Planning with Information-Processing Constraints and Model Uncertainty in Markov Decision Processes

Information-theoretic principles for learning and acting have been proposed to solve particular classes of Markov Decision Problems. Mathematically, such approaches are governed by a variational free energy principle and allow solving MDP planning problems with information-processing constraints expressed in terms of a Kullback-Leibler divergence with respect to a reference distribution. Here we consider a generalization of such MDP planners by taking model uncertainty into account. As model uncertainty can also be formalized as an information-processing constraint, we can derive a unified solution from a single generalized variational principle. We provide a generalized value iteration scheme together with a convergence proof. As limit cases, this generalized scheme includes standard value iteration with a known model, Bayesian MDP planning, and robust planning. We demonstrate the benefits of this approach in a grid world simulation.Comment: 16 pages, 3 figure

Is normalization necessary for stable model reference adaptive control?

Published versio

PPAK Wide-field Integral Field Spectroscopy of NGC 628: I. The largest spectroscopic mosaic on a single galaxy

We present a wide-field IFS survey on the nearby face-on Sbc galaxy NGC 628, comprising 11094 individual spectra, covering a nearly circular field-of-view of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the optical wavelength range (3700--7000 AA). This galaxy is part of the PPAK IFS Nearby Galaxies Survey, (PINGS, Rosales-Ortega et al. 2009). To our knowledge, this is the widest spectroscopic survey ever made in a single nearby galaxy. A detailed flux calibration was applied, granting a spectrophotometric accuracy of $\sim$\,0.2 mag. The age of the stellar populations shows a negative gradient from the inner (older) to the outer (younger) regions. We found an inversion of this gradient in the central ~1 kpc region, where a somewhat younger stellar population is present within a ring at this radius. This structure is associated with a circumnuclear star-forming region at ~ 500 pc, also found in similar spiral galaxies. From the study of the integrated and spatially resolved ionized gas we found a moderate SFR of ~ 2.4 Msun yr$^{-1}$. The oxygen abundance shows a a clear gradient of higher metallicity values from the inner part to the outer part of the galaxy, with a mean value of 12~+~log(O/H) ~ 8.7. At some specific regions of the galaxy, the spatially resolved distribution of the physical properties show some level of structure, suggesting real point-to-point variations within an individual \hh region. Our results are consistent with an inside-out growth scheme, with stronger star formation at the outer regions, and with evolved stellar populations in the inner ones.Comment: 31 pages, 22 Figuras, Accepted for Publishing in MNRAS (corrected PDF

Passivity-Based Control

Stabilization of physical systems by shaping their energy function is a well-established technique whose roots date back to the work of Lagrange and Legendre. Potential energy shaping for fully actuated mechanical systems was first introduced in Takegaki and Arimoto (Trans ASME J Dyn Syst Meas Control 12:119--125, 1981) more than 30 years ago. In Ortega and Spong (Automatica 25(6):877--888, 1989) it was proved that passivity was the key property underlying the stabilization mechanism of these designs, and the, now widely popular, term of passivity-based control was coined. In this chapter we summarize the basic principles and some of the main developments of this controller design technique

Hormonal regulation of female reproduction

Reproduction is an event that requires the coordination of peripheral organs with the nervous system to ensure that the internal and external environments are optimal for successful procreation of the species. This is accomplished by the hypothalamic-pituitary-gonadal axis that coordinates reproductive behavior with ovulation. The primary signal from the central nervous system is gonadotropin-releasing hormone (GnRH), which modulates the activity of anterior pituitary gonadotropes regulating follicle stimulating hormone (FSH) and luteinizing hormone (LH) release. As ovarian follicles develop they release estradiol, which negatively regulates further release of GnRH and FSH. As estradiol concentrations peak they trigger the surge release of GnRH, which leads to LH release inducing ovulation. Release of GnRH within the central nervous system helps modulate reproductive behaviors providing a node at which control of reproduction is regulated. To address these issues, this review focuses on several critical questions. How is the HPG axis regulated in species with different reproductive strategies? What internal and external conditions modulate the synthesis and release of GnRH? How does GnRH modulate reproductive behavior within the hypothalamus? How does disease shift the activity of the HPG axis.Fil: Christensen, A.. University of California at Los Angeles; Estados UnidosFil: Bentley, G. E.. University of California at Berkeley; Estados UnidosFil: Cabrera Kreiker, Ricardo Jorge. Universidad de Mendoza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Ortega, Hugo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Litoral; ArgentinaFil: Perfito, N.. University of California at Berkeley; Estados UnidosFil: Wu, T. J.. Uniformed Services University Of The Health Sciences; Estados UnidosFil: Micevych, P.. University of California at Los Angeles; Estados Unido

Solubility of three natural compounds with insecticidal activity in supercritical carbon dioxide: Experimental measurements and predictive modeling with the GC-EoS

In this work, the solubility of thymoquinone, R-(+)-pulegone and 1-octen-3-ol in supercritical CO2 is determined in a range of conditions typical of supercritical fluid processes such as extraction, fractionation and impregnation. These compounds were selected based in their insecticidal activity which may enable to apply them as biopesticides. Solubility was measured using a semicontinuos method in the temperature range of 45–65 °C and pressure of 8–12 MPa, at a CO2 flowrate of 0.05–0.10 g/min, which was verified to be low enough to ensure saturation. Solubilities were predicted using the Group Contribution Equation of State (GC-EoS) and compared to the experimental results, with a good agreement. Consistency of the data was tested using the density-based Chrastil equation

Quasi-normal modes, area spectra and multi-horizon spacetimes

We suggest an interpretation for the highly damped QNM frequencies of the spherically symmetric multi-horizon spacetimes (Reissner-Nordstrom, Schwarzschild-deSitter, Reissner-Nordstrom-deSitter) following Maggiore's proposal about the link between the asymptotic QNM frequencies and the black hole thermodynamics. We show that the behavior of the asymptotic frequencies is easy to understand if one assumes that all of the horizons have the same equispaced area spectra. The QNM analysis is then consistent with the choice of the area spectra to be the one originally proposed for the black hole's horizon by Bekenstein: A=8\pi n (in Planck units). The interpretation of the highly damped QNM frequencies in the multi-horizon case is based on the similar grounds as in the single horizon (Schwarzschild) case, but it has some new features that are discussed in the paper.Comment: 8 pages, v2: no physics changed, some references added, few sentences added in the discussion part

Prediction of stillbirth from maternal factors, fetal biometry and uterine artery Doppler at 19-24 weeks

Objectives: To evaluate the performance of screening for all stillbirths and those due to impaired placentation and unexplained or other causes by a combination of maternal factors, fetal biometry and uterine artery pulsatility index (UT-PI) at 19-24 weeks’ gestation and compare this performance to that of screening by UT-PI alone. Methods: This was a prospective screening study of 70,003 singleton pregnancies including 69,735 live births and 268 (0.38%) antepartum stillbirths; 159 (59%) were secondary to impaired placentation and 109 (41%) were due to other or unexplained causes. Multivariate logistic regression analysis was used to develop a model for prediction of stillbirth based on a combination of maternal factors, fetal biometry and UT-PI. Results: Combined screening predicted 55% of all stillbirths, including 75% of those due to impaired placentation and 23% of those that were due to other causes or unexplained, at false positive rate of 10%; within the impaired placentation group the detection rate of stillbirth at 37 weeks (88% vs 46%; p<0.001). The performance of screening by the combined test was superior to that of selecting the high-risk group on the basis of UT-PI being above the 90th percentile for gestational age, which predicted 48% of all stillbirths, 70% of those due to impaired placentation and 15% of those that were due to other causes or unexplained. Conclusions: Second-trimester screening by a combination of UT-PI with maternal factors and fetal biometry can predict a high proportion of stillbirths and in particular those due to impaired placentation

Simulation of the spreading of a gas-propelled micro-droplet upon impact on a dry surface using a lattice-Boltzmann approach

Spray cooling is one of the most promising methods of cooling high heat flux electronics. Depending on the type of the nozzle, spray cooling can be categorized as single phase or two phase. In the latter, which is known to be more effective, a secondary gas is used to further pressurize the liquid and form smaller droplets at higher velocities. The gas is also assumed to assist the spreading phase by imposing normal and tangential forces on the droplet free surface which adds to the complicated hydrodynamics of the droplet impact. Moreover, the order of magnitude of droplet size in spray cooling is 10¯⁶m thereby introducing a low Weber and Reynolds numbers impact regime which heretofore has not been well understood. A 3D lattice Boltzmann method was implemented to simulate the impact of a single micro-droplet on a dry surface in both ambient air and under a stagnation gas flow. Two cases were closely compared and correlations were proposed for the instantaneous spreading diameter. Contrary to recent findings at higher impact We and Re, it was found that stagnation flow only significantly affects the spreading phase for Ca*⩾0.35 but has little influence on the receding physics