Trend analysis in two standard growth models

This paper analyzes the trend processes characterized by two standard growth models using simple econometrics. The first model is the basic neoclassical growth model that postulates a deterministic trend for output. The second model is the Uzawa-Lucas model that postulates a stochastic trend for output. The aim is to understand how the different trend processes for output assumed by these two standard growth models determine the ability of each model to explain the observed trend processes of other macroeconomic variables such as consumption and investment. The results show that the two models reproduce the output trend process. Moreover, the results show that the basic growth model captures properly the consumption trend process, but fails in characterizing the investment trend process. The reverse is true for the Uzawa-Lucas model.Uzawa-Lucas model, basic neoclassical growth model, trend process, cointegration

Cyclical Features of Uzawa-Lucas Endogenous Growth Model

This paper analyzes the cyclical properties of a generalized version of Uzawa-Lucas endogenous growth model. We study the dynamic features of different cyclical components of this model characterized by a variety of decomposition methods. The decomposition methods considered can be classified in two groups. On the one hand, we consider three statistical filters: the Hodrick-Prescott filter, the Baxter-King filter and Gonzalo-Granger decomposition. On the other hand, we use four model-based decomposition methods. The latter decomposition procedures share the property that the cyclical components obtained by these methods preserve the log-linear approximation of the Euler-equation restrictions imposed by the agent’s intertemporal optimization problem. The paper shows that both model dynamics and model performance substantially vary across decomposition methods. A parallel exercise is carried out with a standard real business cycle model. The results should help researchers to better understand the performance of Uzawa-Lucas model in relation to standard business cycle models under alternative definitions of the business cycle.endogenous growth, decomposition methods, cyclical features

Trend analysis in two standard growth models

This paper analyzes the trend processes characterized by two standard growth models using simple econometrics. The first model is the basic neoclassical growth model that postulates a deterministic trend for output. The second model is the Uzawa-Lucas model that postulates a stochastic trend for output. The aim is to understand how the different trend processes for output assumed by these two standard growth models determine the ability of each model to explain the observed trend processes of other macroeconomic variables such as consumption and investment. The results show that the two models reproduce the output trend process. Moreover, the results show that the basic growth model captures properly the consumption trend process, but fails in characterizing the investment trend process. The reverse is true for the Uzawa-Lucas model.Financial support from Ministerio de Ciencia y Tecnología, Gobierno Vasco and Universidad del País Vasco (Spain) through projects BEC2000-1393, PI-1999-131 and 9/UPV00035.321-13511/2001, respectively, is gratefully acknowledged

Truth Values in t-norm based Systems Many-valued FUZZY Logic

In t-norm based systems many-valued logic, valuations of propositions form a non-countable set: interval [0,1]. In addition, we are given a set E of truth values p, subject to certain conditions, the valuation v is v=V(p), V reciprocal application of E on [0,1]. The general propositional algebra of t-norm based many-valued logic is then constructed from seven axioms. It contains classical logic (not many-valued) as a special case. It is first applied to the case where E=[0,1] and V is the identity. The result is a t-norm based many-valued logic in which contradiction can have a nonzero degree of truth but cannot be true; for this reason, this logic is called quasi-paraconsistent

Modification of characters linked to Cucurbita maxima domestication. Using morphometry as a tool for identification

El objetivo de este trabajo consiste en reconocer patrones de variación morfométrica –mediante la aplicación de análisis multivariado para tamaño y forma- en semillas de C. maxima que sean diagnósticos para formas domesticadas, silvestres e híbridas actuales, a fin de aplicarlos a la identificación de semillas arqueológicas. Para lograr este objetivo se midieron con calibre digital 1317 semillas de las formas antedichas y de nueve sitios arqueológicos de Argentina y Perú. Se exploró el patrón de variación entre las mismas en tamaño y forma mediante análisis multivariado. Se identificó una tendencia general hacia la disminución de la variabilidad en forma y tamaño a lo largo del tiempo, con una primera etapa donde se mantuvieron ejemplares híbridos, generándose nuevas formas y una segunda donde se mantuvieron los rasgos de momentos previos y el aumento del tamaño de las semillas

Avaluació de nous algorismes per a la creació de camins entre nodes de la xarxa TOR

En este proyecto se presenta un estudio y una implementación sobre estrategias de selección de nodos de la red TOR. Para esto en una primera parte teorica se da a conocer todo lo que comportan las redes anónimas y su implementación en diferentes entornos. A continuación se estudian los requerimientos y la viabilidad del proyecto. Finalmente exponemos el diseño y desarrollo de los distintos algoritmos propuestos juntamente con las pruebas realizadas y las conclusiones a las que se ha llegado.En aquest projecte es presenta un estudi i una implementació sobre estratègies de selecció de nodes de la xarxa TOR. Per això es mostra en una primera part teòrica on es dóna a conèixer tot el que comporten les xarxes anònimes i la seva implantació en diferents entorns. A continuació s'estudien els requeriments i viabilitat del projecte. Finalment exposem el disseny i desenvolupament dels diferents algorismes proposats juntament amb les proves realitzades i les conclusions a les que s'ha arribat.This project presents a study and an implementation on selection strategies TOR network nodes. For this reason, we present in a first theoretical part wich is made known all that behave anonymous networks and it's implementation in different environments. Here we study the requirements and viability of the project. Finally we discuss the design and development of individual proposed algorithms together with the testing results and conclusions we have reached

Fundamentals of methanol synthesis on metal carbide based catalysts: activation of CO2 and H2

CO2 hydrogenation to methanol and other alcohols constitutes an appealing route to recycle the large amount accumulated in the atmosphere through fossil-derived fuels burning. However, CO2 high chemical stability makes the overall process difficult and appropriate catalysts are needed. Transition metal carbides, either as active phase or as a support for noble metal clusters, have been shown to be able to activate CO2. Here, the mechanism involved in the decomposition of H2 and CO2 on many early transition metal carbides (TMC) surfaces is analyzed with the help of density functional theory (DFT) based calculations complemented by key experiments. Results show that H2 dissociation on VC and δ-MoC is unlikely, that TiC and ZrC are more reactive leading to an exothermic but activated process and that the C:Mo ratio is determinant factor since H2 dissociation on β-Mo2C(001) surface is even more exothermic. The DFT based calculations also show that CO2 adsorption on TMC results in an activated species with TMC→CO2 charge transfer, C-O bond elongations and OCO bending. Supporting Cu4 and Au4 clusters on TMC(001) surfaces leads to more active catalysts due to the induced charge polarization. For H2 dissociation, TiC appears to be the best support, enhancing H2 both thermodynamics and kinetics. CO2 is strongly adsorbed on supported Cu4 and Au4 clusters, and the adsorption energy strength correlates with the methanol formation rate: Cu4/TiC(001) > Au4/TiC(001) > Cu/ZnO(001) >> Cu(111), thus providing potential alternative catalysts for methanol synthesis, in principle dozens of times better than commercial Cu/ZnO based catalysts

Effect of the surface charge discretization on electric double layers. A Monte Carlo simulation study

The structure of the electric double layer in contact with discrete and continuously charged planar surfaces is studied within the framework of the primitive model through Monte Carlo simulations. Three different discretization models are considered together with the case of uniform distribution. The effect of discreteness is analyzed in terms of charge density profiles. For point surface groups,a complete equivalence with the situation of uniformly distributed charge is found if profiles are exclusively analyzed as a function of the distance to the charged surface. However, some differences are observed moving parallel to the surface. Significant discrepancies with approaches that do not account for discreteness are reported if charge sites of finite size placed on the surface are considered

Habitat Constraints in Epikarstic Waters of an Iberian Peninsula Cave System

14 páginas, 6 figuras, 11 tables et al..The epikarstic waters of a restricted sector of the Ojo Guareña cave (north Iberian Peninsula) were investigated to characterize the physico-chemical variation in an annual cycle, to improve the scarce knowledge of the aquatic cave fauna on the Iberian Peninsula, to look for distribution patterns of species per habitat along the annual cycle, and to search for the environmental basis (either physico- or hydro-geochemical) that could explain species distribution in the epikarst. The habitats studied included all puddles and gours present in the sector selected making a total of 51 chemical and 42 biological samples for the entire cycle. The waters show no appreciable contaminationand exhibit small chemical variations throughout the year which are patently affected by external weather conditions. The 53 taxa found belong to ten higher taxonomic groups (Oligochaeta, Turbellaria, Mollusca, Copepoda, Ostracoda, Isopoda, Bathynellacea, Tardigrada, Acarina and Cnidaria), and consist mainly of crustacea with a total of 27 species. Fourteen species were stygobionts (belonging to ten genera), nine of which are new to science and ten of which are endemic. Cave pools that appeared to be more stable in terms of water volume and mineralization, had a lower pCO2 and were carbonate oversaturated, harboured the greatest number of taxa. It is these pools that can maintain strictly cave dwelling species. Pools with lower levels of mineralization and greater water volume fluctuations had a lower diversity of fauna and in general lacked stygobiotic species.Projects PASCALIS EVK2-CT-2001-00121; Convenio Junta de Castilla y León-CSIC (2002-2004) and BTE2002-04492-C02-02.Peer reviewe

Multiscale thermo-mechanical analysis of multi-layered coatings in solar thermal applications

Solar selective coatings can be multi-layered materials that optimize the solar absorption while reducing thermal radiation losses, granting the material long-term stability. These layers are deposited on structural materials (e.g., stainless steel, Inconel) in order to enhance the optical and thermal properties of the heat transfer system. However, interesting questions regarding their mechanical stability arise when operating at high temperatures. In this work, a full thermo-mechanical multiscale methodology is presented, covering the nano-, micro-, and macroscopic scales. In such methodology, fundamental material properties are determined by means of molecular dynamics simulations that are consequently implemented at the microstructural level by means of finite element analyses. On the other hand, the macroscale problem is solved while taking into account the effect of the microstructure via thermo-mechanical homogenization on a representative volume element (RVE). The methodology presented herein has been successfully implemented in a reference problem in concentrating solar power plants, namely the characterization of a carbon-based nanocomposite and the obtained results are in agreement with the expected theoretical values, demonstrating that it is now possible to apply successfully the concepts behind Integrated Computational Materials Engineering to design new coatings for complex realistic thermo-mechanical applications