Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.

On p-optimal proof systems and logics for PTIME

"Vegeu el resum a l'inici del document del fitxer adjunt"

Moderating effects of management control systems and innovation on performance. Simple methods for correcting the effects of measurement error for interaction effects in small samples

In the accounting literature, interaction or moderating effects are usually assessed by means of OLS regression and summated rating scales are constructed to reduce measurement error bias. Structural equation models and two-stage least squares regression could be used to completely eliminate this bias, but large samples are needed. Partial Least Squares are appropriate for small samples but do not correct measurement error bias. In this article, disattenuated regression is discussed as a small sample alternative and is illustrated on data of Bisbe and Otley (in press) that examine the interaction effect of innovation and style of use of budgets on performance. Sizeable differences emerge between OLS and disattenuated regression

On the origins of electoral systems and political parties. The role of elections in multi-member districts

The old, understudied electoral system composed of multi-member districts, open ballot and plurality rule is presented as the most remote scene of the origin of both political parties and new electoral systems. A survey of the uses of this set of electoral rules in different parts of the world during remote and recent periods shows its wide spread. A model of voting by this electoral system demonstrates that, while it can produce varied and pluralistic representation, it also provides incentives to form factional or partisan candidacies. Famous negative reactions to the emergence of factions and political parties during the 18th and 19th centuries are reinterpreted in this context. Many electoral rules and procedures invented since the second half of the 19th century, including the Australian ballot, single-member districts, limited and cumulative ballots, and proportional representation rules, derived from the search to reduce the effects of the originating multi-member district system in favor of a single party sweep. The general relations between political parties and electoral systems are restated to account for the foundational stage here discussed.

Hybrid turbo FEC/ARQ systems and distributed space-time coding for cooperative transmission

Cooperative transmission can be seen as a "virtual" MIMO system, where themultiple transmit antennas are in fact implemented distributed by the antennas both at the source and the relay terminal. Depending on the system design, diversity/multiplexing gainsare achievable. This design involves the definition of the type of retransmission (incrementalredundancy, repetition coding), the design of the distributed space-time codes, the errorcorrecting scheme, the operation of the relay (decode&forward or amplify&forward) and thenumber of antennas at each terminal. Proposed schemes are evaluated in different conditionsin combination with forward error correcting codes (FEC), both for linear and near-optimum(sphere decoder) receivers, for its possible implementation in downlink high speed packetservices of cellular networks. Results show the benefits of coded cooperation over directtransmission in terms of increased throughput. It is shown that multiplexing gains areobserved even if the mobile station features a single antenna, provided that cell wide reuse of the relay radio resource is possible.

Settlement evolution, field systems and sedimentary processes in a Mediterranean mid-mountain (Montseny Massif, Catalunya)

This paper presents the first results of a current research project about human – environmental interactions in the Montseny Massif. Our work sets out to integrate two research lines in the studied area: - Archaeological and archaeo-morphological surveys in a lower part of the mountains in order to characterize the evolution of the settlements and field systems. - The geological and geomorphological characterization of the slope and terrace deposits in relation with field systems and archaeological data. First results point out the intensive occupation of these inland areas during the Iberian and the Roman periods. Post-Roman sediments show different processes of erosion.

Landscape Systems and Human Land-Use Interactions in Mediterranean Highlands and Littoral Plains during the Late Holocene: Integrated Analysis from the InterAmbAr Project (North-Eastern Catalonia).

The main goal of the InterAmbAr reseach project is to analyze the relationships between landscape systems and human land-use strategies on mountains and littoral plains from a long-term perspective. The study adopts a high resolution analysis of small-scale study areas located in the Mediterranean region of north-eastern Catalonia. The study areas are distributed along an altitudinal transect from the high mountain (above 2000m a.s.l.) to the littoral plain of Empordà (Fig. 1). High resolution interdisciplinary research has been carried out from 2010, based on the integration of palaeoenvironmental and archaeological data. The micro-scale approach is used to understand human-environmental relationships. It allows better understanding of the local-regional nature of environmental changes and the synergies between catchment-based systems, hydro-sedimentary regimes, human mobility, land-uses, human environments, demography, etc.

Landscape context on generalist and specialist aphid natural enemies

Report for the scientific sojourn at the University of Lund, Sweden, between May and September 2007. A landscape-scale research approach has been highlighted by a growing body of literature as essential for understanding important ecosystem services as biological control. Aphids are victims of a diversity of enemies making the aphid-enemy interaction a nice example for the role of enemy diversity for the functioning of biological control. Here it is examined the effects of landscape complexity on cereal aphids and associated natural enemies that varied in the degree of specialization. Parasitoids wasps abundance did not differ between landscape types but was strongly negatively related to the percentage of arable land. In contrast, abundances of generalist predators like Coccinellidae were significantly higher in simple landscapes since can benefit from the high availability of a variety of alternative resources within cropping systems. Consequently coccinellidae-to-aphid ratio was significantly higher in fields in homogenous landscapes as compared to fields included in an heterogeneous landscape, suggesting that enemy pressure on cereal aphids increases with landscape simplification. The landscape effect will depend mainly on the degree of specialization of functionally dominant natural enemies, so that the results imply that conservation actions aiming to optimise abundance for one taxonomic group in the agricultural landscape will not automatically increase abundance of other groups. Given that the strength of natural enemy impact on biocontrol depends on landscape features and the role of functionally dominant natural enemies. So, therefore it is essential to focus the future empirical work in examining the schedule of agricultural landscapes that maintain a diversity of generalist and specialist natural enemies.

La permacultura en la gestión del agua: el caso de Can Valldaura

El presente trabajo se centra en el análisis del ciclo del Agua en la finca de Can Valldaura, en el municipio de Cerdanyola, dentro del Parc de Collserola. El IAAC (Instituto de Arquitectura Avanzada de Cataluña), organismo gestor, pretende estudiar e investigar sobre el término de la autosuficiencia, volviendo a dinamizar entre otros aspectos las funciones agrícolas y ganaderas de la finca. El objetivo principal de este estudio es hacer propuestas en la gestión del agua bajo los principios de la Permacultura en la finca de Can Valldaura, queriendo analizar si es posible alcanzar la autosuficiencia a nivel hídrico realizando el proyecto silvoagroforestal planeado por el IAAC. Una vez calculadas las necesidades hídricas del proyecto de Can Valldaura, y analizadas las entradas y salidas hídricas del sistema, los resultados muestran que las infraestructuras actuales son insuficientes para llevar a cabo el proyecto silvoagroforestal si la autosuficiencia es un objetivo prioritario. En este sentido se proponen distintas medidas de gestión: la restauración del antiguo sistema de drenaje, la construcción de una nueva balsa, y el aprovechamiento de las aguas recogidas por los caminos. Además se proponen sistemas de cultivo que mejorarían la estructura del suelo aumentando la infiltración del agua de la lluvia y su retención. Los datos analizados indican que con las medias de gestión y sistemas de cultivo propuestos el proyecto silvoagroforestal podría llevarse a cabo de forma autosufiente.

Fading models and metrics for contemporary wireless systems

The purpose of this paper is to examine (1) some of the models commonly used to represent fading,and (2) the information-theoretic metrics most commonly used to evaluate performance over those models. We raise the question of whether these models and metrics remain adequate in light of the advances that wireless systems haveundergone over the last two decades. Weaknesses are pointedout, and ideas on possible fixes are put forth.

Nitrogen replacement value of alfalfa to corn and wheat under irrigated Mediterranean conditions

In crop rotations that include alfalfa (Medicago sativa L.), agronomic and environmental concerns mean that it is important to determine the N fertilizer contribution of this legume for subsequent crops in order to help to increase the sustainability of cropping systems. To determine the N fertilizer replacement value (FRV) of a 2-yr alfalfa crop on subsequent crops of corn (Zea mays L.) followed by wheat (Triticum aestivum L.) under irrigated Mediterranean conditions, two 4-yr rotations (alfalfa-corn-wheat and corn-corn-corn-wheat) were conducted from 2001 to 2004 in a Typic Xerofluvent soil. Corn yields were compared after two years of alfalfa and a third year of corn under monoculture and wheat yields were also compared after both rotations. Corn production after alfalfa outyielded monoculture corn at all four rates of N fertilizer application analyzed (0, 100, 200 and 300 kg N/ha). The FRV of 2-yr alfalfa for corn was about 160 kg N/ha. Wheat grown after the alfalfa-corn rotation outyielded that grown after corn under monoculture at both the rates of N studied (0 and 100 kg N/ha). The FRV of alfalfa for wheat following alfalfa-corn was about 76 kg N/ha. Soil NO3 -N content after alfalfa was greater than with the corn monoculture at all rates of N fertilizer application and this higher value persisted during the second crop after alfalfa. This was probably one of the reasons for the better yields associated with the alfalfa rotation. These results make a valuable contribution to irrigated agriculture under mediterranean conditions, show reasons for interest in rotating alfalfa with corn, and explain how it is possible to make savings when applying N fertilizer.

WePreserve 2009: DPE/Planets/CASPAR/nestor Joint Training Event: The Preservation challenge: basic concepts and practical applications (Barcelona, 23-27 març 2009)

Reseña del congreso WePreserve 2009 que tuvo lugar los pasados 23 al 27 de marzo en Barcelona, organizadopor la Facultad de Biblioteconomía y Documentación de la Universitat de Barcelona, con la colaboración del Institut d'Estudis Catalans, la Biblioteca de Catalunya y el Consorci de Biblioteques de Barcelona. El seminario 2009 WePreserve se celebra anualmente desde el año 2007 y participan todas las figuras de referencia europeas en materia de investigación en sistemas y metodologías que garantizan la preservación digital de los documentos: Digital Preservation Europe (DPE), Preservation and Long-term Access Through Networked Services (Planets), Cultural Artistic and Scientific Knowledge for Preservation, Access and Retrieval (CASPAR), y Network of expertise in Digital long-term preservation (nestor).

Application for fault location in electrical power distribution systems

Fault location has been studied deeply for transmission lines due to its importance in power systems. Nowadays the problem of fault location on distribution systems is receiving special attention mainly because of the power quality regulations. In this context, this paper presents an application software developed in Matlabtrade that automatically calculates the location of a fault in a distribution power system, starting from voltages and currents measured at the line terminal and the model of the distribution power system data. The application is based on a N-ary tree structure, which is suitable to be used in this application due to the highly branched and the non- homogeneity nature of the distribution systems, and has been developed for single-phase, two-phase, two-phase-to-ground, and three-phase faults. The implemented application is tested by using fault data in a real electrical distribution power system