Pyramidal values

We propose a new type of values for cooperative TU-games, which we call pyramidal values. Assuming that the grand coalition is sequentially formed, and all orderings are equally likely, we define a pyramidal value to be any expected payoff in which the entrant player receives a salary and the right to get part of the benefits derived from subsequent incorporations to the just formed coalition, whereas the remaining benefit is distributed among the incumbent players. To be specific, we consider some parametric families of pyramidal values: the egalitarian pyramidal family, which coincides with the a-consensus value family introduced by Ju et al. in (2007), the proportional pyramidal family, and the weighted pyramidal family, which in turn includes the other two families as special cases. We also analyze the properties of these families, as well as their relationships with other previously defined values.This research has been supported by I+D+i research project MTM2011-27892 from the Government of Spain

The Shapley group value

Following the original interpretation of the Shapley value (Shapley, 1953a) as a priori evaluation of the prospects of a player in a multi-person iteraction situation, we propose a group value, which we call the Shapley group value, as a priori evaluation of the prospects of a group of players in a coalitional game when acting as a unit. We study its properties and we give an axiomatic characterization. We motivate our proposal by means of some relevant applications of the Shapley group value, when it is used as an objective function by a decision maker who is trying to identify an optimal group of agents in a framework in which agents interact and the attained benefit can be modeled by means of a transferable utility game. As an illustrative example we analyze the problem of identifying the set of key agents in a terrorist network.This research has been supported by I+D+i research project MTM2011-27892 from the Government of Spai

Pyramidal values

We propose and analyze a new type of values for cooperative TU-games, which we call pyramidal values. Assuming that the grand coalition is sequentially formed, and all orderings are equally likely, we define a pyramidal value to be any expected payoff in which the entrant player receives a salary, and the rest of his marginal contribution to the just formed coalition is distributed among the incumbent players. We relate the pyramidal-type sharing scheme we propose with other sharing schemes, and we also obtain some known values by means of this kind of pyramidal procedures. In particular, we show that the Shapley value can be obtained by means of an interesting pyramidal procedure that distributes nonzero dividends among the incumbents. As a result, we obtain an alternative formulation of the Shapley value based on a measure of complementarity between two players. Finally, we introduce the family of proportional pyramidal values, in which an incumbent receives a dividend in proportion to his initial investment, measured by means of his marginal contribution

A game theoretic approach to group centrality

This paper is centered in the valuation of the centrality of groups following aproblem-specific approach (Friedkin, 1991). Assuming a TU-game that reflects theinterests which motivate the interactions among individuals in a network, we extend thegame theoretic centrality measure of Gomez et al. (2003) to the case of groups, anddefine the game theoretic group centrality of a group as the variation of its value orpower due to their social relations. We rely on the Shapley group value (Flores et al.,2014) for measuring the value of a group in a game without any restriction, and weintroduce the Myerson group value in order to measure the value when the socialstructure is considered.This research has been supported by I+D+i research project MTM2011-27892 from the Government of Spai

MLContext: A Context-Modeling Language for Context-Aware Systems

Context awareness refers to systems that can both sense and react based on their environment. The complexity of these systems makes necessary to apply software engineering techniques in their development, such as Model-Driven Software development (MDD). One of the main difficulties that developers of context-aware systems must tackle is how to manage the needed context information. In this paper, we present MLContext, a textual Domain Specific Language (DSL) which is specially tailored for modeling context information and automatically generating software artefacts from context models. It has been designed to provide a high-level abstraction, to be an easy to learn, and to promote reuse of context models. We have built a toolkit including an editor and a parser to convert MLContext textual specifications into models. As a proof of concept, we have automatically generated ontologies and Java code for the OCP middleware. MLContext models can be reused in applications with the same context because they do not include details related to the platforms or the implementation. These context models can be specified by non-developers users because MLContext provides high-level abstractions of the domain

Useful Life of Prescribed Fires in a Southern Mediterranean Basin: An Application to Pinus pinaster Stands in the Sierra Morena Range

Prescribed fire is a globally relevant fuel treatment for surface fuel management and wildfire hazard reduction. However, Mediterranean ecosystems are adapted to low and moderate fires; hence, the useful life of prescribed fires is limited. Useful life is defined as the effective rotation length of prescribed fires to mitigate fire spread based on critical surface intensity for crown combustion. In this sense, the useful life of a prescribed fire focuses on surface fuel dynamics and its potential fire behavior. In Pinus pinaster stands, the useful life can be established between 0 and 4 years. Canopy base height, time elapsed from the burning, postfire precipitation, and fine fuel moisture content during the burning were identified as the most important variables in postburn fuel dynamics. Other stand characteristics and postfire precipitation can improve the fine fuel and live fuel dynamics models. Our findings support prescribed fires as an effective fuel treatment in the medium term for forest fire prevention, according to stand characteristics and burning implementation conditions. In this sense, forest managers can use the proposed decision tree to identify the useful life of each prescribed fire based on fine fuel moisture content during burning implementation

Fire ignition patterns to manage prescribed fire behavior: Application to Mediterranean pine forests

Climate change and the accumulation of surface fuel are leading to global changes in the occurrence of increasingly severe fires. In light of current budgetary constraints, prescribed fire can be a very cost-efficient tool for both reducing wildfire hazards and managing fire-prone landscapes. However, despite its widespread use in some countries, social and administrative constraints arise when applied at the European or larger scales. Science-based knowledge concerning fire behavior, fuel load reduction, and tree impacts is required to support the use of prescribed fire. Spatial ignition patterns can increase or decrease the spread rate, flame length, and flame residence time according to the objectives of a prescribed fire. This work aims to analyze fire behavior using different fire ignition patterns (strip-heading fire, flanking fire, and spot-heading fire) and meteorological and fuel conditions. Seventy-seven observations or sampling units using twenty-three prescribed fires were established for fire monitoring. Non-linear models based on environmental variables were fitted for the spread rate and flame length. Our study proposes a novel way of sharing scientific knowledge in relation to the most common distances between ignition lines and ignition points used in the southern Iberian Peninsula. The spread rate and flame length can be increased in strip-heading fire, by more than 3.5-fold and more than 1.95-fold, respectively, by modifying only the distance between ignition lines. Flanking fire could lead to a decrease in the spread rate by approximately half. Although spot-heading fire can reduce the spread rate by more than 78% and flame length by more than 41%, the highest distances between points could increase the flame residence time by 39–132%. This research seeks to achieve a trade-off between fire intensity and the impacts of fire on trees, soil, and surface roots

An ecophysiographic approach for Araucaria araucana regeneration management

Chilean temperate forests are dominated by Nothofagus and Araucaria araucana species. Despite A. araucana not being at imminent risk of extinction, its cultural value and the associated environmental services and landscape goods have an important role for the conservation of this native forest. In some areas, the future conservation of A. araucana is a cause of great concern given its management prohibition and regeneration limitation due to slow growth, canopy tree competition and dense understory. The above characteristics make this species most susceptible to some disturbances, such as livestock, wildlife and human pressures. Therefore, sustainable management of A. araucana forests requires the assessment of its regeneration condition. The objective of this research was to apply multivariable analysis techniques in search of the most relevant parameter for Araucaria regeneration. This study used the following methods: principal component analysis (PCA), forward stepwise regression modeling and Maxent modeling. By PCA, it was possible to reduce the dimension to six-dimensional with a variance explanation of greater than 75%. The multivariable regression model, known as model 7, was the best compromise between the coefficient of determination and model size (number of independent variables). Incorporating a maximum entropy trend improved model performance. A spatial prediction was obtained by summing the contributions of statistical methods and the geographic information system (GIS). The GIS increased the flexibility of the proposed model, which enabled an extrapolation to other areas at different spatial and temporal scales