Neural Network Local Navigation of Mobile Robots in a Moving Obstacles Environment

IF AC Intelligent Components and Instruments for Control Applications, Budapest, Hungary, 1994This paper presents a local navigation method based on generalized predictive control. A modified cost function to avoid moving and static obstacles is presented. An Extended Kaiman Filter is proposed to predict the motions of the obstacles. A Neural Network implementation of this method is analysed. Simulation results are shown.Ministerio de Ciencia y Tecnología TAP93-0408Ministerio de Ciencia y Tecnología TAP93-058

The impact of immigration on the wage structure : Spain 1995-2002

In this paper we estimate the impact of inward migration flows on the Spanish wage structure over the period 1995-2002 by constructing counterfactual wage distributions that provide the wages that would have been observed had individual and job characteristics remain constant over time. Hence, we compute the impact of immigration on the wage distribution from (i) the estimated wage gaps between similar immigrants and native workers and (ii) the changes in the composition of employment associated to the arrival of new immigrants. Overall, we find that (i) the effects of immigration on wage changes are small and only noticeable when job characteristics are included as determinants of wages, and (ii) the correlation between the incidence of immigration in each decile of the wage distribution and the change in native wages not explained by changes in their individual and job characteristics is positive. These results suggest that other factors, besides immigration, should be identified as the key determinants of the wage moderation observed since the early nineties in Spain

The effect of immigration on the employment opportunities of native-born workers : some evidence for Spain

Spain is one of the European countries where immigration flows during the last decade have increased noticeably. The Spanish labor market institutions and the Spanish immigration policy exhibit some peculiarities which may be relevant when analyzing the impact of immigration. This paper provides a first approximation to the labor market effects of immigrants in Spain during the second half of the 1990s, the period in which immigration flows to Spain have accelerated. By using alternative datasets, we estimate both the impact of legal and total immigration flows on the employment rates of native workers, accounting for the possible occupationa l and geographical mobility of immigrants and native-born workers. Using different samples and estimation procedures, we have not found a significant negative effect of immigration on the employment rates of native workers. The corresponding estimated elasticity is low, around -0.1, when considering only legal immigrants, and is not significant when considering both legal and illegal immigrants

Fuzzy Predictive Controller for Mobile Robot Path Tracking

IFAC Intelligent Components and Instruments for Control Applications, Annecy, France 1997This paper presents a way of implementing a Model Based Predictive Controller (MBPC) for mobile robot path-tracking. The method uses a non-linear model of mobile robot dynamics and thus allows an accurate prediction of the future trajectories. Constraints on the maximum attainable angular velocity is also considered by the algorithm. A fuzzy approach is used to implement the MBPC. The fuzzy controller has been trained using a lookup-table scheme, where the database of fuzzy-rules has been obtained automatically from a set of input-output training patterns, computed with the predictive controller. Experimental results obtained when applying the fuzzy controller to a TRC labmate mobile platform are given in the paper.Ministerio de Ciencia y Tecnología TAP95-0307Ministerio de Ciencia y Tecnología TAP96-884C

The impact of immigration on the wage structure : Spain 1995-2002

In this paper we estimate the impact of inward migration flows on the Spanish wage structure over the period 1995-2002 by constructing counterfactual wage distributions that provide the wages that would have been observed had individual and job characteristics remain constant over time. Hence, we compute the impact of immigration on the wage distribution from (i) the estimated wage gaps between similar immigrants and native workers and (ii) the changes in the composition of employment associated to the arrival of new immigrants. Overall, we find that (i) the effects of immigration on wage changes are small and only noticeable when job characteristics are included as determinants of wages, and (ii) the correlation between the incidence of immigration in each decile of the wage distribution and the change in native wages not explained by changes in their individual and job characteristics is positive. These results suggest that other factors, besides immigration, should be identified as the key determinants of the wage moderation observed since the early nineties in Spain.Immigration, Wage structure, Quantile regressions

Application of a Natural Language Interface to the Teleoperation of a Mobile Robot

IFAC Intelligent Components for Vehicles, Seville, Spain, 1998This paper describes the application of a natural language interface to the teleoperation of a mobile robot. Natural language communication with robots is a major goal, since it allows for non expert people to communicate with robots in his or her own language. This communication has to be flexible enough to allow the user to control the robot with a minimum knowledge about its details. In order to do this, the user must be able to perform simple operations as well as high level tasks which involve multiple elements of the system. For this ones, an adequate representation of the knowledge about the robot and its environment will allow the creation of a plan of simple actions whose execution will result in the accomplishment of the requested tas

Robust PID tuning. Application to a Mobile Robot Pathtraking problem.

IFAC Digital Control: Past,Present and Future of PlO Control.Terrassa.Spain.2000This paper presents a methodology for tuning PIDs considering the nominal performance and the robustness as control specifications. The synthesis procedure is similar to the Ziegler-Nichols method for PID controllers and can be easily used for industrial processes. As a workbench for testing the PID controller a mobile robot has been used. The path tracking problem of a mobile robot has been used as a workbench for testing the PID controller

Declining returns to skill and the distribution of wages : Spain 1995-2006

In contrast to the pattern observed in other developed countries, Spanish wage inequality did not increase during the period from 1995-2006. In this paper we analyse the relative role of supply and demand factors when accounting for this “atypical” fact. Because noticeable changes in both labour supply and labour demand - such as educational upgrading of the labour force, huge immigration flows, and a boom in the construction sector - took place during these years, we start by decomposing observed wage changes into changes in the composition of the labour force and changes in the prices of workers’ and jobs’ characteristics. The results indicate that the compression of the wage distribution is largely explained by a decrease in the returns to education. We also provide some evidence of the relative impact of labour supply and labour demand factors on the changes of these returns, showing that both the increase in the supply of high-skilled workers and the increasing weight of low-skilled occupations are related to the decreasing trend in the skill premium over this period.The first author aknowledges research funding from the Spanish Ministry of Science and Innovation, Grant No. ECO2009-1116

Accounting for changes in the Spanish wage distribution : the role of employment composition

A pesar de una rápida disminución del desempleo, los salarios reales en España apenas aumentaron durante el periodo 1995-2006. Una posible explicación de este comportamiento se refiere a la importancia de los efectos composición derivados de algunos cambios estructurales, tales como el aumento del peso del empleo en la construcción y en el sector servicios, el incremento de la participación laboral femenina, y la llegada masiva de inmigrantes. Utilizando datos de tres olas de la Encuesta de Estructura Salarial, se descompone la variación salarial observada durante este periodo en dos componentes, el debido a los cambios en las características de los puestos de trabajo y de los trabajadores, y el causado por los cambios en los rendimientos de dichas características. Así, mediante regresiones cuantílicas que estiman ecuaciones de salarios condicionadas a determinados percentiles de la distribución salarial, se construyen las istribuciones contrafactuales que se hubieran observado de haberse mantenido constantes las características de los puestos de trabajo y de los trabajadores. El principal resultado es que la falta de crecimiento de los salarios reales en España durante el periodo 1995-2006 se debe, sobre todo, a la caída de los rendimientos, especialmente de la educación y de la experiencia laboral en los deciles elevados de la distribución salarial, y no tanto a cambios en la composición del empleo que, computados sobre un conjunto amplio de características, tuvieron un efecto global positivo sobre los salario

Analysis of the image of immigration in prime time television fiction

This article presents the results of a research study into the image of immigration as presented in television fiction, taking Cultivation Theory as a reference. Content analysis was performed on a representative sample of prime-time fictional programming broadcast in 2010 on six television channels. Results show that immigrant characters are under-represented and their construction is based on negative stereotypes. These results are discussed in relation to the role of television fiction in reducing prejudice