterizar a atenua??o gerada pelo meio, atrav?s do par?metro ? presente na equa??o deste modelo. Por outro lado, a L?gica Nebulosa apresenta uma forma de racioc?nio aproximado que permite o tratamento de problemas com informa??es incompletas, vagas e imprecisas. Tamb?m, oferece uma forma simples de inferir uma poss?vel solu??o para um problema usando o conhecimento heur?stico sobre determinada situa??o. Neste sentido, a L?gica Nebulosa resulta em uma ferramenta ?til para o c?lculo do par?metro ? do Modelo de Propaga??o do Sinal de Shadowing posibilitando a obten??o de valores de ? que caracterizem com maior especifica??o a atenua??o do ambiente em estudo. Neste contexto, o presente trabalho trata da an?lise da atenua??o do sinal em ambientes indoor usando l?gica nebulosa.

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Ortsbasierte Dienste erfreuen sich in den letzten Jahren starker Beliebtheit. Für deren Umsetzung sind sog. Lokalisierungsdienste notwendig, welche eine Ortung von Mobilgeräten erlauben. Das GPS stellt den wohl populärsten Lokalisierungsdienst dar, ist jedoch innerhalb von Gebäuden nur sehr beschränkt einsetzbar. In der Vergangenheit wurden deshalb Methoden vorgeschlagen, die zur Positionsbestimmung auf die Messung der Empfangsfeldstärke von WLAN-Aussendungen zurückgreifen. Im Rahmen der Diplomarbeit soll untersucht werden, ob sich ebenfalls eine Postionsbestimmung anhand von Laufzeiten der WLAN-Signale umsetzen lässt. Bedingung hierbei ist, dass der Lokalisierungsdienst - eine reine Softwarelösung darstellt und keine Modifikationen an Hard- oder Firmware voraussetzt und - die Lokalisierung ohne für diese Zwecke ausgelegte Spezialhardware umsetzbar ist. Diese Anforderungen sollen sicherstellen, dass der zu entwickelnde Lokalisierungsdienst mit bereits installierter, handelsübliche Hardware umsetzbar ist. Es sind in Frage kommende Verfahren zur Bestimmung der Signallaufzeit zu erörtern. Für die Laufzeitmessung in Frage kommenden Zeitquellen sollen zugänglich gemacht und auf ihre Tauglichkeit untersucht werden. Durch Messreihen ist zu untersuchen, ob mit den vorgeschlagenen Messverfahren eine Lokalisierung möglich ist und in welchem Rahmen sich die zu erwartende Genauigkeit bewegt. Die in dieser Arbeit beschriebenen Konzepte sollen im Rahmen einer Proof of Concept Anwendung implementiert werden. Die Software soll unter dem Gesichtspunkt der Wiederverwendbarkeit entwickelt werden, um eine spätere Nutzung im Rahmen anderer Projekte zu ermöglichen.

Les transmissions radio à longue portée et basse énergie ouvrent de nouveaux champs d'application pour les capteurs, en particulier pour la surveillance de l'environnement. Le protocole radio LoRa permet, par exemple, de connecter des capteurs à une distance pouvant aller jusqu'à dix kilomètres en ligne de visée. Cependant, la grande surface couverte amène plusieurs difficultés, telles que le placement spatial en regard de la topologie géographique, ou la variabilité de la latence des communications. Le positionnement dans I'environnement comporte également des contraintes liées à I'intérêt des points de mesure du phénomène physique. Les critères de conception de ces réseaux tranchent donc avec les méthodes existantes (disques) quand on s'attaque aux terrains complexes. Cette thèse décrit des techniques de simulation basées sur I'analyse géographique cellulaire pour calculer les couvertures radio à longue portée et déduire les caractéristiques radios dans ces situations. Comme la propagation radio n'est qu'un cas particulier de phénomènes physiques, on montre qu'une approche unifiée cellulaire permet de caractériser beaucoup de comportements physiques potentiels. Le cas des fortes pluies et des inondations est étudié. L'analyse de la géographie est réalisée en utilisant des outils de segmentation pour produire des systèmes cellulaires qui sont à leur tour traduits en code pour des calculs de haute performance. La thèse fournit des résultats d'expériences de terrain complexes pratiques en utilisant LoRa, permettant de qualifier l'exactitude de la simulation des couvertures, et les caractéristiques d'ordonnancement des communications. Nous produisons des tables de performance pour les simulations sur les unités de traitement graphique (GPUs) qui montrent que le choix d'une algorithmique parallèle est pertinent sur ces problèmes. / Long-range radio transmissions open new sensor application fields, in particular for environment monitoring. For example, the LoRa radio protocol enables to connect remote sensors at distance as long as ten kilometers in a line-of-sight. However, the large area covered also brings several difficulties, such as the placement of sensing devices in regard to topology in geography, or the variability of communication latency. Sensing the environment also carries constraints related to the inlerest of sensing points in relation with a physical phenomenon. Thus criteria for designs are evolving a lot from the existing methods, especially in complex terrains. This thesis describes simulation techniques based on geography analysis to compute long-range radio coverages and radio characteristics in these situations. As radio propagation is just a particular case of physical phenomena, it is shown how a unified approach also allows to characterize the behavior of potential physical risks. The case of heavy rainfall and flooding is investigated. Geography analysis is achieved using segmentation tools to produce cellular systems which are in turn translated into code for high-þerformance computations. The thesis provides results from practical complex terrain experiments using LoRa which confirm the accuracy of the simulation, and scheduling characteristics for sample networks. Performance tables are produced for these simulations on current Graphics Processing Units (GPUs).