BRAIN COMPUTER INTERFACE - Application of an Adaptive Bi-stage Classifier based on RBF-HMM

Brain Computer Interface is an emerging technology that allows new output paths to communicate the users intentions without the use of normal output paths, such as muscles or nerves. In order to obtain their objective, BCI devices make use of classifiers which translate inputs from the users brain signals into commands for external devices. This paper describes an adaptive bi-stage classifier. The first stage is based on Radial Basis Function neural networks, which provides sequences of pre-assignations to the second stage, that it is based on three different Hidden Markov Models, each one trained with pre-assignation sequences from the cognitive activities between classifying. The segment of EEG signal is assigned to the HMMwith the highest probability of generating the pre-assignation sequence. The algorithm is tested with real samples of electroencephalografic signal, from five healthy volunteers using the cross-validation method. The results allow to conclude that it is possible to implement this algorithm in an on-line BCI device. The results also shown the huge dependency of the percentage of the correct classification from the user and the setup parameters of the classifier

Application of sources reconstruction techniques: Theory and practical results.

In this paper, four new applications of sources reconstruction techniques (also called diagnostic techniques) are presented. First of all, the important information of such techniques will be mentioned, seeing that they are a tool to obtain the extremely near field from the measured data. Depending on the region where these data are taken (near field or far field), the reconstruction method will be different. Also, all of them may be classified in other two groups depending on its features: Integral Equation Methods (IEM) or Modal Expansion Methods. Classical applications of such techniques are errors detection, like phase errors in arrays or conformai errors in reflectors, therefore, they constitute an important antenna design tool. But also and it has been said, they can be used as the basis to other applications whose aim is to improve the measurement results in anechoic chambers or non anechoic environments. Here, four of them are presented, being the reflection cancelling, the detection of unwanted radiation points, the truncation error reduction in planar or cylindrical near-field and the noise reduction

A spreading method to improve efficiency prediction.

In efficiency analysis by means of a stochastic frontier production function, the composite error variable includes the inefficiency component. For this reason, individual prediction cannot be made directly from an estimation of the error in the model. In order to solve this problem, Jondrow et al (1982), and Battese and Coelli (1988) separately developed two different procedures, based on the expectation operator of the conditional distributions. Although the two predictors are different, each suffers from a shrinkage effect with respect to the distribution of theoretical efficiency. Our study of the behaviour of these two predictors leads us to conclude that the value of the gamma parameter has a great influence on the above-mentioned effect, producing a truncation of the distribution that could be more than 50%, so that the extreme values of the efficiency can never be estimated by the predictors considered. We also propose a method that spreads out the predicted efficiencies in order to minimise the shrinkage effect. The Monte Carlo results demonstrate that the corrected predictions have a better behaviour than the original predictors.Efficiency, Frontier models, Monte Carlo methods.

Debiasing EQ-5D Tariffs. New estimations of the spanish EQ-5D value set under nonexpected utility

Este proyecto tiene como objetivo estimar las utilidades asociadas a los estados de salud definidos mediante el sistema EuroQol-5D a partir de la medición directa de las preferencias de una muestra de la población andaluza. Los valores obtenidos serán susceptibles de ser utilizados en el marco de estudios de evaluación económica de políticas sanitarias (análisis coste-utilidad) realizados en la comunidad andaluza y en el conjunto del estado. Para la valoración directa de un subconjunto de estados de salud se realizará una encuesta personal asistida por ordenador a una muestra representativa por sexo y cuotas de edad de la población española, extraída de la población residente en Andalucía. Los métodos que se aplicarán para obtener las preferencias y calcular las utilidades tratarán de corregir algunos de los sesgos que pueden afectar a las estimaciones existentes. Así, se adoptarán enfoques teóricos alternativos a los habitualmente empleados que permitirán relajar algunos de los supuestos que han sido puestos en cuestión a la luz de la evidencia empírica, como es el caso de la linealidad de la función de utilidad del tiempo de vida, la validez descriptiva de la teoría de la utilidad esperada o la separabilidad multiplicativa de las preferencias por cantidad y calidad de vida.EQ-5D, social tariff, utility curvature, probability weighting, rank-dependent utility, time trade-off, value lottery equivalence, certainlty equivalence

Contrastación empírica del efecto Fisher en 11 países de la UE

[Resumen]: Este trabajo analiza el cumplimiento del efecto Fisher en los once países que en 1999 adoptaron como moneda única el euro utilizando una metodología de series de tiempo basada en técnicas de cointegración con datos mensuales de la inflación y swaps a 2, 5 y 10 años en el periodo comprendido entre marzo de 2005 y agosto de 2017. Adicionalmente se verifica la velocidad de ajuste entre las variables utilizadas y si se cumple la relación de uno a uno entre ambas series. Los resultados empíricos obtenidos muestran que se cumple el efecto Fisher en su forma débil para todos los países analizados y en su versión fuerte solo para Alemania, Francia, Holanda e Italia. Este cumplimiento asimétrico del efecto Fisher implica que el tipo de interés real no permanece constante en algunos de los países analizados y, por ello, la política monetaria del Banco Central se trasmite de forma asimétrica, pudiendo estimular o enfriar la economía de aquellos países en los que el tipo de interés real no permanece constante.[Abstract]: This paper analyses Fisher effect in the eleven countries that in 1999 adopted the euro as a single currency using time series analysis based on cointegration tests over monthly inflation data and 2, 5 and 10 years swaps for the period between March 2015 and August 2017. Additionally, speed of adjustments between variables in use is verified and also if 1:1 relation for the series is met. Empiric results achieved indicate the presence of the weak form of Fisher effect for all countries analysed but only strong form for Germany, France, Netherlands and Italy. This asymmetric Fisher effect achievement implies inconstant actual interest rate for some of the countries studied and, hence, the monetary policy of the Central Bank is asymmetrically transmitted, stimulating or cooling down economy of those countries where the actual interest rate do not remain constant.Traballo fin de mestrado (UDC.ECO). Banca e finanzas. Curso 2016/201

New methods to reduce leakage errors in planar near-field measurements

This paper describes two methods to cancel the effect of two kinds of leakage signals which may be presented when an antenna is measured in a planar near-field range. One method tries to reduce leakage bias errors from the receiver¿s quadrature detector and it is based on estimating the bias constant added to every near-field data sample. Then, that constant is subtracted from the data, removing its undesired effect on the far-field pattern. The estimation is performed by back-propagating the field from the scan plane to the antenna under test plane (AUT) and averaging all the data located outside the AUT aperture. The second method is able to cancel the effect of the leakage from faulty transmission lines, connectors or rotary joints. The basis of this method is also a reconstruction process to determine the field distribution on the AUT plane. Once this distribution is known, a spatial filtering is applied to cancel the contribution due to those faulty elements. After that, a near-field-to-far-field transformation is applied, obtaining a new radiation pattern where the leakage effects have disappeared. To verify the effectiveness of both methods, several examples are presented