Search results for "Variable"

Faults diagnosis based on proportional integral observer for TS fuzzy model with unmeasurable premise variable

2014

In this work, we focus on the synthesis of a Proportional Integral (PI) observer for the actuators and sensors faults diagnosis based on Takagi-Sugeno (TS) fuzzy model with unmeasurable premise variables. The faults estimation method is based on the assumption that these faults act as unknown inputs under polynomials form whose their kth derivatives are bounded. The convergence conditions of the observer as well as the faults reconstruction are established on the basis of the Lyapunov stability theory and the L 2 optimization technique, expressed as Linear Matrix Inequalities (LMI) constraints. In order to validate the proposed approach, a hydraulic system with two tanks is proposed.

Dynamic Output-Feedback Passivity Control for Fuzzy Systems under Variable Sampling

2013

Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/767093 Open Access This paper concerns the problem of dynamic output-feedback control for a class of nonlinear systems with nonuniform uncertain sampling via Takagi-Sugeno (T-S) fuzzy control approach. The sampling is not required to be periodic, and the state variables are not required to be measurable. A new type fuzzy dynamic output-feedback sampled-data controller is constructed, and a novel time-dependent Lyapunov-Krasovskii functional is chosen for fuzzy systems under variable sampling. By using Lyapunov stability theory, a sufficie…

Variable length Markov chains and dynamical sources

2010

Infinite random sequences of letters can be viewed as stochastic chains or as strings produced by a source, in the sense of information theory. The relationship between Variable Length Markov Chains (VLMC) and probabilistic dynamical sources is studied. We establish a probabilistic frame for context trees and VLMC and we prove that any VLMC is a dynamical source for which we explicitly build the mapping. On two examples, the ``comb'' and the ``bamboo blossom'', we find a necessary and sufficient condition for the existence and the unicity of a stationary probability measure for the VLMC. These two examples are detailed in order to provide the associated Dirichlet series as well as the gener…

Country size and business cycle volatility: Scale really matters

2007

Abstract In a recent study Andrew Rose found that country size does not matter for several economic outcomes [Rose, A.K., 2006. Size really doesn't matter: In search of a national scale effect. J. Japanese Int. Economies 4, 482–507]. However, he did not consider the effect that country size may have on business-cycle volatility. To investigate the empirical relationship between business cycle volatility and country size, we use a panel data set that includes 167 countries from 1960 to 2000. The results suggest very strongly that the relationship between country size and business cycle volatility is negative and statistically significant. This implies that smaller countries are subject to mo…

Estimating the gravity equation with the actual number of exporting firms

2013

Para estimar correctamente el efecto de los costes de comerciar sobre las exportaciones de las empresas, la ecuación de gravedad debe controlar por el número de empresas que opera en el mercado internacional. Debido a la ausencia de datos, estudios anteriores han controlado esta variable mediante técnicas econométricas que también pueden generar estimaciones sesgadas. Para superar estos problemas este trabajo estima una ecuación de gravedad utilizando una nueva base de datos de la OCDE y EUROSTAT , que incluye el número de empresas exportadoras en cada relación bilateral. Nuestros resultados muestran que no controlar el margen extensivo genera sesgos muy importantes en la estimación de los …

Improved Predictability for Foreign Direct Investors by Comprising Different Macroeconomic Levels: A New Model Approach

2020

Foreign direct investments have grown over the last decades which are related to the ongoing globalization process. The current literature shows research works dealing with the topic of influence factors on foreign direct investment (FDI) decisions which may occur during the decision-making process. A new causal model has been developed to get in-depth view on macroeconomic perspective. Motives to do FDI are strongly impacted by macroeconomic factors which may influence upcoming decisions. To be able to understand the impact of the macroeconomic environment on FDI decisions the factors have been diversified and conceptualized, divided into three subgroups of independent latent variables in …

Product and process innovation and total factor productivity: Evidence for manufacturing in four Latin American countries

2017

The literature on firm productivity recognizes the important role played by firm innovation activities on firm productivity in developed countries. However, the literature for developing and emerging economies is scarce and far from conclusive. The aim of this paper is to study the innovation–productivity link (distinguishing between process and product innovations) for manufacturing at the firm level for four Latin American countries (two classified as upper-middle income countries by the World Bank—Argentina and Mexico—and two as lower-middle income—Colombia and Peru). We aim testing whether the level of development is a mediating factor in the innovation–productivity link. The data used …

The financial impact of Spanish pension reform: A quick estimate

2012

In this paper, we present a preliminary estimate of the financial impact of the recent reform of the Spanish pension system. After updating the projections of pension expenditure constructed in de la Fuente and Doménech (2010) for the period 2008-2060, we analyze the impact on this variable of raising the retirement age from 65 to 67 years, extending from 15 to 25 years the period over which wages are averaged to calculate the starting pension and increasing from 35 to 37 the number of contribution years required to obtain a 'full pension.' Conditional on a series of assumptions about the evolution of employment, productivity and demographics, our estimates suggest that these measures will …

Accretion disk coronae of intermediate polar cataclysmic variables

2017

Context. Intermediate polar cataclysmic variables (IPCV) contain a magnetic, rotating white dwarf surrounded by a magnetically truncated accretion disk. To explain their strong flickering X-ray emission, accretion has been successfully taken into account. Nevertheless, observations suggest that accretion phenomena might not be the only process behind it. An intense flaring activity occurring on the surface of the disk may generate a corona, contribute to the thermal X-ray emission, and influence the system stability. Aims. Our purposes are: investigating the formation of an extended corona above the accretion disk, due to an intense flaring activity occurring on the disk surface; studying t…

Accretion disk coronae of Intermediate Polar Cataclysmic Variables: 3D MagnetoHydroDynamic modeling and thermal X-ray emission

Intermediate Polar Cataclysmic Variables (IPCVs), also known as DQ Her stars after their prototype, are cataclysmic variable stars characterized by the presence of an accreting, magnetic, rapidly rotating white dwarf surrounded by an accretion disk magnetically truncated by the inner magnetosphere of the star. These objects exhibit a magnetic field of the order of few MG, able to disrupt the inner part of the disk but not strong enough to inhibit the formation of a disk. These stars show a strong X-ray emission with a stochastic pulsation that in some cases arise in the inner part of the disk. However, the observations of the X-ray luminosity for these objects do not match the expected valu…