Discrete Variational Optimal Control

This paper develops numerical methods for optimal control of mechanical systems in the Lagrangian setting. It extends the theory of discrete mechanics to enable the solutions of optimal control problems through the discretization of variational principles. The key point is to solve the optimal control problem as a variational integrator of a specially constructed higher-dimensional system. The developed framework applies to systems on tangent bundles, Lie groups, underactuated and nonholonomic systems with symmetries, and can approximate either smooth or discontinuous control inputs. The resulting methods inherit the preservation properties of variational integrators and result in numerically robust and easily implementable algorithms. Several theoretical and a practical examples, e.g. the control of an underwater vehicle, will illustrate the application of the proposed approach.Comment: 30 pages, 6 figure

Interacting color strings as the origin of the liquid behavior of the quark-gluon plasma

We study the radial distribution function of the color sources (strings) formed in hadronic collisions and the requirements to obtain a liquid. As a repulsive interaction is needed, we incorporate a concentric core in the strings as well as the probability that a string allows core-core overlaps. We find systems where the difference between the gas-liquid and confined-deconfined phase transition temperatures is small. This explains the experimentally observed liquid behavior of the quark-gluon plasma above the confineddeconfined transition temperature.J. E. R. acknowledges financial support from Consejo Nacional de Ciencia y Tecnología (postdoctoral fellowship Grant No. 289198). B. D. was partially supported by a DGAPA-UNAM postdoctoral fellowship and acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement No. 801538. C. P. has received financial support from Xunta de Galicia (Centro singular de investigación de Galicia), by European Union ERDF, and by the “María de Maeztu” Units of Excellence program MDM-2016-0692 and the Spanish Research State Agency. We thank Nestor Armesto and David Vergara for their valuable comments. J. E. R. acknowledges financial support from Consejo Nacional de Ciencia y Tecnología (postdoctoral fellowship Grant No. 289198). B. D. was partially supported by a DGAPA-UNAM postdoctoral fellowship and acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement No. 801538. C. P. has received financial support from Xunta de Galicia (Centro singular de investigación de Galicia), by European Union ERDF, and by the “María de Maeztu” Units of Excellence program MDM-2016-0692 and the Spanish Research State Agency. We thank Nestor Armesto and David Vergara for their valuable comments.Publicad

Localization processes for functional data analysis

We propose an alternative to k-nearest neighbors for functional data whereby the approximating neighboring curves are piecewise functions built from a functional sample. Using a locally defined distance function that satisfies stabilization criteria, we establish pointwise and global approximation results in function spaces when the number of data curves is large. We exploit this feature to develop the asymptotic theory when a finite number of curves is observed at time-points given by an i.i.d. sample whose cardinality increases up to infinity. We use these results to investigate the problem of estimating unobserved segments of a partially observed functional data sample as well as to study the problem of functional classification and outlier detection. For such problems our methods are competitive with and sometimes superior to benchmark predictions in the field. The R package localFDA provides routines for computing the localization processes and the estimators proposed in this article

Can low-cost road vehicles positioning systems fulfil accuracy specifications of new ADAS applications?

Some new Advanced Driver Assistance Sy stems (ADAS) need on-the-lane vehicle positioning on accurate digital maps, but present applications of vehicle positioning do not justify the surcharge of very ac curate equipment such as DGPS or high-cost inertial systems. For this reason, performance of GPS in autonomous mode is analyzed. Although satisfactory results can be found, in some areas GPS signal is lost or degraded, so it is necessary to know the positioning error when using only inertial system data. A th eoretical approach based on the uncertainty propagation law is used to esti mate the upper limit of distance that can be travelled fulfilling the specifications of an assistance system. Tests results support the conclusions of this approach. Finally, the comb ination of GPS and inertial systems is studied, resulting that the theoretical approach is valid when inertial measurements are used right from the start of GPS signal de gradation, without waiting for a complete loss.The work reported in this paper has been partly funded by the Spanish Ministry of Science and Innovation (SIAC project TRA2007-67786-C02-01 and TRA2007-67786-C02-02) and the CAM project SEGVAUTO.Publicad

La seca de encinas y alcornoques en Andalucía : decaimiento y enfermedad

El decaimiento forestal es una enfermedad de etiología compleja, resultado de la acción de un número variable de factores bióticos y abióticos que causan un deterioro gradual y general de los árboles afectados, hasta su muerte. Los factores implicados en el decaimiento de los Quercus en Andalucía son factores predisponentes de tipo selvícola, alteraciones climáticas como factor incitante, y plagas y enfermedades como factores contribuyentes. Entre las enfermedades implicadas en Seca de los Quercus destacan, por orden de importancia, la podredumbre radical causada por Phytophthora cinnamomi, los chancros de tronco y ramas causados por Botryosphaeria spp. y el chancro carbonoso causado por Biscogniauxia mediterranea. No obstante, las dos primeras enfermedades tienen una especial incidencia en distintas zonas de Andalucía de forma independiente, no asociadas al decaimiento. En el presente artículo se exponen las medidas de control disponibles contra estas enfermedades de los Quercus y se plantea la necesidad de disponer de un diagnóstico preciso en cada caso para abordar dicho control con garantías, ya que no cabe encontrar soluciones únicas que resulten eficaces con independencia de la naturaleza del problema._____________________________________The forestry decline is a complex disease, as a result of the action of a changeable number of biotic and abiotic factors that cause a gradual and general deterioration of the affected trees, until their death. The factors involved in the Quercus decline in Andalusia are predisposing factors like silvic, climatic alterations as inciting factor, and insect pest and diseases as contributing factors. Between the diseases involved in oak decline stand out, in order of importance, the root roting caused by Phytophthora cinnamomi, the chancres of trunk and branches caused by Botryosphaeria spp. and the charcoal canker caused by Biscogniauxia mediterranea. Nevertheless, the first two diseases have a special effect on different zones of Andalusia in different ways, not associated with the decay. In this article we expose the available tools of disease control. We emphasizes the need of having a precise diagnosis in every case to approach the control with guarantees, since there is no chance of finding only one efficient solution regardless of the nature of the problem

Developmental changes in the relations between RAN, phonological awareness, and reading in Spanish children

We examined the developmental relations of phonological awareness (PA) and rapid automatized naming (RAN) with reading in a cross-sectional study with 874 Spanish children from Grades 2 to 6. Our main prediction was that the RAN-reading relationship would decrease due to a gradual change in reading strategy, from serial decoding to sight word reading. Therefore, in contrast to most previous studies, we used discrete reading tasks. Serial RAN tasks for objects, colors, digits, and letters were included. First, we examined whether the RAN tasks loaded on the same constructs across time. An alphanumeric and a nonalphanumeric factor were identified, which were invariant over time. In subsequent multigroup structural equation models we found that the PA-reading relationship was low but slightly increased in the higher grades. As predicted, the RAN-reading relationship decreased for words, whereas the relationship remained stable for pseudowords

Predictive Psychosocial Factors of Child-to-Parent Violence in a Sample of Mexican Adolescents

The aim of this study was to carry out a psychosocial analysis of child-to-parent violence (CPV) in a sample of school adolescents, considering a set of individual variables (psychological distress, problematic use of social networking sites, and perceived non-conformist social reputation) and family variables (open and problematic communication with parents) according to sex. The sample consisted of 3, 731 adolescents (54% boys), aged between 14 and 16 years (M = 14.6 years, SD = 0.567), from the state of Nuevo León, Mexico. The scores of the boys and girls were analyzed to check for differences. Also, correlations between all the study variables were calculated. Finally, a multiple stepwise regression analysis was carried out for the total sample and also for boys and girls separately. Results confirmed the important role of individual variables as predictors of CPV in boys and girls. The main difference between boys and girls was observed in the predictive weight of problematic use of social networking sites, which was higher in girls than in boys. Open communication with the father was a significant factor for predicting the decrease of CPV levels in the case of boys, while open communication with the mother predicted the decrease of CPV in girls. Problematic communication with the mother showed similar values in boys and girls when predicting CPV, however, the predictive weight of problematic communication with the father was higher in girls than in boys. These results are interesting and have important implications for the prevention of CPV

Specification and Development of a HMI for ADAS, Based in Usability and Accessibility Principles

Traditionally, the design of road vehicle HMI is based in esthetic principles, maintaining it as an attractive factor for possible clients when buying a car. Only recently, ergonomic benefits have been applied to the design of HMIs, mainly following institutional impulses like the European Union one, but whose contribution is not clearly stated nowadays in commercial products. In this paper the authors present a study of the design of an HMI, based in usability and accessibility premises, centering the design in the user, as method to improve safety, making natural the communication with the driver as well as being able to transmitting information to the driver, from basic to the generated by ADAS installed in the car. Following these specifications a set of prototypes have been designed in order to develop a testbed that could be evaluated for a large set of drivers.This work has been supported by the Spanish Ministry of Science and Innovation (TRA2007-67786 and TRA2009-07505) and the CAM project SEGVAUTO-II.Publicad