Impacto del efecto relativo de la edad y el género en la evaluación de la condición física en alumnos de secundaria.

El Efecto Relativo de la Edad (RAE) se refiere a la variabilidad en el potencial cognitivo y biológico, que aparece entre individuos agrupados por su edad cronológica, que provoca desigualdades en su rendimiento. El propósito de este estudio fue evaluar si la distribución de los nacimientos en el año y el género, afectan a la nota en Educación Física (EF) obtenida a través de test físicos. La nota de 252 alumnos (124 hombres y 128 mujeres) en los test físicos obtenidos en la asignatura de Educación Física, fue analizada formando 5 grupos de acuerdo al curso, divididos en cuatro cuartiles de nacimiento: a) Primer cuartil (Enero-Marzo); b) Segundo cuartil (Abril-Junio); c) Tercer cuartil (Julio-Septiembre); y d) Cuarto cuartil (Octubre-Diciembre) en cada una de las edades comprendidas entre 13 y 17 años. Aparecieron diferencias al comparar la nota en relación al cuartil de nacimiento (F(3, 24) = 5.39; p menor que .01; ?2 = .06 Potencia observada ß = .93) y respecto al género (F(1, 24) = 13.20; p menor que .01; ?2 = .05 Potencia observada ß = .95). Los resultados sugieren que existen diferencias en el rendimiento en las pruebas físicas en la asignatura de EF respecto al cuartil de nacimiento y al género. Basándose en la evidencia se podría sugerir la consideración por parte de los profesores de EF de estos resultados ya que las evaluaciones en Educación Física a través de test físicos podrían representar una desventaja a los alumnos nacidos en los meses finales del año. Al mismo tiempo diferencias de género aparecen al utilizar este tipo de evaluaciones.

On ergodic least-squares estimators of the generalized diffusion coefficient for fractional Brownian motion

We analyse a class of estimators of the generalized diffusion coefficient for fractional Brownian motion Bt of known Hurst index H, based on weighted functionals of the single time square displacement. We show that for a certain choice of the weight function these functionals possess an ergodic property and thus provide the true, ensemble-averaged, generalized diffusion coefficient to any necessary precision from a single trajectory data, but at expense of a progressively higher experimental resolution. Convergence is fastest around H ? 0.30, a value in the subdiffusive regime.

Advanced Control for Very Fast DC-DC Converters Based on Hysteresis of the C-out Current

The bandwidth achievable by using voltage mode control or current mode control in switch-mode power supply is limited by the switching frequency. Fast transient response requires high switching frequency, although lower switching frequencies could be more suitable for higher efficiency. This paper proposes the use of hysteretic control of the output capacitor $(C_{out})$ current to improve the dynamic response of the buck converter. An external voltage loop is required to accurately regulate the output voltage. The design of the hysteretic loop and the voltage loop are presented. Besides, it is presented a non-invasive current sensor that allows measuring the current in the capacitor. This strategy has been applied for DVS (dynamic voltage scaling) on a 5 MHz buck converter. Experimental results validate the proposed control technique and show fast transient response from 1.5 V to 2.5 V in 2 $mu{rm s}$.

Integración de un amplificador de RF de alto rendimiento con un amplificador de envolvente con red de cancelación de rizado mediante la técnica de EER

En este artículo se presenta la integración de un amplificador de envolvente de una etapa con un amplificador de clase E mediante la técnica de Kahn o Eliminación y restauración de envolvente (EER). Esta técnica se basa en la combinación de un amplificador de potencia conmutado de alto rendimiento alimentado por una fuente de alimentación modulada. El amplificador de envolvente se ha implementado con un convertidor reductor síncrono con red de cancelación de rizado, lo cual permite reducir la relación entre la frecuencia de conmutación y el ancho de banda de gran señal del amplificador de envolvente, que es uno de los factores de diseño más limitantes en esta aplicación. Para la mejora de la linealidad se ha usado la técnica de predistorsión realizándose una validación experimental. El amplificador de envolvente conmuta a 4MHz y el amplificador de clase E a 100MHz. El rendimiento total obtenido para una modulación de amplitud en cuadratura (QAM) es del 68%, con un relación de potencia del canal adyacente (ACPR) de 40dB. Para una modulación por multiplexación por división de frecuencias ortogonales (OFDM), se ha obtenido un rendimiento total del 57% y un ACPR de 32dB.1

Application and modeling of GaN FET in 1MHz large signal bandwidth power supply for radio frequency power amplifier

In this paper, implementation and testing of non- commercial GaN HEMT in a simple buck converter for envelope amplifier in ET and EER transmission techn iques has been done. Comparing to the prototypes with commercially available EPC1014 and 1015 GaN HEMTs, experimentally demonstrated power supply provided better thermal management and increased the switching frequency up to 25MHz. 64QAM signal with 1MHz of large signal bandw idth and 10.5dB of Peak to Average Power Ratio was gener ated, using the switching frequency of 20MHz. The obtaine defficiency was 38% including the driving circuit an d the total losses breakdown showed that switching power losses in the HEMT are the dominant ones. In addition to this, some basic physical modeling has been done, in order to provide an insight on the correlation between the electrical characteristics of the GaN HEMT and physical design parameters. This is the first step in the optimization of the HEMT design for this particular application.

Transformer-coupled converter for voltage modulation techniques

In high performance digital systems as well as in RF systems, voltage scaling and modulation techniques have been adopted to achieve a more efficient processing of the energy. The implementation of such techniques relies on a power supply that is capable of rapidly adjusting the system supply voltage. In this paper, a pulsewidth modulation multiphase topology with magnetic coupling is proposed for its use in voltage modulation techniques. Since the magnetic coupling in this topology is done with transformers instead of coupled inductors, the energy storage is reduced and very fast voltage changes are achieved. Advantages and drawbacks of this topology have been previously presented in the literature and in this paper, the design criteria for implementing a power supply for the envelope elimination and restoration technique in an RF system are presented along with an implementation of the power supply.

Comparison of Boost-Based MPPT Topologies for Space Applications

Several boost-derived topologies are analyzed and compared for an aerospace application that uses a 100 V voltage bus. All these topologies have been designed and optimized considering the electrical requirements and the reduced number of space-qualified components. The comparison evaluates the power losses, mass, and dynamic response. Special attention has been paid to those topologies that may cancel the inherent right half plane zero (RHP) zero of the boost topology. Experimental results of the less common topologies are presented.

3-Phase Rectifier System with very demanding dynamic load: Architecture analysis and control strategy

A distributed power architecture for aerospace application with very restrictive specifications is analyzed. Parameters as volume, weight and losses are analyzed for the considered power architectures. In order to protect the 3 phase generator against high load steps, an intermediate bus (based in a high capacitance) to provide energy to the loads during the high load steps is included. Prototypes of the selected architecture for the rectifier and EMI filter are built and the energy control is validated.

UAS See-and-Avoid Strategy using a Fuzzy Logic Controller Optimized by Cross-Entropy in Scaling Factors and Membership Functions

This work aims to develop a novel Cross-Entropy (CE) optimization-based fuzzy controller for Unmanned Aerial Monocular Vision-IMU System (UAMVIS) to solve the seeand- avoid problem using its accurate autonomous localization information. The function of this fuzzy controller is regulating the heading of this system to avoid the obstacle, e.g. wall. In the Matlab Simulink-based training stages, the Scaling Factor (SF) is adjusted according to the specified task firstly, and then the Membership Function (MF) is tuned based on the optimized Scaling Factor to further improve the collison avoidance performance. After obtained the optimal SF and MF, 64% of rules has been reduced (from 125 rules to 45 rules), and a large number of real flight tests with a quadcopter have been done. The experimental results show that this approach precisely navigates the system to avoid the obstacle. To our best knowledge, this is the first work to present the optimized fuzzy controller for UAMVIS using Cross-Entropy method in Scaling Factors and Membership Functions optimization.

OMNIWORKS: Omnidirectional vision for human-UAV co-working

The OMNIWORKS project objective is to develop an autonomous and modular aerial inspection system for an off-shore meteorological mast up to 90m in length. The UAV was equipped with an omni-directional camera and vertical take-off/landing capabilities that should be simple enough to operate as to not need the interventions of a professional pilot under challenging situations. Therefore the tests included different aspects used to evaluate both the technical performance of the UAV behavior as well as the operators? point of view.

Autonomous Landing of an Unmanned Aerial Vehicle using Image-Based Fuzzy Control

This paper presents a vision based autonomous landing control approach for unmanned aerial vehicles (UAV). The 3D position of an unmanned helicopter is estimated based on the homographies estimated of a known landmark. The translation and altitude estimation of the helicopter against the helipad position are the only information that is used to control the longitudinal, lateral and descend speeds of the vehicle. The control system approach consists in three Fuzzy controllers to manage the speeds of each 3D axis of the aircraft s coordinate system. The 3D position estimation was proven rst, comparing it with the GPS + IMU data with very good results. The robust of the vision algorithm against occlusions was also tested. The excellent behavior of the Fuzzy control approach using the 3D position estimation based in homographies was proved in an outdoors test using a real unmanned helicopter.

Interleaved multi-cell isolated three-phase PWM rectifier system for aircraft applications

Recently there has been an important increase in electric equipment, as well as, electric power demand in aircrafts applications. This prompts to the necessity of efficient, reliable, and low-weight converters, especially rectifiers from 115VAC to 270VDC because these voltages are used in power distribution. In order to obtain a high efficiency, in aircraft application where the derating in semiconductors is high, normally several semiconductors are used in parallel to decrease the conduction losses. However, this is in conflict with high reliability. To match both goals of high efficiency and reliability, this work proposes an interleaved multi-cell rectifier system, employing several converter cells in parallel instead of parallel-connected semiconductors. In this work a 10kW multi-cell isolated rectifier system has been designed where each cell is composed of a buck type rectifier and a full bridge DC-DC converter. The implemented system exhibits 91% of efficiency, high power density (10kW/10kg), low THD (2.5%), and n−1 fault tolerance which complies, with military aircraft standards.

Limits of the frequency response for the analysis of ripple-based controllers

Advanced control techniques like V2, Vout hysteresis or V2Ic can strongly reduce the required output capacitance in PowerSoC converters. Techniques to analyze power converters based on the analysis of the frequency response are not suitable for ripple-based controllers that use fast-scale dynamics to control the power stage. This paper proves that the use of discrete modeling together with Floquet theory is a very powerful tool to model the system and derive stable region diagrams for sensitivity analysis. It is applied to V 2Ic control, validating experimentally that Floquet theory predicts accurately subharmonic oscillations. This method is applied to several ripplebased controllers, providing higher accuracy when it is compared with other techniques based on the frequency response. The paper experimentally validates the usefulness of the discrete modeling and the Floquet theory on a 5 MHz Buck converter with a V 2Ic control.

Improvement of the Dynamic Performance of a Multiphase Current Controlled Buck Converter using an Auxiliary Synchronous Buck Converter as an Additional Energy Path

This work is related to the output impedance improvement of a Multiphase Buck converter with Peak Current Mode Control (PCMC) by means of introducing an additional power path that virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a Single Phase Buck converter with Voltage Mode Control (VMC), while in the VRM applications, due to the high currents, the system is usually implemented as a Multiphase Buck Converter with Current Mode Control. The additional energy path, as presented here, is introduced with the Output Impedance Correction Circuit (OICC) based on the Controlled Current Source (CCS). The OICC is used to inject or extract a current n-1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, this work extends the OICC concept to a Multiphase Buck Converter system while comparing proposed solution with the system that has n times bigger output capacitor. In addition, the OICC is implemented as a Synchronous Buck Converter with PCMC, thus reducing its influence on the system efficiency.

Forward micro-inverter with primary-parallel secondary-series multicore transformer

This paper presents a primary-parallel secondary-series multicore forward micro-inverter for photovoltaic AC-module application. The proposed solution changes the number of active phases depending on the grid voltage, thus enabling the usage of low-profile unitary turns ratio transformers. Therefore, the transformers are well coupled and the overall performance of the inverter is improved. Due to the multiphase solution the number of devices increases but, the current stress and losses per device are reduced contributing to an easier thermal management. Furthermore, the decoupling capacitor is split between the phases, contributing to a low-profile solution without electrolytic capacitors suitable to be mounted in the frame of a PV module.