Papers by OSCAR VINICIO BARRIENTOS VELIZ
Proceedings of the AAAI Conference on Artificial Intelligence
Courses in artificial intelligence and related topics often cover methods for reasoning under unc... more Courses in artificial intelligence and related topics often cover methods for reasoning under uncertainty, decision theory, and game theory. However, these methods can seem very abstract when students first encounter them, and they are often taught using simple “toy” problems. Our goal is to help students to operationalize this knowledge by designing sophisticated autonomous agents that must make complex decisions in games that capture their interest. We describe a tournament-based pedagogy that we have used in two different courses with two different games based on current research topics in artificial intelligence to engage students in designing agents that use strategic reasoning. Many students find this structure very engaging, and we find that students develop a deeper understanding of the abstract strategic reasoning concepts introduced in the courses.
Proceedings of the AAAI Conference on Artificial Intelligence
Game theory is a tool for modeling multi-agent decision problems and has been used to analyze str... more Game theory is a tool for modeling multi-agent decision problems and has been used to analyze strategies in domains such as poker, security, and trading agents. One method for solving very large games is to use abstraction techniques to shrink the game by removing detail, solve the reduced game, and then translate the solution back to the original game. We present a methodology for evaluating the robustness of different game-theoretic solution concepts to the errors introduced by the abstraction process. We present an initial empirical study of the robustness of several solution methods when using abstracted games.
Proceedings of the Annual Hawaii International Conference on System Sciences, 2020
Studies in Computational Intelligence, 2016
Social norms are believed to be the main cause of evolution and establishment of many complex sys... more Social norms are believed to be the main cause of evolution and establishment of many complex systems in human societies, ranging from language lexicon systems to cultural codes of conduct. Revelation of mechanisms behind the emergence of social norms can not only provide us with a better understanding of formation and evolution processes of opinions, conventions and rules in human societies, but more importantly enable us to build and control large-scale complex systems. In this paper, a theoretical framework is proposed to study the emergence of social norms based on agent collective learning and information diffusion in complex relationship networks. In this framework, agents learn collectively from local interactions with their neighbors using multiagent learning methods, and diffuse their learnt information based on their underlying relationships. Extensive experiments are carried out to test the proposed framework in different topological and environmental settings and experimental results show that the framework is effective for emergence of social norms in complex relationship networks. The proposed framework emulates the opinion aggregation and knowledge transfer process in human and the research findings reveal some significant insights into efficient mechanisms of norm emergence in complex relationship networks.
Se realiza el levantamiento Geomagnético en el cerro Merry Hill del Radio Observatorio de Jicamar... more Se realiza el levantamiento Geomagnético en el cerro Merry Hill del Radio Observatorio de Jicamarca el 8 de Setiembre 2010, en cuatro zonas previamente definido. Obteniéndose datos geomagnéticos para 2350 puntos con sus respectivas coordenadas distribuidos regularmente. Para la elaboración del mapa de gradientes geomagnéticos ∆F se ha utilizado dos magnetómetros de protones, un magnetómetro principal “estación móvil” (POS-1 Overhauser) dotado de un GPS para la determinación de las coordenadas y un magnetómetro auxiliar (Scintrex ENVI Mag) como “estación base”. Se ha determinado que las cuatro zonas elegidas muestran un bajo gradiente geomagnético por lo que se ha elegido la zona signado como (zona-02) como la mejor zona que reúne las mejores condiciones para establecer una estación geomagnética para registro continuo y toma de observaciones absolutas. En la zona-02 se ha determinado un punto referencial para observaciones absolutas donde se ha elegido dos puntos referenciales para A...
The Department of Terrestrial Magnetism of the Car negie Institution of Washington founded in 191... more The Department of Terrestrial Magnetism of the Car negie Institution of Washington founded in 1919 the Huancayo Observatory, in Peru (Lat. -12.060, Long - 75.210) and installed a classical magnetometer which has provided a long standing flow of data since March 1st, 1922. Today, there are 10 magnetometers in operation in Peru. On October 13th, 2006, Space Environment Research Center - SERC of Kyushu University installed a new Magnetic Dat a Acquisition System MAGDAS I (PI; Prof. K. Yumoto) at Ancon Observatory (Geographic Latitude: -11.790, Longitude: - 77.160 and Geomagnetic Latitude (2000): 3.100 and Longitude (2000): 354.660). On July 13th, 2011, SERC installed a MAGDAS II at Ica Solar Station (Geographic Latitude: - 140 04' Longitude: -750 44'). Details of the magnetometer that we are hosting will be explained in this presentation.
ABSTRACT New observations of the equatorial thermospheric dynamics observed from Arequipa, Peru (... more ABSTRACT New observations of the equatorial thermospheric dynamics observed from Arequipa, Peru (16.2 S, 72.4 W) obtained with an imaging Fabry-Perot interferometer during the southern hemisphere winter of 2005 (June- August) show an interesting correlation of the formation of the midnight temperature maximum (MTM) with the strength of the semi-diurnal tidal meridional wind. The observations are obtained in eight azimuthal directions at 60 degree zenith angle. Each direction represents an exposure of 120 s and the Doppler shifts and Doppler broadening are analyzed with uncertainties of 8-10 m/s and 30-35 K, respectively. These results are used to prepare horizontal wind maps. When the amplitude of the meridional flow is weak, there is generally not observed any temperature enhancement near midnight. When the meridional flow equatorward is strong, 50-100 m/s, then there is observed about two hours later a significant increase in temperature of typically 100 K. This time delay between the northward component of the thermospheric wind vector and the peak of the MTM structure is observed to be about 30 minutes for two nights obtained during the spring equinox. These results suggest that the semi-diurnal tidal mode forms the MTM by convergence upon the geographical equator to the north of Arequipa. After the compressional heating has taken place, then there is a return "wave" formed that transports the heated air to the region of Arequipa. The decrease of the time delay between winter and the spring equinox is a result of the convergence region forming closer to Arequipa than during the winter. Observations of the horizontal wind maps over successive nights in early July show that the thermospheric wind structure varies considerably from night to night with a variation in the appearance of the meridional wind structure by several hours from night to night. It is tempting to suggest a relationship between this variability and the production of the equatorial spread-F phenomenon.
ABSTRACT Simultaneous Fabry-Perot interferometer (FPI) observations of nighttime thermospheric wi... more ABSTRACT Simultaneous Fabry-Perot interferometer (FPI) observations of nighttime thermospheric winds and temperatures from multiple sites in South America have been obtained from the equinoctial period, September 2010, and from the winter solstice period of June and July 2011. These observations were made at the Peruvian FPI sites at the Jicamarca Radio Observatory (11.96 S, 76.86 W) and Nazca (14.97°S, 74.89°W) and for the Brazilian FPI sites at Cariri (7.38°S, 36.53°W) and Cajazeiras (6.89°S, 38.56°W). A full 12-month climatology record of thermospheric winds and temperatures has been obtained for the two Brazilian FPI sites over the extended solar minimum 2009-2011 period. The analysis of the simultaneous results shows zonal winds that are 50 to 75% faster at Jicamarca, as compared to the zonal wind speeds observed at the two Brazilian sites, with peak winds near 135 to 150 ms-1. This finding is consistent with increased plasma density in the equatorial ionization anomaly over the Brazilian sites, which would produce increased ion drag. For the equinoctial period for both longitudinal sectors, the meridional winds show similar behavior of generally weak winds with northward surges of 50-75 ms-1 occurring at around 22-23 LT and 04-05 LT. This similarity suggests the dominance of the winds by tidal wind forcing from below and is supported by comparison with the WAM meridional wind nighttime behavior. The temperature observations show the appearance of the midnight temperature maximum (MTM) for both longitudinal sectors at almost the same local time (23-24 LT) with similar peak amplitudes of ~100-150 K. The Jicamarca temperatures are seen to be slightly warmer by 25 to 50 K. These results are found to be reasonably consistent with the predictions of the WAM model, which successfully produced a MTM amplitude of much the same magnitude as is observed for all four seaons.
In the low latitude, ionospheric F region, the primary transport mechanism that determines the el... more In the low latitude, ionospheric F region, the primary transport mechanism that determines the electron and ion density distributions is the magnitude of the daytime, upward ExB drift velocity. During the geomagnetic storms on Oct. 29 and 30, 2003, we have inferred these upward ExB drift velocities from ground-based magnetometer observations at Jicamarca and Piura, Peru as a function of
Space Weather, 2004
The daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 10... more The daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100–120 km altitude region within ±2° latitude of the dip equator. A unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the horizontal (H) component between a magnetometer placed directly on the magnetic equator and
Planetary and Space Science, 2008
The hydroxyl nightglow layer is an excellent tracer of the dynamical processes occurring within t... more The hydroxyl nightglow layer is an excellent tracer of the dynamical processes occurring within the mesosphere. A new stereo-imaging method is applied that not only measures the altitude of the airglow layer but also provides a three-dimensional map of the OH-layer centroid heights. A campaign was conducted in July 2006 in Peru to obtain NIR images of the OH nightglow layer which were simultaneously taken for two sites separated by 645 km: Cerro Cosmos (12109 0 08.2 00 S, 75133 0 49.3 00 W, altitude 4630 m) and Cerro Verde Tellolo (16133 0 17.6 00 S, 71139 0 59.4 00 W, altitude 2330 m). Data represented by pairs of images obtained during the nights of July 26-27 and 28-29 are analyzed to yield satellite-type views of the wave field. These are obtained by application of an inversion algorithm. In calculating the normalized cross-correlation parameter for the intensity, three-dimensional maps of the OH nightglow layer surface are retrieved. The mean altitude of the emission profile barycenter is found to be at 87.1 km on July 26 and 89.5 km on July 28. In these two cases the horizontal wavelengths determined are 21.1 and 24.6 km with periods of 18 and 34 min, respectively. A panoramic view of the OH nightglow emission obtained on July 29 at 8 h51-9 h26 UT is presented, in which the overall direction of the waves is found to be N-NW to S-SE, azimuth 1501-3301 (counted from South). The wave kinetic energy density at the OH nightglow layer altitude is 3.9 Â 10 À4 W/kg, which is comparable to the values derived from partial reflection radiowave data.
Journal of Geophysical Research: Space Physics, 2008
Equatorial F region vertical plasma drifts, spread F and anomaly responses, in the south American... more Equatorial F region vertical plasma drifts, spread F and anomaly responses, in the south American longitude sector during the superstorm of 30 October 2003, are analyzed using data from an array of instruments consisting of Digisondes, a VHF radar, GPS TEC and scintillation receivers in Brazil, and a Digisonde and a magnetometer in Jicamarca, Peru. Prompt penetrating eastward electric field of abnormally large intensity drove the F layer plasma up at a velocity $1200 ms À1 during post dusk hours in the eastern sector over Brazil. The equatorial anomaly was intensified and expanded poleward while the development of spread F/plasma bubble irregularities and GPS signal scintillations were weaker than their quiet time intensity. Significantly weaker F region response over Jicamarca presented a striking difference in the intensity of prompt penetration electric field between Peru and eastern longitudes of Brazil. The enhanced post dusk sector vertical drift over Brazil is attributed to electro-dynamics effects arising energetic particle precipitation in the South Atlantic Magnetic Anomaly (SAMA). These extraordinary results and their longitudinal differences are presented and discussed in this paper.
Journal of Atmospheric and Solar-Terrestrial Physics, 2003
... Author Contact Information , E-mail The Corresponding Author , CM Dinardini, JHA Sobral, IS B... more ... Author Contact Information , E-mail The Corresponding Author , CM Dinardini, JHA Sobral, IS Batista, P. Muralikrishna, KN Iyer 1 , O ... used to study the equatorial electrojet irregularities, also at other longitude sectors, notably, in India ( [Reddy 1979]; [Viswanathan 1987]; [Krishna ...
Journal of Atmospheric and Solar-Terrestrial Physics, 2007
The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden to Department of Defense, Washington Headquarters Services Directorate for Information Operations and Reports (0704-0188). 1215 Jefferson Davis Highway, Suite 1204. Arlington VA 22202-4302 Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number
Journal of Atmospheric and Solar-Terrestrial Physics, 2007
Four years of magnetometer data from two locations in Peru, one at the equator and one off the eq... more Four years of magnetometer data from two locations in Peru, one at the equator and one off the equator, have been converted to electric fields and their frequency characteristics (fluctuation spectra) examined. In the frequency range from 0.1 to 30 cycles per hour, the average spectrum monotonically decreases. However, it deviates from a power law in the range 0.3–3 cycles
IEEE Antennas and Propagation Magazine, 2008
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 Inte... more This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Created by The Institute of Electrical and Electronics Engineers (IEEE) for the benefit of humanity.
GPS Solutions, 2003
... Information , E-mail The Corresponding Author , E-mail The Corresponding Author , Bodo Reinis... more ... Information , E-mail The Corresponding Author , E-mail The Corresponding Author , Bodo Reinisch b , Cesar Valladare c , Jorge Chau d and ... via the RayleighTaylor (RT) instability mechanism, which has been well-documented and discussed in Fejer and Kelly (1980) and ...
Geophysical Research Letters, 2002
Annales Geophysicae, 2008
Optical observations of thermospheric winds and temperatures determined with high resolution meas... more Optical observations of thermospheric winds and temperatures determined with high resolution measurements of Doppler shifts and Doppler widths of the OI 630-nm equatorial nightglow emission have been made with improved accuracy at Arequipa, Peru (16.4 • S, 71.4 • W) with an imaging Fabry-Perot interferometer. An observing procedure previously used at Arecibo Observatory was applied to achieve increased spatial and temporal sampling of the thermospheric wind and temperature with the selection of eight azimuthal directions, equally spaced from 0 to 360 • , at a zenith angle of 60 •. By assuming the equivalence of longitude and local time, the data obtained using this technique is analyzed to determine the mean neutral wind speeds and mean horizontal gradients of the wind field in the zonal and meridional directions. The new temperature measurements obtained with the improved instrumental accuracy clearly show the midnight temperature maximum (MTM) peak with amplitudes of 25 to 200 K in all directions observed for most nights. The horizontal wind field maps calculated from the mean winds and gradients show the MTM peak is always preceded by an equatorward wind surge lasting 1-2 h. The results also show for winter events a meridional wind abatement seen after the MTM peak. On one occasion, near the September equinox, a reversal was observed during the poleward transit of the MTM over Arequipa. Analysis inferring vertical winds from the observed convergence yielded inconsistent results, calling into question the validity of this calculation for the MTM structure at equatorial latitudes during solar minimum. Comparison of the observations with the predictions of the NCAR general circulation model indicates that the model fails to reproduce the observed amplitude by a factor of 5 or more. This is attributed in part to the lack of adequate spatial resolution in the model as the MTM phenomenon takes place within a scale of 300-500 km and ∼45 min in local time.
Advances in Space Research, 2010
ABSTRACT A new and original stereo imaging method is introduced to measure the altitude of the OH... more ABSTRACT A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz=83.5–88.0km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3×10−4 and 5.4×10−4J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude.
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Papers by OSCAR VINICIO BARRIENTOS VELIZ