Una exploración completa de los costes de servicio de residuos sólidos

La literatura económica sobre los servicios municipales de residuos sólidos en España es muy escasa, aun cuando estos servicios han sido objeto d'intensas reformas organizativas y regulatorias. En esta investigación se estudia su estructura de costes con el objetivo de explicar la variabilidad entre los municipios de los costes soportados por el servicio. Se determina una función de costes y se estima de forma paramétrica. Los resultados del análisis empírico permiten estudiar la existencia de economías de escala con el output, y el efecto de algunos factores directamente asociados con el servicio como el grado de residuos selectivos, la frecuencia de recogida o la existencia de instalaciones de depósito en el municipio. Además, se analiza el impacto sobre los costes de otros factores como la densidad de población, los niveles salariales, la estacionalidad y la forma de producción, pública o privada.

Extent and limitations of density functional theory in describing magnetic systems

The performance of density-functional theory to solve the exact, nonrelativistic, many-electron problem for magnetic systems has been explored in a new implementation imposing space and spin symmetry constraints, as in ab initio wave function theory. Calculations on selected systems representative of organic diradicals, molecular magnets and antiferromagnetic solids carried out with and without these constraints lead to contradictory results, which provide numerical illustration on this usually obviated problem. It is concluded that the present exchange-correlation functionals provide reasonable numerical results although for the wrong physical reasons, thus evidencing the need for continued search for more accurate expressions.

Electronic and magnetic structure of LaMnO3 from hybrid periodic density-functional theory

The electronic and magnetic structures of the LaMnO3 compound have been studied by means of periodic calculations within the framework of spin polarized hybrid density-functional theory. In order to quantify the role of approximations to electronic exchange and correlation three different hybrid functionals have been used which mix nonlocal Fock and local Dirac-Slater exchange. Periodic Hartree-Fock results are also reported for comparative purposes. The A-antiferromagnetic ground state is properly predicted by all methods including Hartree-Fock exchange. In general, the different hybrid methods provide a rather accurate description of the band gap and of the two magnetic coupling constants, strongly suggesting that the corresponding description of the electronic structure is also accurate. An important conclusion emerging from this study is that the nature of the occupied states near the Fermi level is intermediate between the Hartree-Fock and local density approximation descriptions with a comparable participation of both Mn and O states.

Surface structure and stability of PdZn and PtZn alloys: Density-functional slab model studies

Geometric parameters of binary (1:1) PdZn and PtZn alloys with CuAu-L10 structure were calculated with a density functional method. Based on the total energies, the alloys are predicted to feature equal formation energies. Calculated surface energies of PdZn and PtZn alloys show that (111) and (100) surfaces exposing stoichiometric layers are more stable than (001) and (110) surfaces comprising alternating Pd (Pt) and Zn layers. The surface energy values of alloys lie between the surface energies of the individual components, but they differ from their composition weighted averages. Compared with the pure metals, the valence d-band widths and the Pd or Pt partial densities of states at the Fermi level are dramatically reduced in PdZn and PtZn alloys. The local valence d-band density of states of Pd and Pt in the alloys resemble that of metallic Cu, suggesting that a similar catalytic performance of these systems can be related to this similarity in the local electronic structures.

Antiferromagnetic exchange interactions from hybrid density functional theory

A hybrid theory which combines the full nonlocal ¿exact¿ exchange interaction with the local spin-density approximation of density-functional theory is shown to lead to marked improvement in the description of antiferromagnetically coupled systems. Semiquantitative agreement with experiment is found for the magnitude of the coupling constant in La2CuO4, KNiF3, and K2NiF4. The magnitude of the unpaired spin population on the metal site is in excellent agreement with experiment for La2CuO4.

Extent and limitations of density functional theory in describing magnetic systems

The performance of density-functional theory to solve the exact, nonrelativistic, many-electron problem for magnetic systems has been explored in a new implementation imposing space and spin symmetry constraints, as in ab initio wave function theory. Calculations on selected systems representative of organic diradicals, molecular magnets and antiferromagnetic solids carried out with and without these constraints lead to contradictory results, which provide numerical illustration on this usually obviated problem. It is concluded that the present exchange-correlation functionals provide reasonable numerical results although for the wrong physical reasons, thus evidencing the need for continued search for more accurate expressions.

Rockfall travel distance analysis by using empirical models (Solà d'Andorra la Vella, Central Pyrenees)

The prediction of rockfall travel distance below a rock cliff is an indispensable activity in rockfall susceptibility, hazard and risk assessment. Although the size of the detached rock mass may differ considerably at each specific rock cliff, small rockfall (<100 m3) is the most frequent process. Empirical models may provide us with suitable information for predicting the travel distance of small rockfalls over an extensive area at a medium scale (1:100 000¿1:25 000). "Solà d'Andorra la Vella" is a rocky slope located close to the town of Andorra la Vella, where the government has been documenting rockfalls since 1999. This documentation consists in mapping the release point and the individual fallen blocks immediately after the event. The documentation of historical rockfalls by morphological analysis, eye-witness accounts and historical images serve to increase available information. In total, data from twenty small rockfalls have been gathered which reveal an amount of a hundred individual fallen rock blocks. The data acquired has been used to check the reliability of the main empirical models widely adopted (reach and shadow angle models) and to analyse the influence of parameters which affecting the travel distance (rockfall size, height of fall along the rock cliff and volume of the individual fallen rock block). For predicting travel distances in maps with medium scales, a method has been proposed based on the "reach probability" concept. The accuracy of results has been tested from the line entailing the farthest fallen boulders which represents the maximum travel distance of past rockfalls. The paper concludes with a discussion of the application of both empirical models to other study areas.

Conditional predictive density evaluation in the presence of instabilities

We propose new methods for evaluating predictive densities. The methods includeKolmogorov-Smirnov and Cram?r-von Mises-type tests for the correct specification ofpredictive densities robust to dynamic mis-specification. The novelty is that the testscan detect mis-specification in the predictive densities even if it appears only overa fraction of the sample, due to the presence of instabilities. Our results indicatethat our tests are well sized and have good power in detecting mis-specification inpredictive densities, even when it is time-varying. An application to density forecastsof the Survey of Professional Forecasters demonstrates the usefulness of the proposedmethodologies.

Empirical study about the effects of the application of IAS 32 in Cooperatives

Objecte: L'aplicació de la NIC 32 en les cooperatives ha generat una important controvèrsia en els últims anys. Fins al moment, s'han realitzat diversos treballs que intenten preveure els possibles efectes de la seva aplicació. Aquest treball pretén analitzar l'impacte de la primera aplicació de la NIC 32 en el sector cooperatiu. Disseny/metodologia/enfocament: S'ha seleccionat una mostra de 98 cooperatives, i s'ha realitzat una anàlisi comparativa de la seva informació financera presentada abans i després de l'aplicació de la NIC 32, per a determinar les diferències existents. S’ha utilitzat la prova de la suma de rangs de Wilcoxon per comprovar si aquestes diferències són significatives. També s’ha utilitzat la prova de la U de Mann Whitney per comprovar si existeixen diferències significatives en l’impacte relatiu de l’aplicació de la NIC 32 entre diversos grups de cooperatives. Finalment, s'ha realitzat una anàlisi dels efectes de l'aplicació de la NIC 32 en la situació patrimonial i econòmica de les cooperatives, i en l'evolució dels seus actius intangibles, mitjançant l’ús de tècniques d’anàlisi econòmico-financera. Aportacions i resultats: Els resultats obtinguts confirmen que l'aplicació de la NIC 32 provoca diferències significatives en algunes partides del balanç de situació i el compte de pèrdues i guanys, així com en les ràtios analitzades. Les principals diferències es concreten en una reducció del nivell de capitalització i un augment de l'endeutament de les cooperatives, així com un empitjorament general dels ràtios de solvència i autonomia financera. Limitacions: Cal tenir en compte que el treball s'ha realitzat amb una mostra de cooperatives que estan obligades a auditar els seus comptes anuals. Per tant, els resultats obtinguts han d'interpretar-se en un context de cooperatives de tamany elevat. També cal tenir en compte que hem realitzat una anàlisi comparativa dels comptes anuals de 2011 i 2010. Això ens ha permès conèixer les diferències en la informació financera de les cooperatives abans i després d'aplicar la NIC 32. Encara que algunes d’aquestes diferències també podrien estar causades per altres factors com la situació econòmica, els canvis en l'aplicació de les normes comptables, etc. Originalitat/valor afegit: Creiem que és el moment idoni per a realitzar aquest treball d'investigació, ja que des de 2011 totes les cooperatives espanyoles han d'aplicar les normes comptables adaptades a la NIC 32. A més, fins on coneixem, no existeixen altres treballs similars realitzats amb comptes anuals de cooperatives que ja han aplicat les normes comptables adaptades a la NIC 32 . Creiem que els resultats d'aquest treball d'investigació poden ser útils per a diferents grups d'interès. En primer lloc, perquè els organismes emissors de normes comptables puguin conèixer l'abast de la NIC 32 en les cooperatives i, puguin plantejar millores en el contingut de la norma. En segon lloc, perquè les pròpies cooperatives, federacions, confederacions i altres organismes cooperatius disposin d'informació sobre l'impacte econòmic de la primera aplicació de la NIC 32, i puguin realitzar les valoracions que creguin convenients. I en tercer lloc, perquè les entitats financeres, auditors i assessors de cooperatives i altres grups d'interès disposin d'informació sobre els canvis en els comptes anuals de les cooperatives, i puguin tenir-los en compte a l'hora de prendre decisions. Paraules clau: Cooperatives, patrimoni net, capital social, NIC 32, solvència, efectes de la normativa comptable, informació financera, ràtios.

Traces of functions in Fock spaces on lattices of critical density

Following a scheme of Levin we describe the values that functions in Fock spaces take on lattices of critical density in terms of both the size of the values and a cancelation condition that involves discrete versions of the Cauchy and Beurling-Ahlfors transforms.

Empirical mode decomposition-based face recognition system

In this work we explore the multivariate empirical mode decomposition combined with a Neural Network classifier as technique for face recognition tasks. Images are simultaneously decomposed by means of EMD and then the distance between the modes of the image and the modes of the representative image of each class is calculated using three different distance measures. Then, a neural network is trained using 10- fold cross validation in order to derive a classifier. Preliminary results (over 98 % of classification rate) are satisfactory and will justify a deep investigation on how to apply mEMD for face recognition.

EEG signal analysis via a cleaning procedure based on multivariate empirical mode decomposition

Artifacts are present in most of the electroencephalography (EEG) recordings, making it difficult to interpret or analyze the data. In this paper a cleaning procedure based on a multivariate extension of empirical mode decomposition is used to improve the quality of the data. This is achieved by applying the cleaning method to raw EEG data. Then, a synchrony measure is applied on the raw and the clean data in order to compare the improvement of the classification rate. Two classifiers are used, linear discriminant analysis and neural networks. For both cases, the classification rate is improved about 20%.