124,735 research outputs found
Receptor super-regenerativo de baixo consumo para redes corporais
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2014.O foco deste trabalho é a análise e o projeto de um receptor super-regenerativo voltado para aplicações biomédicas. Primeiramente, apresenta-se a fundamentação teórica da recepção super-regenerativa e, em seguida, mostra-se um circuito projetado segundo essa arquitetura, a qual incorpora um amplificador de baixo ruído, um oscilador e um detector de envoltória, além de um conversor balanceado-desbalanceado entre estes dois últimos. O projeto demonstra a vantagem dessa técnica para projetar receptores de baixa potência e elevada sensibilidade. Como o oscilador tende a ser o circuito com maior consumo elétrico em um receptor super-regenerativo, esta dissertação também apresenta uma técnica de projeto de osciladores para aplicações de baixa potência. O circuito é baseado no clássico oscilador Colpitts de porta comum com uma segunda fonte de realimentação positiva, a qual é fornecida por uma degeneração indutiva de porta. Esta técnica diminui a transcondutância requerida para originar as oscilações, o que faz com que seja possível reduzir a corrente de polarização e, consequentemente, o consumo de potência. Um protótipo foi produzido em uma tecnologia CMOS padrão de 0,18 µm para servir de prova de conceito. Simulações pós-leiaute demonstraram uma frequência de oscilação de 2,5 GHz com um ruído de fase de -112.9 dBc/Hz a uma frequência deslocada de 1 MHz da portadora, consumindo 124 µW a partir de uma tensão de alimentação de 0,575 V.Abstract : The goal of this work is the analysis and the design of a super-regenerative receiver aimed for biomedical applications. Firstly the theoretical foundation of the super-regenerative reception is presented and afterwards it is shown a circuit designed according such an architecture, which incorporates a lownoise amplifier, an oscillator, and an envelope detector, besides a balancedto- unbalanced converter between the last two. This project demonstrates the advantage of that technique to design low-power and high-sensitivity receivers. Since the oscillator tends to be the circuit with the highest power consumption in a super-regenerative receiver, this dissertation also presents an oscillator design technique for low-power applications. The circuit is based on the common-gate Colpitts oscillator with additional positive feedback provided by an inductive gate degeneration. This technique decreases the required transconductance to start-up oscillations, which makes possible to reduce the bias current and hence the power consumption. A prototype was designed in a standard 0.18 mm CMOS technology as a proof of concept. Post-layout simulations present an oscillating frequency of 2.5 GHz with a phase noise of -112.9 dBc/Hz at a 1 MHz offset frequency and consuming 124 mW from a 0.575-V supply voltage
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
EKF-based dual synchronization of chaotic colpitts circuit and Chua’s circuit
No full textsummary:In this paper, dual synchronization of a hybrid system containing a chaotic Colpitts circuit and a Chua’s circuit, connected by an additive white Gaussian noise (AWGN) channel, is studied via numeric simulations. The extended Kalman filter (EKF) is employed as the response system to achieve the dual synchronization. Two methods are proposed and investigated. The first method treats the combination of a Colpitts circuit and a Chua’s circuit as a higher- dimensional system, while the second method considers the Colpitts circuit and Chua’s circuit separately and utilizes the cross-coupling scheme. The simulation results indicate that the proposed methods can effectively achieve and maintain dual synchronization of the hybrid system through an AWGN channel
A novel hybrid artificial intelligence technique for colpitts oscillator design
No full textIn the design of the common base Colpitts oscillator,
the resistance values of Thevenin’s resistors significantly influenced the transient time and steady state response of the resulting circuit. Various traditional approaches such as intuitive reasoning, mathematical calculation, and simulation-based techniques have been proposed in the literature for this purpose. Some of the aforementioned techniques involve rigorous mathematics, intuition, and experimentation in determining appropriate component values for optimal
performance, stable steady state performance, and short
transient response time from the resulting oscillator. In this paper, a new method of designing Colpitts oscillator using hybrid artificial intelligence comprising evolutionary-based Genetic Algorithm (GA) and artificial neural network (ANN) has been proposed. GA has been used in selecting various optimum resistance values of Thevenin’s resistors for maximizing long-term stability of the outputwaveform thus ensuring stable steady response of the designed circuit. ANN has been utilized in learning the nonlinear relationship between
Thevenin’s resistors and transient time response of the Colpitts oscillator. Upon ANN convergence, optimum resistance values of obtained from GA process are fed into the trained ANN in predicting transient response time of each circuit.
Optimized values with the shortest transient response time are finally selected for the Colpitts oscillator. The designed
circuit successfully achieved optimization between its transient time response and steady state response. Hence, successfully reducing computation associated with existing traditional techniques in designing similar optimum Colpitts oscillator and achieving stable steady state output. Furthermore, this work has also demonstrated that ANN is capable of predicting the transient time of circuit with reasonable
accuracy
Análisis para el diseño de circuitos osciladores de Colpitts con sensores de gas QCM
No full textLas narices electrónicas con base en sensores de microbalanza de cristal de cuarzo (QCM) son ampliamente usadas para la detección y análisis de compuestos orgánicos volátiles. Una película de material químicamente selectiva depositada en los electrodos del QCM lo convierte en un sensor cuya sensibilidad es una función de la frecuencia resonante del cristal piezoeléctrico. Para tal propósito diversos circuitos osciladores se han empleado con el QCM, principalmente usando compuertas lógicas y amplificadores operacionales cuyos límites en las frecuencias de oscilación restringen un aumento de la sensibilidad de la nariz electrónica. En este trabajo se muestra un análisis detallado para el diseño e implementación de una variante del circuito oscilador de Colpitts para QCM empleando un transistor de ultra-alta frecuencia y bajo ruido con la finalidad de usar QCM de frecuencias más altas, realizar pocas modificaciones al circuito paradiferentes QCM e incrementar así la sensibilidad de la nariz electrónica.Palabra(s) Clave(s): nariz electrónica, oscilador colpitts, QCM, sensibilidad
Pragmatic Case Studies as a Source of Unity in Applied Psychology
No full textTo unify or not to unify applied psychology: that is the question. In this article we review pendulum swings in the historical efforts to answer this question—from a comprehensive, positivist, “top-down,” deductive yes between the 1930s and the early 60s, to a postmodern no since then. A rationale and proposal for a limited, “bottom-up,” inductive yes in applied psychology is then presented, employing a case-based paradigm that integrates both positivist and postmodern themes and components. This paradigm is labeled “pragmatic psychology” and, its specific use of case studies, the “Pragmatic Case Study Method” (“PCS Method”). We call for the creation of peer-reviewed journal-databases of pragmatic case studies as a foundational source of unifying applied knowledge in our discipline. As one example, the potential of the PCS Method for unifying different angles of theoretical regard is illustrated in an area of applied psychology, psychotherapy, via the case of Mrs. B. The article then turns to the broader historical and epistemological arguments for the unifying nature of the PCS Method in both applied and basic psychology.Peer reviewe
Dr. Edwin Wright Collection: Author Unknown
No full textNotes - The author relates several short stories about his neighbours including Alex McDonell, homesteading and life around Meanook and Athabasca (1 page
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Osciladores de ultra-baixa-tensão com aplicação em circuitos de captação de energia
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2014Abstract: This thesis describes the analysis and design of oscillators and charge pumps that can operate with very low supply voltages. The focus is on operation of the MOS transistor in the triode region owing to the limited voltage options available. Special attention has been given to the properties of the zero-VT transistor due to its high drive capability at low voltage. In order to investigate the minimum supply voltage for MOSFET oscillators, three topologies were studied. Two of them, namely the enhanced swing ring and the enhanced swing Colpitts oscillators, can operate with supply voltages below the thermal voltage, kT =q. Simplified theoretical expressions for the minimum supply voltage, oscillation frequency and minimum transistor gain of the oscillators were derived. Measurement results obtained using prototypes built with zero-VT transistors verified the operation of the oscillators for a supply voltage as low as 30 mV and 3.5 mV with high swing amplitude for arrangements built with integrated and off-theshelfinductors, respectively. The application of the ultra-low-voltage oscillators to energy harvesting circuits was addressed in this work. In order to convert the ac signal of the oscillator into a dc signal, the popular Dickson charge pump converter was employed. Expressions for the output voltage, input resistance and power converter efficiency of the Dickson charge pump operating at ultra-low voltages were derived. Experimental results obtained with prototypes built with the enhanced swing ring oscillator and the Dickson charge pump confirmed the feasibility of obtaining a dc output equal to 1 V at current consumptions of 100 nA and 1 µA from input voltages of 10 mV and 23 mV, respectively.O presente trabalho apresenta a análise, projeto e experimentação de osciladores e conversores dc-dc elevadores operando a muito baixas tensões de alimentação. Devido aos baixos valores de tensão de alimentação de interesse deste trabalho, especial atenção foi dada à operação do transistor MOS na região triodo e às propriedades do transistor zero-VT, graças a sua alta capacidade de corrente para baixas tensões. Com o objetivo de investigar a mínima tensão de alimentação de osciladores a MOSFET, três topologias foram estudadas. Duas delas, chamadas de oscilador em anel com elevada excursão desinal e oscilador Colpitts com elevada excursão de sinal, podem trabalhar com tensões de alimentação inferiores à tensão térmica, kT /q. Expressões simplificadas para a mínima tensão de alimentação, frequência de oscilação e mínimo ganho do transistor foram derivadas para cada topologia. Resultados experimentais obtidos com protótipos implementados com transistores zero-VT comprovam a operação dos osciladores com tensões tão baixas quanto 30 mV e 3,5 mV em circuitos construídos com indutores integrados e discretos, respectivamente. A aplicação dos osciladores a circuitos de captação de energia (energy harvesting circuits) a partir de fontes de alimentação de ultra-baixa-tensão foi estudada neste trabalho. Com o propósito de converter tensões ac geradas pelos osciladores em sinais dc, o clássico conversor Dickson foi utilizado. Expressões para a tensão de saída, resistência de entrada e eficiência de conversão de potência do conversor Dickson operando a ultra-baixas-tensões foram derivadas. Resultados experimentais obtidos com protótipos construídos com o oscilador em anel com elevada excursão de sinal e com o conversor Dickson, provaram a possibilidade de se obter uma tensão dc na saída de 1 V para correntes de carga de 100 nA e 1 µA a partir de tensões de entrada de 10 mV e 23 mV, respectivamente
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