Systematic methodology for the global stability analysis of nonlinear circuits

A new methodology for the detection of Hopf, flip, and turning-point bifurcations in nonlinear circuits analyzed with harmonic balance (HB) is presented. It enables a systematic determination of bifurcation loci in terms of relevant parameters, such as input power, input frequency, and bias voltages, for instance. It does not rely on the use of continuation techniques and is able to globally provide the entire loci, often containing multivalued sections and/or disconnected curves, in a single simulation. The calculation of Hopf and flip bifurcations is based on the extraction of a small-signal admittance/impedance function from HB and the calculation of its zeros through a geometrical procedure. The method is ideally suited for the investigation of the global stability properties of power amplifiers and other nonlinear circuits. The turning-point locus, associated with either jump phenomena or synchronization, is obtained by taking into account the annihilation/generation of steady-state solutions that is inherent to this type of bifurcation. A technique is also presented for the exhaustive calculation of oscillation modes in multidevice oscillators and oscillators loaded with multiresonance networks. The new methodologies are illustrated through their application to a power amplifier and a multimode oscillator.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under research projects TEC2014-60283-C3-1-R and TEC2017-88242-C3-1-R

Envelope-domain analysis and modeling of super-regenerative oscillators

An envelope-domain methodology for the numerical modeling of super-regenerative oscillators (SROs) is presented. The main advantage is its generality of application to transistor-based oscillators with arbitrary topology. Initially, a stability analysis of the nonoscillatory steady-state solution, forced by the quench signal, is performed. It is based on the calculation of a linear-time-variant (LTV) transfer function, obtained by linearizing the circuit envelope-domain equations about the nonoscillatory regime. Under moderate quench frequencies, it will be possible to estimate the SRO normalized envelope and sensitivity function from the detected dominant pair of complex-conjugate poles. In the general case, the SRO oscillatory response is modeled with a numerical method, valid under linear operation with respect to the input signal. This is based on the calculation of the LTV impulse response from a time-frequency transfer function obtained under a small-signal sinusoidal excitation. The LTV impulse response enables a straightforward determination of the sensitivity time interval and time distance to the envelope maximum. An integral expression, in terms of the LTV transfer function, will provide the SRO response to any small-signal input with any arbitrarily carrier frequency and modulation. The methodology has been successfully validated through its application to an SRO at 2.7 GHz, which has been manufactured and measured.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under Research Project TEC2014-60283-C3-1-R and Research Project TEC2017-88242-C3-1-

Analysis of superregenerative oscillators in nonlinear mode

Superregenerative oscillators in a nonlinear mode are investigated in detail using methodologies based on envelope transient, complemented with additional algorithms. A maximum-detection technique is applied to obtain the input-power threshold for nonlinear operation under different implementations of the quench signal. A mapping procedure enables the prediction of hangover and self-oscillation effects. It is based on the detection of the sequence of local maxima in the envelope amplitude after the application of a single input pulse. Using a contour-intersection method, and depending on the analysis time interval, it is possible to quantify the hangover effects and obtain the oscillation boundary, in terms of any two significant parameters. Then, a compact time-variant behavioral model is derived, valid in the absence of hangover and self-oscillation effects. It consists of a single time-variant Volterra kernel and is applicable provided that the amplitude transitions occur outside the sensitivity interval. Various methodologies are tested in a practical FET-based oscillator at 2.7 GHz. The prototype has been manufactured and measured, obtaining good agreement with the analysis results.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R

Resistencia a la proteína C activada en los accidentes cerebrovasculares

Tesis de la Universidad Complutense de Madrid, Facultad de Medicina, Departamento de Medicina, leída el 17-01-1997Introducción: la resistencia a la proteína c activada (rpca), es un defecto de carácter congénito que se ha revelado como la mayor causa de trombofilia idiopatica. El defecto consiste en una falta de respuesta a la proteína c activada (pca), potente anticoagulante natural, y se detecta mediante un sencillo test de ttpa (tiempo de cefalina). Objetivos: estandarizar el método de medida de la rpca y determinar su incidencia, en comparación con otras alteraciones hemostáticas, en los pacientes con acv. Material y método: se estudian un total de 433 controles para determinar las diferencias en la rpca según sexo, edad y congelación de las muestras, y para calcular el rango de referencia. Por otro lado, un grupo de 160 pacientes con acv en los que se determinan la rpca y otros parámetros hemostáticos. Rpca se mide por método coagulometrico (test ttpa). Resultados y conclusiones: nuestros resultados coinciden con los de otros autores, perfilándose la rpca como el factor de riesgo para acv mas potente de los estudiados. En la población general, la prevalencia de rpca es similar independientemente de sexo y edad. En cambio, la congelación de las muestras si muestra diferencias, siendo mayores los valores de rpca cuando se determinan en plasma fresco. En cualquier caso, siempre es fundamental estandarizar el método de medida, debiéndose determinar de antemano reactivos y rango de referencia a utilizar por cada laboratorio.Fac. de MedicinaTRUEpu

Proposal of didactic-technological resources to attend the Gifted Students

En el presente artículo se realiza una introducción que guía al lector sobre la actualidad normativa de la atención educativa al alumnado con Altas Capacidades. Posteriormente, se define el concepto de Tecnologías de la Información y la Comunicación (TIC, en adelante), así como se resaltan algunos de sus beneficios, para terminar realizando una propuesta de recursos didáctico-tecnológicos que potencien el desarrollo de los talentos de los estudiantes con Altas Capacidades. Todo ello a través de una perspectiva inclusiva de la tecnología.In the present article is made an introduction that guides the reader on the normative actuality of the educational attention to the Gifted Students. Subsequently, the concept of Information and Communication Technologies (ICT, hereafter) is defined, as well as highlighting some of its benefits, to finish making a proposal of didactic-technological resources that promote the development of the talents of the Gifted Students. All this through an inclusive perspective of technology

Efectos de la Guerra de Independencia española en la política estadounidense

[ES] Se aborda en este artículo la repercusión del conflicto hispano-francés al otro lado del Atlántico y, en particular, en Estados Unidos teniendo además en cuenta el papel que desempeñan Francia e Inglaterra en el establecimiento de las relaciones intercontinentales. Asimismo se analizan las ventajas territoriales, estratégicas y comerciales obtenidas por Estados Unidos.[EN] This study deals with the repercussions of the Spanish-French conflict on the other side of the Atlantic, and in particular, the United States, taking into account the role of France and England in the establishment of intercontinental relations. The territorial, strategic and commercial advantages obtained by the US are also analysed

Bastidores diplomáticos y fuerzas políticas: Santo Domingo en la política internacional (siglo XIX)

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Effects of the Spanish War of Independence on United States Policy

This study deals with the repercussions of the Spanish-French conflict on the other side of the Atlantic, and in particular, the United States, taking into account the role of France and England in the establishment of intercontinental relations. The territorial, strategic and commercial advantages obtained by the US are also analysed