A linear programming methodology for approximate dynamic programming

[EN] The linear programming (LP) approach to solve the Bellman equation in dynamic programming is a well-known option for finite state and input spaces to obtain an exact solution. However, with function approximation or continuous state spaces, refinements are necessary. This paper presents a methodology to make approximate dynamic programming via LP work in practical control applications with continuous state and input spaces. There are some guidelines on data and regressor choices needed to obtain meaningful and well-conditioned value function estimates. The work discusses the introduction of terminal ingredients and computation of lower and upper bounds of the value function. An experimental inverted-pendulum application will be used to illustrate the proposal and carry out a suitable comparative analysis with alternative options in the literature.The authors are grateful for the financial support of the Spanish Ministry of Economy and the European Union, grant DPI2016-81002-R (AEI/FEDER, UE), and the PhD grant from the Government of Ecuador (SENESCYT).Diaz, H.; Sala, A.; Armesto Ángel, L. (2020). A linear programming methodology for approximate dynamic programming. International Journal of Applied Mathematics and Computer Science (Online). 30(2):363-375. https://doi.org/10.34768/amcs-2020-0028S36337530

Fitted Q-Function Control Methodology Based on Takagi-Sugeno Systems

"© 2020 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng 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."[EN] This paper presents a combined identification/ Q-function fitting methodology that involves identification of a Takagi-Sugeno model, computation of (sub)optimal controllers from linear matrix inequalities (LMIs), and subsequent data-based fitting of the Q-function via monotonic optimization. The LMI-based initialization provides a conservative solution, but it is a sensible starting point to avoid convergence/local-minima issues in raw data-based fitted Q-iteration or Bellman residual minimization. An inverted-pendulum experimental case study illustrates the approach.This work was supported in part by the Spanish Ministry of Economy and European Union (AEI/FEDER, UE) under Grant DPI2016-81002-R and in part by the Government of Ecuador through the Ph.D. Grant SENESCYT.Diaz-Iza, HP.; Armesto, L.; Sala, A. (2020). Fitted Q-Function Control Methodology Based on Takagi-Sugeno Systems. IEEE Transactions on Control Systems Technology. 28(2):477-488. https://doi.org/10.1109/TCST.2018.2885689S47748828

M31N 2008-05d: A M 31 disk nova with a dipping supersoft X-ray light curve

Classical novae (CNe) represent a major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. Significantly different SSS properties of CNe in the M 31 bulge and disk were indicated by recent X-ray population studies, which however considered only a small number of disk novae. We initiated a target of opportunity (ToO) program with XMM-Newton to observe the SSS phases of CNe in the disk of M 31 and improve the database for further population studies. We analysed two XMM-Newton ToO observations triggered in Aug 2011 and Jan 2012, respectively, and extracted X-ray spectra and light curves. We report the discovery of an X-ray counterpart to the M 31 disk nova M31N 2008-05d. The X-ray spectrum of the object allows us to classify it as a SSS parametrised by a blackbody temperature of 32+/-6 eV. More than three years after the nova outburst, the X-ray light curve of the SSS exhibits irregular, broad dip features. These dips affect primarily the very soft part of the X-ray spectrum, which might indicate absorption effects. Dipping SSS light curves are rarely observed in M 31 novae. As well as providing an unparalleled statistical sample, the M 31 population of novae with SSS counterparts produces frequent discoveries of unusual objects, thereby underlining the importance of regular monitoring.Comment: 6 pages, 4 figures, 1 table; accepted by Astronomy and Astrophysic

Nova M31N 2007-12b: Supersoft X-rays reveal an intermediate polar?

For the He/N nova M31N 2007-12b, we analyzed XMM-Newton EPIC and Chandra HRC-I observations of our monitoring program performed at intervals of ten days and added results of a XMM-Newton target of opportunity observation and Swift XRT observations. The supersoft source (SSS) emission started between 21 and 30 d after the optical outburst and ended between 60 and 120 d after outburst, making M31N 2007-12b one of the few novae with the shortest SSS phase known. The X-ray spectrum was supersoft and can be fitted with a white dwarf (WD) atmosphere model with solar abundances absorbed by the Galactic foreground. The temperature of the WD atmosphere seems to increase at the beginning of the SSS phase from ~70 to ~80 eV. The luminosity of M31N 2007-12b during maximum was at the Eddington limit of a massive WD and dropped by ~30% in the observation 60 d after outburst. The radius of the emission region is ~6x10^8 cm. In the four bright state observations, we detected a stable 1110 s pulsation, which we interpret as the WD rotation period. In addition, we detect dips in three observations that might represent a 4.9 h or 9.8 h binary period of the system. Nova envelope models with <50% mixing between solar-like accreted material and the degenerate core of the WD can be used to describe the data. We derive a WD mass of 1.2 Msun, as well as an ejected and burned mass of 2.0x10^{-6} Msun} and 0.2x10^{-6} Msun, respectively. The observed periodicities indicate that nova M31N 2007-12b erupted in an intermediate polar (IP) system. The WD photospheric radius seems to be larger than expected for a non-magnetic WD but in the range for magnetic WDs in an IP system. (abridged)Comment: 10 pages, 5 figures, A&A accepte

From X-ray dips to eclipse: Witnessing disk reformation in the recurrent nova USco

The 10th recorded outburst of the recurrent eclipsing nova USco was observed simultaneously in X-ray, UV, and optical by XMM-Newton on days 22.9 and 34.9 after outburst. Two full passages of the companion in front of the nova ejecta were observed, witnessing the reformation of the accretion disk. On day 22.9, we observed smooth eclipses in UV and optical but deep dips in the X-ray light curve which disappeared by day 34.9, then yielding clean eclipses in all bands. X-ray dips can be caused by clumpy absorbing material that intersects the line of sight while moving along highly elliptical trajectories. Cold material from the companion could explain the absence of dips in UV and optical light. The disappearance of X-ray dips before day 34.9 implies significant progress in the formation of the disk. The X-ray spectra contain photospheric continuum emission plus strong emission lines, but no clear absorption lines. Both continuum and emission lines in the X-ray spectra indicate a temperature increase from day 22.9 to day 34.9. We find clear evidence in the spectra and light curves for Thompson scattering of the photospheric emission from the white dwarf. Photospheric absorption lines can be smeared out during scattering in a plasma of fast electrons. We also find spectral signatures of resonant line scattering that lead to the observation of the strong emission lines. Their dominance could be a general phenomenon in high-inclination systems such as Cal87.Comment: Submitted to ApJ. 16 pages, 16 figure

Shortcut to adiabaticity in spinor condensates

We devise a method to shortcut the adiabatic evolution of a spin-1 Bose gas with an external magnetic field as the control parameter. An initial many-body state with almost all bosons populating the Zeeman sublevel m = 0 is evolved to a final state very close to a macroscopic spin-singlet condensate, a fragmented state with three macroscopically occupied Zeeman states. The shortcut protocol, obtained by an approximate mapping to a harmonic oscillator Hamiltonian, is compared to linear and exponential variations of the control parameter. We find a dramatic speedup of the dynamics when using the shortcut protocol

Fear of falling in women with fibromyalgia and its relation with number of falls and balance performance

Objetivo. Para evaluar el miedo de caer, el número de caídas, y equilibrar el rendimiento en mujeres con FM y para examinar la relación entre estas variables y otras, como el equilibrio entre rendimiento, calidad de vida, la edad, el dolor y el impacto de la fibromialgia. Los métodos. Un total de 240 mujeres participaron en este estudio transversal. De ellos, 125 tenían la fibromialgia. Se evaluaron diferentes variables: edad, miedo de caer desde 0 a 100, el número de caídas, composición corporal, el equilibrio entre rendimiento, resistencia en las extremidades inferiores, la calidad de vida relacionada con la salud, y el impacto de la fibromialgia. Los resultados. Las mujeres con fibromialgia informaron de más caídas y más miedo de caer. Miedo de caer estaba asociada con el número de caídas en el último año, la rigidez, la percepción de los problemas de equilibrio, el impacto y la HRQoL de FM, mientras que el número de caídas se relaciona con el miedo de caer, equilibrar el rendimiento con los ojos cerrados, dolor, sensibilidad al tacto, ansiedad, auto-reportado problemas de equilibrio, impacto de FM, y la HRQoL. Conclusión. FM tiene un impacto sobre el miedo de caer, equilibrar el rendimiento, y el número de caídas. Equilibrio percibido problemas parecen estar más estrechamente asociadas con el miedo de caer de equilibrio objetivo de rendimiento.Objective. To evaluate fear of falling, number of falls, and balance performance in women with FMand to examine the relationship between these variables and others, such as balance performance, quality of life, age, pain, and impact of fibromyalgia. Methods. A total of 240 women participated in this cross-sectional study. Of these, 125 had fibromyalgia. Several variables were assessed: age, fear of falling from 0 to 100, number of falls, body composition, balance performance, lower limb strength, health-related quality of life, and impact of fibromyalgia. Results. Women with fibromyalgia reported more falls and more fear of falling. Fear of falling was associated with number of falls in the last year, stiffness, perceived balance problems, impact of FM, and HRQoL whereas the number of falls was related to fear of falling, balance performance with eyes closed, pain, tenderness to touch level, anxiety, self-reported balance problems, impact of FM, and HRQoL. Conclusion. FM has an impact on fear of falling, balance performance, and number of falls. Perceived balance problems seem to be more closely associated with fear of falling than objective balance performance.Trabajo patrocinado por: Ministerio de Economía, Industria y Competitividad. DEP2012-39828 (I+D+i) Ministerio de Educación, Cultura y Deporte. FPU14/01283, para Daniel Collado Mateo Gobierno de Extremadura y Fondos de Desarrollo Regional (FEDER). GR10127 Fundación Tatiana Pérez de Guzmán el Bueno. Beca predoctoral para Daniel Collado MateopeerReviewe

Prediction of the yield of grains through artificial intelligence

Grass turns out to be an appropriate food for cattle, mainly in tropical climate countries such as Latin American countries. This is due to the high number of species that can be used, the possibility of growing them year-round, the ability of the ruminant to use fibrous supplies and be an economic source (Sánchez et al., Data mining and big data. DMBD 2018. Lecture notes in computer science, vol 10943. Springer, Cham, 2018, [1]). In this work, an application of neural networks was carried out in the forecasting of more accurate values of production and quality of grasslands

Prevalence of Peripheral Arterial Disease and Associated Vascular Risk Factors in 65-Years-Old People of Northern Barcelona

Asintomático; Factores de riesgo cardiovascular; PrevalenciaAsimptomàtic; Factors de risc cardiovascular; PrevalençaAsymptomatic; Cardiovascular risk factors; PrevalenceObjective: To determine the prevalence and risk factors associated with peripheral arterial disease (PAD) in Northern Barcelona at 65 years of age. Methods: A single-center, cross-sectional study, including males and females 65 years of age, health care cardholders of Barcelona Nord. PAD was defined as an ankle–brachial index (ABI) < 0.9. Attending subjects were evaluated for a history of common cardiovascular risk factors. A REGICOR score was obtained, as well as a physical examination and anthropometric measurements. Results: From November 2017 to December 2018, 1174 subjects were included: 479 (40.8%) female and 695 (59.2%) male. Overall prevalence of PAD was 6.2% (95% CI: 4.8–7.6%), being 7.9% (95% CI: 5.9–9.9%) in males and 3.8% (95% CI: 2.1–5.5%) in females. An independent strong association was seen in male smokers and diabetes, with ORs pf 7.2 (95% CI: 2.8–18.6) and 1.8 (95% CI: 1.0–3.3), respectively, and in female smokers and hypertension, with ORs of 5.2 (95% CI: 1.6–17.3) and 3.3 (95% CI: 1.2–9.0). Male subjects presented with higher REGICOR scores (p < 0.001). Conclusion: Higher-risk groups are seen in male subjects with a history of smoking and diabetes and female smokers and arterial hypertension, becoming important subgroups for our primary healthcare centers and should be considered for ABI screening programs.This work was logistically supported by the PERIS 2016–2020 medical research grant from Generalitat de Catalunya (Spain). Expedient Number SLT002/16/00441