Experimental study of artificial neural networks using a digital memristor simulator

© 2018 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.This paper presents a fully digital implementation of a memristor hardware simulator, as the core of an emulator, based on a behavioral model of voltage-controlled threshold-type bipolar memristors. Compared to other analog solutions, the proposed digital design is compact, easily reconfigurable, demonstrates very good matching with the mathematical model on which it is based, and complies with all the required features for memristor emulators. We validated its functionality using Altera Quartus II and ModelSim tools targeting low-cost yet powerful field programmable gate array (FPGA) families. We tested its suitability for complex memristive circuits as well as its synapse functioning in artificial neural networks (ANNs), implementing examples of associative memory and unsupervised learning of spatio-temporal correlations in parallel input streams using a simplified STDP. We provide the full circuit schematics of all our digital circuit designs and comment on the required hardware resources and their scaling trends, thus presenting a design framework for applications based on our hardware simulator.Peer ReviewedPostprint (author's final draft

Optimal CCD readout by digital correlated double sampling

Digital correlated double sampling (DCDS), a readout technique for charge-coupled devices (CCD), is gaining popularity in astronomical applications. By using an oversampling ADC and a digital filter, a DCDS system can achieve a better performance than traditional analogue readout techniques at the expense of a more complex system analysis. Several attempts to analyse and optimize a DCDS system have been reported, but most of the work presented in the literature has been experimental. Some approximate analytical tools have been presented for independent parameters of the system, but the overall performance and trade-offs have not been yet modelled. Furthermore, there is disagreement among experimental results that cannot be explained by the analytical tools available. In this work, a theoretical analysis of a generic DCDS readout system is presented, including key aspects such as the signal conditioning stage, the ADC resolution, the sampling frequency and the digital filter implementation. By using a time-domain noise model, the effect of the digital filter is properly modelled as a discrete-time process, thus avoiding the imprecision of continuous-time approximations that have been used so far. As a result, an accurate, closed-form expression for the signal-to-noise ratio at the output of the readout system is reached. This expression can be easily optimized in order to meet a set of specifications for a given CCD, thus providing a systematic design methodology for an optimal readout system. Simulated results are presented to validate the theory, obtained with both time- and frequency-domain noise generation models for completeness.Comment: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record is available online via the DOI or at: http://mnras.oxfordjournals.org/content/455/2/1443.full.pd

El paradigma de la sociedad de sospecha en Chile: análisis crítico de una política criminal basada en el estado de policía

Treballs Finals del Màster de Criminologia, Política Criminal i Sociologia Juridicopenal, Facultat de Dret, Universitat de Barcelona, Curs: 2014-2015, Tutors: Antonio Madrid Pérez i Alejandro GoldbergEn este trabajo examinamos y analizamos la existencia de un estatus jurídico de sospechoso, a partir del cual se propone una política criminal basada en la selectividad y exclusión de ciertos sectores e individuos de la sociedad. Dicha política criminal se implementa en el contexto de un permanente discurso securitario que propone la producción de un Derecho penal de características autoritarias, muchas veces basada en el derecho penal de autor (y no del hecho), que crea categorías de delitos que se estructuran a partir de una presunción de culpa, y que la doctrina denomina “delitos de sospecha”, normas que son abiertamente inconstitucionales por poner en juego derechos fundamentales, como la presunción de inocencia. El foco de atención de nuestro análisis está puesto en el caso chileno. Este discurso, y esta política –en definitiva– permea hacia los juzgados y las policías quienes llevan a cabo acciones que, a través de interpretaciones extensivas de ciertas instituciones del Derecho penal, reviven prácticas que se creían superadas, como lo es la detención por sospecha. En este contexto se funda –a nuestro juicio– el paradigma de la sociedad de sospecha, el cual estigmatiza a comunidades y grupos de la sociedad, en constante lucha por recuperar sus derechos, que terminan sucumbiendo frente a una sociedad que sospecha de ellos permanentemente

Resistive switching behavior seen from the energy point of view

The technology of Resistive Switching (RS) devices (memristors) is continuously maturing on its way towards viable commercial establishment. So far, the change of resistance has been identified as a function of the applied pulse characteristics, such as amplitude and duration. However, parameter variability holds back any universal approach based on these two magnitudes, making also difficult even the qualitative comparison between different RS material compounds. On the contrary, there is a relevant magnitude which is much less affected by device variability; the energy. In this direction, we doubt anyone so far has ever wondered 'what is the quantitative effect of the injected energy on the device state?' Interestingly, a first step was made recently towards the definition of performance parameters for this emerging device technology, using as fundamental parameter the energy. In this work, we further elaborate on such ideas, proving experimentally that the 'resistance change per energy unit' (dR/dE) can be considered a significant magnitude in analog operation of bipolar memristors, being a key performance parameter worth of timely disclosure.Peer ReviewedPostprint (author's final draft

Desempeño que requiere la formación inicial docente en el ámbito de la investigación

Tesis (Profesor de Educación Física para la Enseñanza Básica, Licenciado en Educación)En la presente investigación, han sido recopilados, revisados, expuestos y analizados una serie de documentos de diversos orígenes y fuentes, de origen nacional e internacional, de autorías individuales y grupales, relacionados con el ámbito de la investigación y la importancia que se otorga a esta en el mundo de la educación en general y el ámbito formativo de docentes. Dichos documentos serán utilizados como marco teórico, con el fin de establecer las falencias y fortalezas existentes en el actual proceso de formación docente y en el proceso de Seminario de Grado de 4º año de la carrera de Educación Física de la Universidad Andrés Bello (UNAB) en lo que respecta a la investigación e indagación científica, además de establecer los diversos desempeños que requiere la formación inicial docente (FID) en el ámbito investigativo. Por otro lado, en base a los documentos revisados durante la investigación y las conclusiones obtenidas al respecto, se espera establecer un diagnóstico que pueda ser de utilidad para la Universidad Andrés Bello a la hora de plantearse cambios en innovaciones en la malla curricular de la carrera de Educación Física que en ella se imparte

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022

Measurement of shower development and its Moli\`ere radius with a four-plane LumiCal test set-up

A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Moli\`ere radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Table

ECFA Detector R&D Panel, Review Report

Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha scattering events with a precision better than 10$^{-3}$ at the ILC and 10$^{-2}$ at CLIC, and a low polar-angle calorimeter (BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam interactions and physics background processes on the luminosity measurement, and of beamstrahlung on the performance of BeamCal, as well as to optimise the design of both calorimeters. Dedicated sensors, front-end and ADC ASICs have been designed for the ILC and prototypes are available. Prototypes of sensor planes fully assembled with readout electronics have been studied in electron beams.Comment: 61 pages, 51 figure