One dimensional description of the gravitational perturbation in a Kerr background

The perturbation equation in a Kerr background is written as a coupled system of one dimensional equations for the different modes in the time domain. Numerical simulations show that the dominant mode in the gravitational response is the one corresponding to the mode of the initial perturbation, allowing us to conjecture that the coupling among the modes has a weak influence in our system of equations. We conclude that by neglecting the coupling terms it can be obtained a one dimensional harmonic equation which indeed describes with good accuracy the gravitational response from the Kerr black hole with low spin, while only few couplings are necessary to describe a high spin one. This result may help to understand the structure of test fields in a Kerr background and even to generate accurate waveforms for various cases in an efficient manner.Comment: 14 pages, 3 figure

The Impact of Public and Private Job Training in Colombia

The authors present matching estimators of the impact on earnings for individuals who attended public and private job training programs in Colombia. They estimate propensity scores by controlling for the variety of personal and socioeconomic background variables of those individuals. The effect of training, measured by the mean impact of the treatment on the treated, shows that: (i) for youths, no institution has a significant impact in the short or long run except private institutions for males; the scope of the data, however, limits the reliability of the result; (ii) for adult males, neither SENA nor the other public institutions have a significant impact in the short or long run; (iii) for SENA-trained adult females there are positive but not significant impacts in the short run and greater and close to significant effects in the long run. All other public institutions have a higher impact that is significant in the long-run; (iv) for adults trained at private institutions there are large and significant effects in both the short and long run, but for adult males in the short run the effects are smaller and only barely significant. In addition, neither short nor long courses provided by SENA seem to have a significant impact on earnings. In general, females benefit more from both short and long courses than males. Finally, a cost-benefit analysis shows that under the assumption of direct unitary costs equal to SENA, private institutions are more profitable than public institutions, which are in turn more profitable than SENA.

Predictive control of a solar air conditioning plant with simultaneous identification

This paper presents the application of a predictive controller with simultaneous identification to a solar air conditioning plant. The time varying nature of the process makes necessary an adjustment of the controller parameters to the varying operational conditions. The main novelty with respect to classic adaptive MPC scheme is to penalize the identification error in the cost function used for control. The behaviour of the controller is illustrated by simulations and experimental results. The integration of identification and control avoids the tedious identification procedure that is necessary before the start-up of any predictive controller. This new adaptive MPC scheme shows its effectiveness in controlling the outlet temperature in the solar thermal plant.Ministerio de Ciencia y Tecnología DPI2004-07444-C04-0

The impact of real estate projects and their sustainability characteristics on land values: cause or consequence? two case studies from Santiago, Chile

From the point of view of developers, there is the belief that location determines the main characteristics of real estate projects. On the contrary, the bid rent theory proposes that land receives value from that which it supports, as expressed by means of architectural attributes. In light of two case studies in Santiago, Chile, the relationship between land value and real estate value was studied with the aim of identifying the meaning of this causality and the role of sustainability characteristics – as an expression of emergent architectural attributes – in price formation. It was observed that the interaction between land value and architectural characteristics generates property price through circular causality, where there is a certain typology for each location that can produce submarkets. In this sense, sustainability attributes effectively influence the creation of value – but not linearly – which clearly suggests the presence of housing submarkets according to price level, and a new element in the relationship between land and architectural attributes.Postprint (published version

Peer Victimization in Overweight Adolescents and Its Effect on Their Self-Esteem and Peer Difficulties

This study has three objectives: to examine whether adolescents who perceive themselves as overweight differ from others in terms of offline victimization at school, cybervictimization, self-esteem, and difficulties relating to peers; to examine the possible effects of offline and cybervictimization on self-esteem and difficulties relating to peers; and to examine the possible moderating role of perceiving oneself as overweight on those effects. Previously validated questionnaires were applied to a sample of 3145 adolescents in Asturias (Spain). Descriptive, inferential, correlational, and structural equation analyses were performed. Adolescents who perceived themselves as overweight reported being victims of both offline victimization and most forms of cybervictimization to a greater extent than those who did not perceive themselves as overweight. They also reported lower self-esteem and more peer difficulties (shyness or social anxiety). In both groups of adolescents, victimization and cybervictimization were correlated with each other, both types of victimization had direct, negative effects on self-esteem, and self-esteem in turn had a direct, negative effect on peer difficulties. Furthermore, offline victimization had a direct, positive effect on peer difficulties. Perceiving oneself as overweight moderated the effect of self-esteem on peer difficulties. In adolescents perceiving themselves as overweight, low self-esteem was a stronger risk factor of peer difficulties than in the rest of the adolescents. With high overall self-esteem there were no significant differences in peer difficulties between the adolescents perceiving themselves as overweight and the rest of the adolescents

Differentials and persistence in unemployment - an analysis of the Spanish regions with the highest unemployment rates

The objective of the present paper is to contribute to the study of the labour markets of two Spanish regions that have mantained over the last few decades a persistent unemployment differential with respect to the remainder of the country: Andalusia and Extremadura. To this end, a brief descriptive analysis is given of the most important variables of these regional labour makets, together with the corresponding shift-share and virtual economy analysis. To study the degree of persistence of the unemployment rate in these two regions, the behaviour of their labour markets in response to specific shocks in employment is examined by means of a VAR analysis, following the method proposed by Blanchard y Katz (1992). One of the most noteworthy aspects brought out by the descriptive analysis was that, although the labour markets of Andalusia and Extremadura share many characteristics - indeed most of those that were analyzed- they also present differenciated patterns of behaviour in some important variables. For example, in the case of Andalusia economy, there is a notably strong growth of the labor force. This contrasts whit the weakness of employment growth in the Extremadura economy. Also worthy of note is the greater wage flexibility in Extremadura compared to Andalusia. From the VAR analysis applied to each of these two regions, one can conclude that a specific demand shock in Andalusia and Extremadura has permanent effects on the participation rate - especially in Andalusia- and on the unemployment rate - especially in Extremadura-, with the migratory movements in these regions being too low to return these variables to the level they had prior to the demand shock. In sum, the present paper points to a set of factors that could contribute to explaining the unemployment differentials of Andalusia and Extremadura relative to the rest of Spain. More specific analyses would be required to evaluate the explanatory capacity of each of these factors in accordance with the underlying methodology and theories corresponding to each case.

Some discrete approaches to continuum economies

Given the preferences of the agents of a continuum economy, we define the average and unanimous preference. This allow us to consider several sequences of economies, in which only a finite number of different agents' characteristics can be distinguished. We obtain approximation results for the core of these economies

The Mexican intertemporal budget constraint: Persistent signals of an eventual collapse

This paper examines the sustainability of the Mexican current account deficit prior to the December 1994 crisis. It tests whether or not the Mexican economy was satisfying its intertemporal budget constraint, and finds that signals of possible trouble without a change in policies were present long before the crisis. The tests used are based on the Wickens-Uctum criterion for the sustainability of current account deficits, extended to include the case of possible interventions.intertemporal budget constraint, current account, sustainability of current account deficit, Mexico

Predictive control of an olive oil mill with multi-objective prioritization

INTERNATIONAL FEDERATION OF AUTOMATIC CONTROL. WORLD CONGRESS (15.2002.BARCELONA)This paper presents a multi-objective controller applied to an olive oil mill. The practical experience using a Generalized Predictive Controller (GPC) in the real plant showed the necessity of including objectives, with different priorities, in the process control. The analysis demonstrates that GPC with prioritization objectives can control the process and fulfill the specified operational conditions. The results are illustrated with some simulations that compare the traditional GPC to the multi-objective one.Comisión Europea 1FD97-0836 (FEDER