Algebraic Invariance Conditions in the Study of Approximate (Null-)Controllability of Markov Switch Processes

We aim at studying approximate null-controllability properties of a particular class of piecewise linear Markov processes (Markovian switch systems). The criteria are given in terms of algebraic invariance and are easily computable. We propose several necessary conditions and a sufficient one. The hierarchy between these conditions is studied via suitable counterexamples. Equivalence criteria are given in abstract form for general dynamics and algebraic form for systems with constant coefficients or continuous switching. The problem is motivated by the study of lysis phenomena in biological organisms and price prediction on spike-driven commodities.Comment: Mathematics of Control, Signals, and Systems, Springer Verlag (Germany), 2015, online first http://link.springer.com/article/10.1007/s00498-015-0146-

A scheme for simulating one-dimensional diffusion processes with discontinuous coefficients

The aim of this article is to provide a scheme for simulating diffusion processes evolving in one-dimensional discontinuous media. This scheme does not rely on smoothing the coefficients that appear in the infinitesimal generator of the diffusion processes, but uses instead an exact description of the behavior of their trajectories when they reach the points of discontinuity. This description is supplied with the local comparison of the trajectories of the diffusion processes with those of a skew Brownian motion.Comment: Published at http://dx.doi.org/10.1214/105051605000000656 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

A Piecewise Deterministic Markov Toy Model for Traffic/Maintenance and Associated Hamilton-Jacobi Integrodifferential Systems on Networks

We study optimal control problems in infinite horizon when the dynamics belong to a specific class of piecewise deterministic Markov processes constrained to star-shaped networks (inspired by traffic models). We adapt the results in [H. M. Soner. Optimal control with state-space constraint. II. SIAM J. Control Optim., 24(6):1110.1122, 1986] to prove the regularity of the value function and the dynamic programming principle. Extending the networks and Krylov's ''shaking the coefficients'' method, we prove that the value function can be seen as the solution to a linearized optimization problem set on a convenient set of probability measures. The approach relies entirely on viscosity arguments. As a by-product, the dual formulation guarantees that the value function is the pointwise supremum over regular subsolutions of the associated Hamilton-Jacobi integrodifferential system. This ensures that the value function satisfies Perron's preconization for the (unique) candidate to viscosity solution. Finally, we prove that the same kind of linearization can be obtained by combining linearization for classical (unconstrained) problems and cost penalization. The latter method works for very general near-viable systems (possibly without further controllability) and discontinuous costs.Comment: accepted to Applied Mathematics and Optimization (01/10/2015

INSA scientific activities in the space astronomy area

Support to Astronomy operations is an important and long-lived activity within INSA. Probably the best known (and traditional) INSA activities are those related with real-time spacecraft operations: Ground station maintenance and operation (Ground station engineers and operators); spacecraft and payload real-time operation (spacecraft and instruments controllers); computing infrastructure maintenance (operators, analysts) and general site services.In this paper, we'll show a different perspective, probably not so well-known, presenting some INSA recent activities at the European Space Astronomy Centre (ESAC) and NASA Madrid Deep Space Communication Complex (MDSCC) directly related to scientific operations. Basic lines of activity involved include: Operations support for science operations; system and software support for real time systems; technical administration and IT support; R \& D activities, radioastronomy (at MDSCC and ESAC) and scientific research projects. This paper is structured as follows: first, INSA activities in two ESA cornerstone astrophysics missions, XMM-Newton and Herschel, will be outlined. Then, our activities related to Science infrastructure services, represented by the Virtual Observatory (VO) framework and the Science Archives development facilities are briefly shown. Radio Astronomy activities will be described afterwards, and finally, a few research topics in which INSA scientists are involved will be also described.Comment: 6 pages. Highlights of Spanish Astrophysics V Proceedings of the VIII Scientific Meeting of the Spanish AstronomicalSociety (SEA) held in Santander, 7-11 July, 200

Elaboración y caracterización de concreto polimérico: efecto del contenido de fibra de luffa y de la radiación gamma

A pesar de que el concreto convencional (elaborado con cemento Portland) es un material con gran versatilidad en cuanto a su funcionalidad y economía, presenta algunas limitaciones tales como: alta porosidad y baja resistencia a esfuerzos de flexión, tensión y a reactivos químicos altamente corrosivos. Algunas de estas limitaciones se han subsanado mediante la incorporación de fibras. Se han podido mejorar la resistencia a la tracción, compresión, durabilidad, resistencia a la fatiga, resistencia al impacto y a la abrasión, la contracción, la expansión, la estabilidad térmica, y resistencia al fuego. Sin embargo, muy pocas investigaciones ha abordado el efecto de fibras en concreto poliméricoEn el presente trabajo se estudian los efectos de la incorporación de fibras y de la radiación gamma en las propiedades mecánicas del concreto polimérico, en particular las resistencias a la compresión y a la flexión, la deformación mecánica y los módulos de elasticidad. Los concretos son elaborados con resina de poliéster insaturada, arena sílice y fibras de Luffa como agregados.CONACY

Payments for Environmental Services in Watersheds: Insights From a Comparative Study of three Cases in Central America

We have compared three cases of payments for water-related environmental services (PES) in Central America, in terms of socioeconomic background, opportunity costs of forest conservation and stakeholders’ perceptions on the conditions of water resources and other issues. We found that, in general, the foregone benefits from land uses alternative to forest cover are larger than the amount paid, which apparently contradicts the economic foundation of PES schemes. A number of possible explanations are explored. The results also suggest that trade-offs between different environmental and social goals are likely to emerge in PES schemes, posing some doubts on their ability to be multipurpose instruments for environmental improvement and rural development. We also found that PES schemes may work as a conflictresolution instrument, facilitating downstream -upstream problem solving, though at the same time they might introduce changes in social perceptions of property rights.environmental services, watershed management, rural development, property rights, Honduras, Costa Rica, Nicaragua.

Liquid-crystal patterns of rectangular particles in a square nanocavity

Using density-functional theory in the restricted-orientation approximation, we analyse the liquid-crystal patterns and phase behaviour of a fluid of hard rectangular particles confined in a two-dimensional square nanocavity of side length $H$ composed of hard inner walls. Patterning in the cavity is governed by surface-induced order, capillary and frustration effects, and depends on the relative values of particle aspect ratio $\kappa\equiv L/\sigma$, with $L$ the length and $\sigma$ the width of the rectangles ($L\ge\sigma$), and cavity size $H$. Ordering may be very different from bulk ($H\to\infty$) behaviour when $H$ is a few times the particle length $L$ (nanocavity). Bulk and confinement properties are obtained for the cases $\kappa=1$, 3 and 6. In the confined fluid surface-induced frustration leads to four-fold symmetry breaking in all phases (which become two-fold symmetric). Since no director distorsion can arise in our model by construction, frustration in the director orientation is relaxed by the creation of domain walls (where the director changes by $90^{\circ}$); this configuration is necessary to stabilise periodic phases. For $\kappa=1$ the crystal becomes stable with commensuration transitions taking place as $H$ is varied. In the case $\kappa=3$ the commensuration transitions involve columnar phases with different number of columns. Finally, in the case $\kappa=6$, the high-density region of the phase diagram is dominated by commensuration transitions between smectic structures; at lower densities there is a symmetry-breaking isotropic $\to$ nematic transition exhibiting non-monotonic behaviour with cavity size.Comment: 31 pages, 15 figure

Simulating Spiking Neural P systems without delays using GPUs

We present in this paper our work regarding simulating a type of P system known as a spiking neural P system (SNP system) using graphics processing units (GPUs). GPUs, because of their architectural optimization for parallel computations, are well-suited for highly parallelizable problems. Due to the advent of general purpose GPU computing in recent years, GPUs are not limited to graphics and video processing alone, but include computationally intensive scientific and mathematical applications as well. Moreover P systems, including SNP systems, are inherently and maximally parallel computing models whose inspirations are taken from the functioning and dynamics of a living cell. In particular, SNP systems try to give a modest but formal representation of a special type of cell known as the neuron and their interactions with one another. The nature of SNP systems allowed their representation as matrices, which is a crucial step in simulating them on highly parallel devices such as GPUs. The highly parallel nature of SNP systems necessitate the use of hardware intended for parallel computations. The simulation algorithms, design considerations, and implementation are presented. Finally, simulation results, observations, and analyses using an SNP system that generates all numbers in $\mathbb N$ - {1} are discussed, as well as recommendations for future work.Comment: 19 pages in total, 4 figures, listings/algorithms, submitted at the 9th Brainstorming Week in Membrane Computing, University of Seville, Spai

Re-signifying the Subject Positions of the Observers. the narrated experiences of ELT class Observers in Colombia

Esta tesis doctoral evidencia un análisis cuidadoso de las posiciones de los observadores en las clases de inglés. El tema se centra en las observaciones de las clases de inglés, principalmente desde las posiciones de los Observadores que supervisan, evalúan y retroalimentan a los profesores de inglés. En el campo ELT (Enseñanza del Idioma Inglés), es común que los maestros sean observados periódicamente durante las clases para determinar su desempeño en la instrucción. De hecho, algunos de ellos no están de acuerdo con el proceso de observación de clase. Otros sostienen que el proceso de observación no es necesario ni importante. Algunos incluso no prestan atención a la persona que observa la clase y solo tienen presente las rúbricas utilizadas para observar. Este estudio identifica algunas posiciones de los observadores que son ignoradas o invisibilizadas en la comunidad educativa.This doctoral thesis demonstrates a careful analysis of the observers’ positions in English language classes. The topic focuses on the observations of in-service English classes, mainly from the Positions of the Observers who supervise, evaluate, and give feedback to English language teachers. In the ELT (English Language Teaching) field, it is common that teachers are periodically observed during classes for their performance of instruction. In fact, some of them do not agree with the class observation process. Others argue that the observation process is not necessary nor important. Some even do not pay attention to the person who observes the class and only keep in mind the rubrics used to observe. This study identifies some positions of the observers that are overlooked or are invisible in the educational community