Integral Resonant Control for vibration damping and precise tip-positioning of a single-link flexible manipulator

Peer reviewedPostprin

Functional Optimisation of Online Algorithms in Multilayer Neural Networks

We study the online dynamics of learning in fully connected soft committee machines in the student-teacher scenario. The locally optimal modulation function, which determines the learning algorithm, is obtained from a variational argument in such a manner as to maximise the average generalisation error decay per example. Simulations results for the resulting algorithm are presented for a few cases. The symmetric phase plateaux are found to be vastly reduced in comparison to those found when online backpropagation algorithms are used. A discussion of the implementation of these ideas as practical algorithms is given

Spectral and correlation properties of rings of delay-coupled elements:Comparing linear and nonlinear systems

The dynamical properties of delay-coupled systems are currently of great interest. So far the analysis has concentrated primarily on identical synchronization properties. Here we study the dynamics of rings of delay-coupled nodes, a topology that cannot show identical synchronization, and compare its properties to those of linear stochastic maps. We find that, in the long delay limit, the correlation functions and spectra of delay-coupled rings of nonlinear systems obey the same scaling laws as linear systems, indicating that important properties of the emerging solution result from network topology

Amplitude and phase effects on the synchronization of delay-coupled oscillators

We consider the behavior of Stuart-Landau oscillators as generic limit-cycle oscillators when they are interacting with delay. We investigate the role of amplitude and phase instabilities in producing symmetry-breaking/restoring transitions. Using analytical and numerical methods we compare the dynamics of one oscillator with delayed feedback, two oscillators mutually coupled with delay, and two delay-coupled elements with self-feedback. Taking only the phase dynamics into account, no chaotic dynamics is observed, and the stability of the identical synchronization solution is the same in each of the three studied networks of delay-coupled elements. When allowing for a variable oscillation amplitude, the delay can induce amplitude instabilities. We provide analytical proof that, in case of two mutually coupled elements, the onset of an amplitude instability always results in antiphase oscillations, leading to a leader-laggard behavior in the chaotic regime. Adding self-feedback with the same strength and delay as the coupling stabilizes the system in the transverse direction and, thus, promotes the onset of identically synchronized behavior

Dynamical transitions in the evolution of learning algorithms by selection

We study the evolution of artificial learning systems by means of selection. Genetic programming is used to generate a sequence of populations of algorithms which can be used by neural networks for supervised learning of a rule that generates examples. In opposition to concentrating on final results, which would be the natural aim while designing good learning algorithms, we study the evolution process and pay particular attention to the temporal order of appearance of functional structures responsible for the improvements in the learning process, as measured by the generalization capabilities of the resulting algorithms. The effect of such appearances can be described as dynamical phase transitions. The concepts of phenotypic and genotypic entropies, which serve to describe the distribution of fitness in the population and the distribution of symbols respectively, are used to monitor the dynamics. In different runs the phase transitions might be present or not, with the system finding out good solutions, or staying in poor regions of algorithm space. Whenever phase transitions occur, the sequence of appearances are the same. We identify combinations of variables and operators which are useful in measuring experience or performance in rule extraction and can thus implement useful annealing of the learning schedule.Comment: 11 pages, 11 figures, 2 table

Characterizing entanglement with geometric entanglement witnesses

We show how to detect entangled, bound entangled, and separable bipartite quantum states of arbitrary dimension and mixedness using geometric entanglement witnesses. These witnesses are constructed using properties of the Hilbert-Schmidt geometry and can be shifted along parameterized lines. The involved conditions are simplified using Bloch decompositions of operators and states. As an example we determine the three different types of states for a family of two-qutrit states that is part of the "magic simplex", i.e. the set of Bell-state mixtures of arbitrary dimension.Comment: 19 pages, 4 figures, some typos and notational errors corrected. To be published in J. Phys. A: Math. Theo

An information theoretic approach to statistical dependence: copula information

We discuss the connection between information and copula theories by showing that a copula can be employed to decompose the information content of a multivariate distribution into marginal and dependence components, with the latter quantified by the mutual information. We define the information excess as a measure of deviation from a maximum entropy distribution. The idea of marginal invariant dependence measures is also discussed and used to show that empirical linear correlation underestimates the amplitude of the actual correlation in the case of non-Gaussian marginals. The mutual information is shown to provide an upper bound for the asymptotic empirical log-likelihood of a copula. An analytical expression for the information excess of T-copulas is provided, allowing for simple model identification within this family. We illustrate the framework in a financial data set.Comment: to appear in Europhysics Letter

Efectividad de la terapia combinada a dosis fijas en una cohorte de hipertensos no controlados con monoterapia

ObjetivoEvaluar la efectividad de lisinoprilhidroclorotiazida a dosis fijas en el control de la presión arterial en hipertensos tratados con monoterapia y mal controlados.DiseñoEstudio observacional, prospectivo.EmplazamientoAtención primaria.ParticipantesCiento noventa y nueve médicos de atención primaria que incluyeron a 931 pacientes (56,7% mujeres), con edad media de 62,0 ± 10,3 años. Finalizaron el estudio 915 pacientes (98%) que se incluyeron en el análisis.Mediciones principalesSe siguieron las recomendaciones de la OMS/SIH en la medición de la presión arterial y el diagnóstico de mal control. Además, se evaluaron presión del pulso, índice de masa corporal y parámetros analíticos básicos. Se realizaron 4 visitas durante 6 meses de seguimiento.ResultadosLisinopril-hidroclorotiazida (20/12,5mg) disminuyó significativamente la PAS (24,6 ± 3,5mmHg) y la PAD (14,3 ± 0,7mmHg) (p < 0,001). El control de la presión arterial aumentó hasta el 52,8% (p < 0,001). La edad fue la única variable que influyó en el control de la presión arterial (OR, 0,81; IC del 95%, 0,71-0,92%; p = 0,001). La presión del pulso disminuyó 10,4 ± 4,3mmHg (p < 0,001). A las 24 semanas de tratamiento, se observó una mejoría en el perfil glucémico y lipídico, y de la HbA1c en los diabéticos.ConclusionesEn atención primaria, lisinopril-hidroclorotiazida (20/12,5mg), controló la presión arterial del 52,8% los de hipertensos mal controlados con monoterapia. Además, disminuyó la presión del pulso y mejoró el perfil lipídico y el glucémico.ObjectiveTo evaluate the effectiveness of the fixed dose of a lisinoprilhydrochlorothiazide combination treatment in the control of blood pressure, in poorly controlled high blood pressure people, treated with monotherapy.DesignProspective observational study.SettingPrimary care frame.Participants931 patients (56.7% women) with an average age of 62.0±10.3 years, were included by 199 primary care physicians. 915 patients (98%) ended the study and finally they were included for the statistical analysis.Main measurementsOMS/SIH recommendations on blood pressure measurement and diagnose of poor control were followed. Pulse pressure, body mass index and basic clinical analyses were assessed. Four continuation visits were made during six months.ResultsLisinopril–hidrochlorothiazide (20/12.5mg) reduced significantly SBP (24.6±3.5mm Hg) and DBP (14,3±0.7mm Hg) (P<.001). Blood pressure control was only influenced by age (OR, 0.81; 95% CI, 0.71-0.92; P=.001). Pulse pressure was reduced in 10.4±4.3mm Hg (P<.001). After 24 weeks of treatment, glycemic and lipidic profiles showed an improvement, as well as HbA1c in diabetic people.ConclusionsIn Primary care, a 52.8% of poorly controlled with monotherapy high blood pressure people were controlled by a combination of lisinoprilhydrochlorothiazide (20/12.5mg). In addition, pulse pressure was decreased and both lipid and glucose blood profiles improved

Transport coefficients for an inelastic gas around uniform shear flow: Linear stability analysis

The inelastic Boltzmann equation for a granular gas is applied to spatially inhomogeneous states close to the uniform shear flow. A normal solution is obtained via a Chapman-Enskog-like expansion around a local shear flow distribution. The heat and momentum fluxes are determined to first order in the deviations of the hydrodynamic field gradients from their values in the reference state. The corresponding transport coefficients are determined from a set of coupled linear integral equations which are approximately solved by using a kinetic model of the Boltzmann equation. The main new ingredient in this expansion is that the reference state $f^{(0)}$ (zeroth-order approximation) retains all the hydrodynamic orders in the shear rate. In addition, since the collisional cooling cannot be compensated locally for viscous heating, the distribution $f^{(0)}$ depends on time through its dependence on temperature. This means that in general, for a given degree of inelasticity, the complete nonlinear dependence of the transport coefficients on the shear rate requires the analysis of the {\em unsteady} hydrodynamic behavior. To simplify the analysis, the steady state conditions have been considered here in order to perform a linear stability analysis of the hydrodynamic equations with respect to the uniform shear flow state. Conditions for instabilities at long wavelengths are identified and discussed.Comment: 7 figures; previous stability analysis modifie

Avaliação das alterações na cobertura vegetal de área no Estado do Mato Grosso do Sul entre 1990 e 2010 por meio de imagens Landsat TM.

Imagens Landsat/TM dos anos de 1990 e 2010 de área no Estado de Mato Grosso do Sul foram transformadas em imagens de reflectância e classificadas quanto à presença, ao porte e à densidade de cobertura vegetal do solo, com base nos valores calculados de NDVI e de reflectância na banda do infravermelho próximo (&#961;ivp). Pela fusão digital das imagens classificadas de ambos os anos foi possível tipificar e quantificar as alterações ocorridas no período. Áreas da classe delimitada pelos valores de NDVI entre 0,55 e 0,75, associadas em sua maioria às pastagens, cobriam 60,2% da área de estudo em 1990 e 64,0% em 2010. As áreas da classe associada à vegetação densa com grande presença de espécies arbóreas (cerrado e matas de galeria) foram reduzidas de 31,1% para 24,5% no mesmo período, redução provocada, sobretudo, pelo aumento das áreas com pastagens. As lavouras com vegetação herbácea verde cobrindo completamente o solo na data de aquisição das imagens e algumas áreas de silvicultura foram associadas a valores de NDVI acima de 0,75 e &#961;ivp &#8805; 0,40 e totalizaram áreas equivalentes a 4,3% da área de estudo em 1990 e 2,2 % em 2010. As áreas com vegetação esparsa ou ausente compreendiam menos de 10% da área de estudo em ambos os anos, e normalmente estavam associadas a pastagens com sinais de degradação, locais destinados a lavouras, solo exposto, feições urbanas e corpos d?água