Measuring the efficiency in Spanish municipal refuse collection services

The objective of this study is to analyse the technical or productive efficiency ofthe refuse collection services in 75 municipalities located in the Spanish regionof Catalonia. The analysis has been carried out using various techniques. Firstly we have calculated a deterministic parametric frontier, then a stochastic parametric frontier, and finally, various non-parametric approaches (DEA and FDH). Concerning the results, these naturally differ according to the technique used to approach the frontier. Nevertheless, they have an appearance of solidity, at least with regard to the ordinal concordance among the indices of efficiency obtained by the different approaches, as is demonstrated by the statistical tests used. Finally, we have attempted to search for any relation existing between efficiency and the method (public or private) of managing the services. No significant relation was found between the type of management and efficiencyindices

Domain Adaptation in remote sensing: increasing the portability of land-cover classifiers

Among the types of remote sensing acquisitions, optical images are certainly one of the most widely relied upon data sources for Earth observation. They provide detailed measurements of the electromagnetic radiation reflected or emitted by each pixel in the scene. Through a process termed supervised land-cover classification, this allows to automatically yet accurately distinguish objects at the surface of our planet. In this respect, when producing a land-cover map of the surveyed area, the availability of training examples representative of each thematic class is crucial for the success of the classification procedure. However, in real applications, due to several constraints on the sample collection process, labeled pixels are usually scarce. When analyzing an image for which those key samples are unavailable, a viable solution consists in resorting to the ground truth data of other previously acquired images. This option is attractive but several factors such as atmospheric, ground and acquisition conditions can cause radiometric differences between the images, hindering therefore the transfer of knowledge from one image to another. The goal of this Thesis is to supply remote sensing image analysts with suitable processing techniques to ensure a robust portability of the classification models across different images. The ultimate purpose is to map the land-cover classes over large spatial and temporal extents with minimal ground information. To overcome, or simply quantify, the observed shifts in the statistical distribution of the spectra of the materials, we study four approaches issued from the field of machine learning. First, we propose a strategy to intelligently sample the image of interest to collect the labels only in correspondence of the most useful pixels. This iterative routine is based on a constant evaluation of the pertinence to the new image of the initial training data actually belonging to a different image. Second, an approach to reduce the radiometric differences among the images by projecting the respective pixels in a common new data space is presented. We analyze a kernel-based feature extraction framework suited for such problems, showing that, after this relative normalization, the cross-image generalization abilities of a classifier are highly increased. Third, we test a new data-driven measure of distance between probability distributions to assess the distortions caused by differences in the acquisition geometry affecting series of multi-angle images. Also, we gauge the portability of classification models through the sequences. In both exercises, the efficacy of classic physically- and statistically-based normalization methods is discussed. Finally, we explore a new family of approaches based on sparse representations of the samples to reciprocally convert the data space of two images. The projection function bridging the images allows a synthesis of new pixels with more similar characteristics ultimately facilitating the land-cover mapping across images.

Factors influencing privatization of urban solid waste collection: some evidence from Spain

In this paper we analyse some of the organisational aspects of the urban solid waste collection and, in particular, the privatization modality of contracting out. We start by discussing some of the theoretical aspects of contracting out. We then specify and estimate an explanatory model on a sample of municipalities that we surveyed. Our purpose is twofold: on the one hand, we identify the economic factors at work when deciding to contract out the service and, on the other hand, we analyse the role of ideological factors in choosing between the public production of the service or contracting it out. The results show a significant effect of the demand for waste collection on contracting out. There also appears to be a neighbouring effect as the municipalities close to other cities that contract out are also more prone to do so. Finally, the decisions to contract seem to have been motivated by pragmatic rather than ideological reasons.

Heterogeneous discounting in consumption-investment problems. Time consistent solutions

[cat] En aquest treball s'analitza un model estocàstic en temps continu en el que l'agent decisor descompta les utilitats instantànies i la funció final amb taxes de preferència temporal constants però diferents. En aquest context es poden modelitzar problemes en els quals, quan el temps s'acosta al moment final, la valoració de la funció final incrementa en comparació amb les utilitats instantànies. Aquest tipus d'asimetria no es pot descriure ni amb un descompte estàndard ni amb un variable. Per tal d'obtenir solucions consistents temporalment es deriva l'equació de programació dinàmica estocàstica, les solucions de la qual són equilibris Markovians. Per a aquest tipus de preferències temporals, s'estudia el model clàssic de consum i inversió (Merton, 1971) per a les funcions d'utilitat del tipus CRRA i CARA, comparant els equilibris Markovians amb les solucions inconsistents temporalment. Finalment es discuteix la introducció del temps final aleatori.

Measuring the efficiency in Spanish municipal refuse collection services

The objective of this study is to analyse the technical or productive efficiency ofthe refuse collection services in 75 municipalities located in the Spanish regionof Catalonia. The analysis has been carried out using various techniques. Firstly we have calculated a deterministic parametric frontier, then a stochastic parametric frontier, and finally, various non-parametric approaches (DEA and FDH). Concerning the results, these naturally differ according to the technique used to approach the frontier. Nevertheless, they have an appearance of solidity, at least with regard to the ordinal concordance among the indices of efficiency obtained by the different approaches, as is demonstrated by the statistical tests used. Finally, we have attempted to search for any relation existing between efficiency and the method (public or private) of managing the services. No significant relation was found between the type of management and efficiencyindices

Sequential decisions in allocation problems

[eng] In the context of cooperative TU-games, and given an order of players, we consider the problem of distributing the worth of the grand coalition as a sequentia decision problem. In each step of process, upper and lower bounds for the payoff of the players are required related to successive reduced games. Sequentially compatible payoffs are defined as those allocation vectors that meet these recursive bounds. The core of the game is reinterpreted as a set of sequentally compatible payoffs when the Davis-Maschler reduced game is considered (Th.1). Independently of the reduction, the core turns out to be the intersections of the family of the sets of sequentially compatible payoffs corresponding to the different possible orderings (Th.2), so it is in some sense order-independent. Finally, we analyze advantagenous properties for the first player

Some fundamental aspects of palentological methodology: its problems and incidence

Two trends which presently exist in relation to the concept of Paleontology are analyzed, pointing out some of the aspects which negative influence. Various reflections are made based on examples of some of the principal points of paleontological method, such as the influence of a punctual sampling, the meaning of size-frequency distribution and subjectivity in the identification of fossils. Topics which have a marked repercussion in diverse aspects of Paleontology are discussed.