Abstract:

We study the double ionization by electron impact of the ground state of heliumlike atoms and propose a scaling law for fully differential (e,3e) cross sections. Within the first Born approximation, cross sections are calculated with a three-body Coulomb (3C) double-continuum wave function and initial states represented by highly accurate wave functions, which satisfy all two-body Kato cusp conditions. We first consider the helium atom in the kinematical and geometrical conditions of the only absolute, high incident energy, experimental data available: our calculations confirm unambiguously that satisfying or not Kato cusp conditions is not a relevant feature of the ground state. Other heliumlike atoms are then considered. Under similar conditions, cross sections for H- are much larger than for helium while the reverse is true for positive ions; a comparison with the rare other theoretical calculations is performed. Finally, within our theoretical framework, we propose an approximate scaling law for (e,3e) cross sections for heliumlike positive ions, and confirm it by calculations. © 2008 The American Physical Society.

Author affiliation: Ancarani, L. U.. Université Paul Verlaine-Metz; Francia

Author affiliation: Dal Cappello, C.. Université Paul Verlaine-Metz; Francia

Author affiliation: Charpentier, I.. Centre National de la Recherche Scientifique; Francia

Author affiliation: Rodriguez, Karina Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Author affiliation: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Abstract:

Author affiliation: Universidad Nacional de Río Negro. Centro de Recursos para el Aprendizaje y la investigación (CRAI); Argentina.

Con el objetivo de brindar a los usuarios de la Biblioteca Electrónica de Ciencia y Tecnología las herramientas necesarias para realizar un eficiente uso de la Biblioteca y, a la vez dar a conocer los alcances del Acceso Abierto a la producción científico-tecnológica y de la Ley No 26.899 Repositorios digitales institucionales de acceso abierto, la Secretaría Ejecutiva de la Biblioteca Electrónica de Ciencia y Tecnología y del Sistema Nacional de Repositorios Digitales, junto al Departamento de Biblioteca Electrónica y Repositorio de la Universidad Nacional de Río Negro organizan en forma conjunta esta actividad de capacitación.

Abstract:

Author affiliation: Universidad Nacional de Río Negro. Centro de Recursos para el Aprendizaje y la investigación (CRAI); Argentina.

Esta actividad profundizará en el uso de todos los recursos disponibles para la Universidad Nacional de Río Negro, así como revistas, libros, estándares, congresos y conferencias, las diferentes estrategias de búsqueda y de organización de este material. En esta instancia también abordarán casos prácticos y aplicables al uso cotidiano, como la utilización de le formulario de préstamo, utilización de buscadores y catálogos, el modo de guardar las búsquedas, la posibilidad de generar una biblioteca personal y otros servicios de valor agregado. Es importante destacar que en el transcurso del año pasado el uso de la Biblioteca Electrónica, por parte de los usuarios de la UNRN, aumentó en un 600%. Este hecho generó, entre otras cosas, el reconocimiento por parte del Ministerio de Educación, Cultura, Ciencia y Tecnología como una institución muy activa en este área, generando acciones en conjunto y defendiendo tanto el acceso como financiamiento de este recurso.

Abstract:

This paper proposes a new algorithm for controlling a formation of multiple autonomous aerial vehicles based on multiple control objectives. The strategy includes using the null space of a Jacobian matrix to achieve the different control objectives in a non-conflicting way. The mission is split into two elementary tasks, with suitable command references generated for each robot. The commands for each task are combined through a hierarchical method by using the projection of commands onto the null space. The incorporation of ground vehicles in the control scheme is also considered, thus extending the proposed scheme for controlling heterogeneous formations. The stability analysis of the control system shows that such a system is asymptotically stable, and experimental results validate the proposed control system.

Author affiliation: Rosales, Claudio Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina

Author affiliation: Leica Arteaga, Paulo Cesar. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina

Author affiliation: Sarcinelli Filho, Mario. Universidade Federal do Espírito Santo; Brasil

Author affiliation: Scaglia, Gustavo Juan Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina

Author affiliation: Carelli Albarracin, Ricardo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina

Abstract:

A 2-GS/s 6-bit time interleaved (TI) successive approximation register (SAR) analog-to-digital converter (ADC) is designed and fabricated in a 0.13 lm CMOS process. The architecture uses 8 time-interleaved track-andhold amplifiers (THA) and 16 asynchronous SAR ADCs. The sampling frequency of the TI-ADC can be set from 200 MHz to more than 2 GHz. The chip includes a programmable delay cell array to adjust up to 25 % the sampling clock phase in each THA, and a multi-channel low voltage differential signaling interface capable of transmitting at full sampling rate (>12 Gb/s), without decimation, off-chip. These blocks make the fabricated ADC an excellent platform to test/evaluate mixed-signal calibration algorithms, which are of great interest for application in high-speed optical systems. Measurements of the fabricated ADC show a peak signal-to-noise-and-distortion ratio of 33.9 dB and a power consumption of 192 mW at 1.2 V.

Author affiliation: Reyes, Benjamín Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; Argentina

Author affiliation: Paulina, Gustavo German. Fundación Fulgor; Argentina

Author affiliation: Sanchez, Raul. Fundación Fulgor; Argentina

Author affiliation: Mandolesi, Pablo Sergio. Universidad Nacional del Sur; Argentina

Author affiliation: Hueda, Mario Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; Argentina

Abstract:

A novel Bayesian technique for the joint estimation of real and integer parameters in a linear measurement model is presented. The integer parameters take values on a finite set, and the real ones are assumed to be a Gaussian random vector. The posterior distribution of these parameters is sequentially determined as new measurements are incorporated. This is a mixed distribution with a Gaussian continuous part and a discrete one. Estimators for the integer and real parameters are derived from this posterior distribution. A Maximum A Posteriori (MAP) estimator modified with the addition of a confidence threshold is used for the integer part and a Minimum Mean Squared Error (MMSE) is used for the real parameters. Two different cases are addressed: i) both real and integer parameters are time invariant and ii) the integer parameters are time invariant but the real ones are time varying. Our technique is applied to the GNSS carrier phase ambiguity resolution problem, that is key for high precision positioning applications. The good performance of the proposed technique is illustrated through simulations in different scenarios where different kind of measurements as well as different satellite visibility conditions are considered. Comparisons with state-of-the-art ambiguity solving algorithms confirm performance improvement. The new method is shown to be useful not only in the estimation stage but also for validating the estimates ensuring a predefined success rate through proper threshold selection.

Abstract:

Educational robotics proposes the use of robots as a teaching resource that enables inexperienced students to approach topics in fields unrelated to robotics. In recent years, these activities have grown substantially in elementary and secondary school classrooms and also in outreach experiences to interest students in science, technology, engineering, and math (STEM) undergraduate programs. A key problem in educational robotics is providing a satisfactory, adequate, easy-to-use interface between an inexpert public and the robots. This paper presents a behavior-based application for programming robots and the design of robotic-centered courses and other outreach activities. Evaluation data show that over 90% of students find it easy to use. These activities are part of a comprehensive outreach program conducted by the Exact and Natural Science Faculty of the University of Buenos Aires, Argentina (FCEN-UBA). Statistical data show that since 2009 over 35% of new students at the FCEN-UBA have participated in some outreach activity, suggesting their significant impact on student enrollment in STEM-related programs.

Author affiliation: de Cristóforis, Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Pedre, Sol. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Nitsche, Matias Alejandro. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Fischer, Thomas. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Pessacg, Facundo Hugo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Di Pietro, Carlos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina

Abstract:

Most of the existing characterizations of the integral input-to-state stability (iISS) property are not valid for time-varying or switched systems in cases where converse Lyapunov theorems for stability are not available. This paper provides a characterization that is valid for switched and time-varying systems, and shows that natural extensions of some of the existing characterizations result in only sufficient but not necessary conditions. The results provided also pinpoint suitable iISS gains and relate these to supply functions and bounds on the function defining the system dynamics.

Author affiliation: Haimovich, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas. Universidad Nacional de Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas; Argentina

Author affiliation: Mancilla Aguilar, Jose Luis. Instituto Tecnológico de Buenos Aires; Argentina

Abstract:

In this letter, we use the Berry-Esseen theorem and the method of tilted distributions to derive a simple tight closed-form approximation for the tail probabilities of a sum of independent but not necessarily identically distributed random variables. We also provide lower and upper bounds. The expression can also be used for computing the cumulative distribution function. We illustrate the accuracy of the method by analyzing some convergence properties of the theoretical approximation and comparing it with previous results in the literature when available and/or numerical results.

Author affiliation: Maya, Juan Augusto. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Rey Vega, Leonardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; Argentina

Author affiliation: Galarza, Cecilia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; Argentina

Abstract:

Due to the technological breakthrough of recent years, electronic devices have become an important part of everyday life. Most of these devices falls within the class of systems called embedded systems. This article presents a proposal for a course on embedded systems. The proposal is based on a<br />constructivist approach to teaching, with particular emphasis on problem-based learning.

Author affiliation: Ordinez, Leonardo Damian. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Bahia Blanca. Instituto de Invest.en Ing.Electrica; Argentina

Author affiliation: Alimenti, Omar Ruben. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Bahia Blanca. Instituto de Invest.en Ing.Electrica; Argentina