Numerical issues in threshold autoregressive modelling of time series

This paper analyses the contribution of various numerical approaches to making the estimation of threshold autoregressive time series more efficient. It relies on the computational advantages of QR factorizations and proposes Givens transformations to update these factors for sequential LS problems. By showing that the residual sum of squares is a continuous rational function over threshold intervals it develops a new fitting method based on rational interpolation and the standard necessary optimality condition. Taking as benchmark a simple grid search, the paper illustrates via Monte Carlo simulations the efficiency gains of the proposed tools

How secular staganation can affect income class structure in european countries: institutional and policy implications

In recent years, there has been increasing debate about the low economic growth and the risk of secular stagnation in economically advanced countries. Some authors point out possible links between secular stagnation and income inequality, causally in both directions. Taking as a reference point the theoretical literature on the relationship between economic growth and income distribution, this study examines the extent to which different levels of economic growth are associated with the income class structure in European countries between 1993 and 2016, focusing on income distribution before taxes and transfers (market incomes). We highlight that in recession periods the size and income share of the middle class decrease, while the opposite occurs in periods with strong economic growth rates. Nevertheless, when growth rates are modest the patterns are much less clearly defined. Some policy and institutional implications are discussed in order to tackle the concerns of secular stagnation and inequality simultaneously.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Auditoria Administrativa : Auditoria Operacional en las Organizaciones

En nuestra actualidad las organizaciones están trabajando cada vez en supervisar y evaluar de forma independiente todas las operaciones de una empresa, todo esto se realiza con el objetivo de determinar si se siguen las normas establecidas; si utilizan los recursos de forma eficaz y económica; y si los objetivos de la organización se han alcanzado para así maximizar resultados que fortalezcan el desarrollo de la empresa. En el presente trabajo destacamos la relevancia de realizar periódicamente auditorías operacionales en la administración de las organizaciones, el cual nos conlleva a una serie de aspectos que se deben tomar en cuenta: las generalidades de la auditoría operacional, el rol y las funciones de los auditores dentro de las empresas, normas y herramientas para llevar a cabo una auditoría operacional. Debido a la gran importancia que tiene la auditoría operacional en las empresas, se procede a analizar y enumerar las normas, técnicas y herramientas usadas para determinar cómo han sido empleados los recursos dentro de las organizaciones de esta manera dar a conocer los problemas que dificultan el desarrollo operativo los cuales obstaculizan el crecimiento de la empresa y a la misma vez proponer soluciones adecuadas e implementarlas para obtener como resultado el alcance de los objetivos propuestos en la compañía. Dicho trabajo estuvo enmarcado en un tipo de investigación documental, en donde se emplearon una serie de técnicas e instrumentos de recolección de datos; específicamente de fuentes documentales como libros y sitios web

Neoclassical growth and the natural resource curse puzzle

We advance a novel mechanism that helps to explain the puzzling evidence on the natural resource curse. The new channel arises in a standard dynamic Heckscher-Ohlin model composed of small-open economies that take international output prices as given. Within this framework, a more capital-intensive primary sector implies that natural-resource abundant economies grow more slowly along the adjustment path. This effect might be only temporary because the natural input also affects long-run income, and not necessarily in the same direction as transitional growth. We produce quantitative results that show that the new mechanism can account for a significant fraction of the observed output growth gap between resource rich and resource poor U.S. states

A Double Classification of Common Pitfalls in Ontologies

The application of methodologies for building ontologies has improved the ontology quality. However, such a quality is not totally guaranteed because of the difficulties involved in ontology modelling. These difficulties are related to the inclusion of anomalies or worst practices in the modelling. In this context, our aim in this paper is twofold: (1) to provide a catalogue of common worst practices, which we call pitfalls, and (2) to present a double classification of such pitfalls. These two products will serve in the ontology development in two ways: (a) to avoid the appearance of pitfalls in the ontology modelling, and (b) to evaluate and correct ontologies to improve their quality

Nonlinear model predictive control for hydrogen production in an ethanol steam reformer with membrane separation

© 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper presents a new Nonlinear Model Predictive Control (NMPC) design for an Ethanol Steam Reformer with Pd-Ag membrane separation stage. The reformer is used to produce pure hydrogen able to feed a Proton Exchange Membrane Fuel Cell. Mass and energy balances are used to obtain the nonlinear dynamic model of both the reforming and the separation stages. Constraints, system nonlinearities and flexible cost function are the main reasons to select an NMPC controller, which is tested against the ordinary differential equations as simulation model, and has an internal model based on the sample data technique.Accepted versio