Prices are macro-observables! Stylized facts from evolutionary finance

Prices are macro-observables of a financial market that result from the trading actions of a huge number of individual investors. Major stylized facts of empirical asset returns concern (i) non-Gaussian distribution of empirical asset returns and (ii) volatility clustering, i.e., the slow decay of auto- correlations of absolute returns. We propose a model for the aggregate dynamics of the market which is generated by the coupling of a ‘slow' and a ‘fast' dynamical component, where the ‘fast' component can be seen as a perturbation of the ‘slow' one. Statistical properties of price changes in this model are estimated by simulation; sample size is 4× 106. It is shown that increasing the decoupling of these two dynamical levels generates a crossover in the distribution of log returns from a concave Gaussian-like distribution to a convex, truncated Levy-like one. For a sufficiently large degree of dynamic decoupling, the return trails exhibit pronounced volatility clusterin

Nanoestructuras, ablación láser y fotoacústica

Describe el equipo del laboratorio de Fotofísica del Centro de Ciencias Aplicadas y Desarrollo Tecnológico de la Universidad Nacional Autónoma de México (UNAM). Asimismo, define las nanoestructuras, la irradiación con láser y la técnica fotoacústica

Microstructure and composition design of magnetic Ni-Mn-Sn Co-sputter deposited films

"In this work, we study the effect of the substrate temperature (ST) during sputter-deposition as well as co-sputtering deposition on the fabrication of nanostructured Ni-Mn-Sn thin films. Sputtered films show Mn losses of around 10 at.% while the average grain size () increased from 30 nm to 105 nm with the increasing of ST. Mn losses compensation is proposed by co-sputtered deposition. With such a purpose a variable electrical power was applied to the radio frequency (RF) Mn cathode. By increasing the electrical power applied to the RF Mn cathode both Mn and Ni contents approach to the targeted nominal composition Ni:Mn:Sn = 50:37:13. Elemental chemical composition analyses show that the composition varied between Ni61.5Mn26.2Sn12.3 and Ni54.6Mn30.5Sn14.9 when the applied RF-power increased from 0 W to 30 W.

APLICACIÓN DE UN REGULADOR H-INFINITO NO LINEAL PARA GRÚA 3D (APPLICATION OF A NONLINEAR H-INFINITY REGULATOR FOR A 3D-CRANE)

ResumenEn este artículo se presenta la solución al problema de estabilizacion de posición robusta ante perturbaciones externas de una grúa a través de un regulador H-infinito no lineal. La grúa bajo estudio en un sistema mecánico subactuado de cinco grados de libertad y tres actuadores que manipulan el movimiento de la cuerda a través de un carro que se mueve en el plano cartesiano. Las posiciones de los actuadores y los ángulos de la cuerda que transporta la carga se pueden medir únicamente mientras que sus velocidades se estiman a través de un filtro H-infinito. Por naturaleza, la carga se encuentra sujeta a perturbaciones externas que se asumen pertenecen al espacio . La solución al problema de control H-infinito por retroalimentación de salida involucra la solución a un par de ecuaciones algebraicas perturbadas de Riccati que evitan hacer la verificación de controlabilidad y detectabilidad del sistema. Los resultados experimentales, realizados en una grúa didáctica, demuestran la factibilidad del método.Palabras claves: Grúa, regulador H-infinito no lineal, robustez.   AbstractIn this paper we present the solution to the robust position stabilization against external disturbances of a crane by using a nonlinear H-infinity regulator. The crane under study is an underactuated mechanical system of five degrees-of-freedom and three actuators that manipulate the rope through a cart moving along the Cartesian space. The position of the cart and the angles of the rope are the only available measurements for feedback while its velocities are estimated by using an H-infinity filter. Typically, the rope is affected by external disturbances which are assumed belong to the  space. The solution of the H-infinity regulator involves the solution of two perturbed algebraic Riccati equations which avoid the verification of the controllability and detectability of the system. The experimental results, made in a laboratory crane, demonstrate the effectiveness of the proposed method.Keywords: Crane, nonlinear H-infinity regulator, robustness

ESTIMACIÓN DE LOS COEFICIENTES DE INERCIA Y DE FRICCIÓN DE UN MOTOR DE CD (ESTIMATION OF INERTIA AND FRICTION COEFFICIENTS OF A DC MOTOR)

ResumenEn este trabajo se presentan algunos modelos de fricción, y se destaca la importancia de los parámetros de fricción viscosa y de Coulomb, los cuales son necesarios para definir los distintos modelos que describen el comportamiento de la fricción en sistema mecánicos. Se describen los métodos de torque constante y entrada tipo rampa para estimar los coeficientes de fricción viscosa y de Coulomb, estos métodos se aplican en un motor de CD para obtener sus parámetros. A fin de comprobar que los parámetros estimados son los adecuados, se diseña y se aplica un control de velocidad, utilizando un controlador proporcional con compensación. La estimación de los parámetros y el control de velocidad del motor se realiza de forma experimental utilizando una plataforma de Arduino UNO en conjunto con la herramienta de Simulink de MatLab. Los resultados muestran que los coeficientes de fricción estimados son adecuados.Palabras Claves: control, estimación, fricción, motor de cd. AbstractIn this paper, some friction models are presented, highlighting the importance of viscous and Coulomb friction parameters, which are necessary to define the different models that describe the friction behavior in mechanical systems. The constant torque and ramp-type input methods for estimating viscous and Coulomb friction coefficients are described. These methods are applied in a DC motor, and their parameters are obtained. To verify that the estimated parameters are adequate, a speed control is designed and applied, using a proportional controller with compensation. Parameter estimation and motor speed control is performed experimentally using an Arduino UNO platform together with Simulink tool of MatLab. The results show that the estimated friction parameters are adequate.Keywords: control, friction, measurement, dc motor

A brief review of research using near-infrared spectroscopy to measure activation of the prefrontal cortex during emotional processing : the importance of experimental design

During the past two decades there has been a pronounced increase in the number of published research studies that have employed near-infrared spectroscopy (NIRS) to measure neural activation. The technique is now an accepted neuroimaging tool adopted by cognitive neuroscientists to investigate a number of fields, one of which is the study of emotional processing. Crucially, one brain region that is important to the processing of emotional information is the prefrontal cortex (PFC) and NIRS is ideally suited to measuring activity in this region. Compared to other methods used to record neural activation, NIRS reduces the discomfort to participants, makes data collection from larger sample sizes more achievable, and allows measurement of activation during tasks involving physical movement. However, the use of NIRS to investigate the links between emotion and cognition has revealed mixed findings. For instance, whilst some studies report increased PFC activity associated with the processing of negative information, others show increased activity in relation to positive information. Research shows differences in PFC activity between different cognitive tasks, yet findings also vary within similar tasks. This work reviews a selection of recent studies that have adopted NIRS to study PFC activity during emotional processing in both healthy individuals and patient populations. It highlights the key differences between research findings and argues that variations in experimental design could be a contributing factor to the mixed results. Guidance is provided for future work in this area in order to improve consistency within this growing field