A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits

We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic non- linear elements. With the discretization of the equations that describe the circuit in the time domain, we obtain a nonlinear algebraic formulation where the unknowns to determine are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits.An efficient scheme to buildtheJacobian matrix with exact partial derivatives with respect to the oscillation period and with re- spect to the samples of the unknowns is described. Without any modifica- tion in the analysis method, the stability of the solution can be computed a posteriori constructing an implicit map, where the last sample is viewed as a function of the previous samples. The application of this technique to the time-delayed Chua's circuit (TDCC) allows us to investigate the stability of the periodic solutions and to locate the period-doubling bifurcations.Peer ReviewedPostprint (published version

Steady state analysis of Chua's circuit with RLCG transmission line

In this paper we present a new technique to compute the steady state response of nonlinear autonomous circuits with RLCG transmission lines. Using multipoint Pade approximants, instead of the commonly used expansions around s=0 or s/spl rarr//spl infin/ accurate, low-order lumped equivalent circuits of the characteristic impedance and the exponential propagation function are obtained in an explicit way. Then, with the temporal discretization of the equations that describe the transformed circuit, we obtain a nonlinear algebraic formulation where the unknowns to be determined are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is obtained. Steady state solutions of the Chua's circuit with RLCG transmission line are computed for selected circuit parameters.Peer ReviewedPostprint (published version

Full machine translation for factoid question answering

In this paper we present an SMT-based approach to Question Answering (QA). QA is the task of extracting exact answers in response to natural language questions. In our approach, the answer is a translation of the question obtained with an SMT system. We use the n-best translations of a given question to find similar sentences in the document collection that contain the real answer. Although it is not the first time that SMT inspires a QA system, it is the first approach that uses a full Machine Translation system for generating answers. Our approach is validated with the datasets of the TREC QA evaluation.Peer ReviewedPreprin

SNR measurement of superregenerative oscillators

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper a method to measure the signal-to-noise ratio of superregenerative oscillators is presented. A spectrum analyzer can easily be coupled to a superregenerative oscillator without paying attention to possible loading effects. With just two measurements of the displayed power spectrum, in combination with the resolution bandwidth of the spectrum analyzer and the quench frequency of the oscillator, the signal-to-noise ratio is determined in a straightforward way. This is supported analytically with results from a frequency-domain analysis technique. Examples of the power displayed by a spectrum analyzer are given to provide insight into the explained procedure.Peer ReviewedPostprint (author's final draft

A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits

We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear elements. With the discretization of the equations that describe the circuit in the time domain, we obtain a nonlinear algebraic formulation where the unknowns to determine are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification in the analysis method, the stability of the solution can be computed a posteriori constructing an implicit map, where the last sample is viewed as a function of the previous samples. The application of this technique to the time-delayed Chua's circuit (TDCC) allows us to investigate the stability of the periodic solutions and to locate the period-doubling bifurcations.Peer ReviewedPostprint (published version

A proof-of-concept superregenerative QPSK transceiver

In this paper we present a description and experimental verification of an HF-band proof-of-concept superregenerative transceiver for QPSK signals. We describe a simple implementation of an all-digital, FPGA-based, QPSK transmitter section. On the receiver side, the quench signal is generated in the same FPGA with a minimum of analog circuitry. As the main novelty, we present a simple synchronization scheme suitable for packetized transmissions.Peer ReviewedPostprint (author’s final draft

An experience of educational technology reported from other times and spaces.

En este artículo narramos nuestra experiencia con alumnas y alumnos de Tecnología Educativa en el curso 2005-2006 de la Facultad de Pedagogía de la Universidad de Barcelona. Se describe el modo en el que confluyen y divergen los tiempos subjetivos, de docentes y estudiantes, los tiempos del grupo clase, los tiempos sociales y de cómo una asignatura como Tecnología educativa nos ayuda a cuestionar, desmontar y proponer alternativas a los tiempos objetivados desde el plan de estudios para permitir la entrada de otros tiempos y espacios.In this article we narrate our experience with students of Educational Technology of the Faculty of Pedagogy of the University of Barcelona in the course 2005-2006. There is described the way in which the subjective times of teachers and students come together and diverge, the times of the group class, the social times and of how a subject as Educational Technology helps us to question, to dismantle and to propose alternatives to the times from the curriculum to allow the entry of other times and spaces

Fatal accident involving a welder employed by a shipping container company, associated with the use of tramadol and antidepressant agents

The widespread use of opioids for the treatment of moderate or severe acute and chronic pain has become a public health problem due to the physical and psychological dependence and tolerance they produce. The increasingly higher doses that patients require may reach toxic levels or lead to accidents, including fatalities. We present the case of a welder who, while working for a shipping container company, fell from height without a safety harness and subsequently died as a result of a traumatic brain injury. Post-mortem examination revealed a cardiac blood tramadol concentration of 2.83 mg/L, which is 3–4 times higher than the maximum therapeutic dose. The combined use of synthetic opioids and antidepressants may heighten the adverse neurological and psychiatric effects. A review of the literature, identified studies, including previous reports of fatalities, supported our causal hypothesis of a serotonin syndrome. This syndrome can lead to a loss of cognitive and sensory capacity, interfere with decision-making ability, and produce mental confusion and dizziness, among other symptoms. In order to prevent harm to themselves and others, all persons who are currently taking these kinds of drugs should avoid dangerous tasks at work and must be advised by a physician regarding the type of activities that are safe for them to perform