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The addition of fibres to concrete is an effective solution for enhancing its post-cracking tensile strength (fctR). Currently, this property is characterized through high-cost and time-consuming experimental tests since no reliable analytical methods exist to predict this mechanical property. This study provides two neural networks for predicting the fctR obtained from flexural beam tests for crack mouth opening displacements of 0.50 mm (fR1) and 2.50 mm (fR3). Network architectures are obtained with an optimization process that involved training 1568 Multi-Layer Perceptron configurations under Monte Carlo cross-validation over 50 iterations, with a total of 78,400 trainings for each fR,i. The resulting models were evaluated using performance metrics including Coefficient of Determination (R2), Correlation Coefficient (CC), Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and Scatter index (SI). High predictive accuracies were achieved for both fR1 (R2 = 0.87, CC = 0.93, MAE = 0.64 MPa, RMSE = 0.90 MPa, SI = 19.2%) and fR3 (R2 = 0.85, CC = 0.92, MAE = 0.73 MPa, RMSE = 0.95 MPa, SI = 19.8%). Furthermore, the analysis of their global and local interpretability through the game-theory-based SHAP explanation method confirms their consistency with established understandings of fibre-reinforced concrete (FRC) behaviour. Moreover, numerical expressions are proposed as an alternative to traditional testing methods, offering a tool to predict the flexural post-cracking tensile strength for pre-design and quality control purposes of FRC structures. These approaches are deemed essential for advancing FRC technology marking a significant advancement in addressing the design limitations and widespread application challenges associated with the material., This work was supported by the Catalan agency AGAUR through its research group support program (2021 SGR 00341) and by the Spanish Ministry of Science and Innovation under the scope of project CREEF (PID2019-108978RB-C32/AEI/10.13039/ 501100011033)., Peer Reviewed, Postprint (author's final draft)

© 2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0, Many real-world voting systems consist of voters that occur in just two different types. Indeed, each voting system with a “House” and a “Senate” is of that type. Here we present structural characterizations and an explicit enumeration formula for these so-called bipartite simple games. This formula extends some partial enumerations of simple games related to completeness or the number of minimal winning coalitions., This paper is part of the project PID2019-104987GB-I00 financed by MCIN/AEI/10.13039/ 501100011033., Postprint (author's final draft)

We survey some recent work of Maria Serna concerning strategic games. We first examine some results related to the formal representation of strategic games and the complexity of problems related to both the existence of equilibria and the equivalence of games. These results provided a better understanding of how the succinctness of the game representation affects the complexity of such problems. We then describe some work dealing with the definition of new strategic games. The study of a Network Formation Game with asymmetric players, and the introduction of Celebrity Games as well as of Strategic Search Games intend to explain the natural behaviour of agents acting in some particular environments like communication networks, social networks, or even networks that contain valuable items hidden in different nodes., This work was partially supported by funds from the AGAUR, Spain of the Government of Catalonia under project ref. 2017 SGR 786 (ALBCOM), by the Spanish Ministry for Economy and Competitiveness (MINECO), Spain and by the European Union (FEDER funds), under grants ref. TIN2017-86727-C2-1-R., Peer Reviewed, Postprint (author's final draft)

Cooperative game theory considers simple games and influence games as essential classes of games. A simple game can be viewed as a model of voting systems in which a single alternative, such as a bill or an amendment, is pitted against the status quo. An influence game is a cooperative game in which a team of players (or coalition) succeeds if it is able to convince sufficiently many agents to participate in a task. Furthermore, influence decision models allow to represent discrete system dynamics as graphs whose nodes are activated according to an influence spread model. It let us to depth in the social network analysis. All these concepts are applied to a wide variety of disciplines, such as social sciences, economics, marketing, cognitive sciences, political science, biology, computer science, among others. In this survey we present different advances in these topics, joint work with M. Serna. These advances include representations of simple games, the definition of influence games, and how to characterize different problems on influence games (measures, values, properties and problems for particular cases with respect to both the spread of influence and the structure of the graph). Moreover, we also present equivalent models to the simple games, the computation of satisfaction and power in collective decision-making models, and the definition of new centrality measures used for social network analysis. In addition, several interesting computational complexity results have been found., Peer Reviewed, Postprint (author's final draft)

Committees with yes-no-decisions are commonly modeled as simple games and the ability of a member to influence the group decision is measured by so-called power indices. For a weighted game we say that a power index satisfies local monotonicity if a player who controls a large share of the total weight vote does not have less power than a player with a smaller voting weight. In (Holler, 1982) Manfred Holler introduced the Public Good index. In its unnormalized version, i.e., the raw measure, it counts the number of times that a player belongs to a minimal winning coalition. Unlike the Banzhaf index, it does not count the remaining winning coalitions in which the player is crucial. Holler noticed that his index does not satisfy local monotonicity, a fact that can be seen either as a major drawback (Felsenthal & Machover, 1998, 221 ff.)or as an advantage (Holler & Napel 2004). In this paper we consider a convex combination of the two indices and require the validity of local monotonicity. We prove that the cost of obtaining it is high, i.e., the achievable new indices satisfying local monotonicity are closer to the Banzhaf index than to the Public Good index. All these achievable new indices are more solidary than the Banzhaf index, which makes them as very suitable candidates to divide a public good. As a generalization we consider convex combinations of either: the Shift index, the Public Good index, and the Banzhaf index, or alternatively: the Shift Deegan-Packel, Deegan-Packel, and Johnston indices., Peer Reviewed, Postprint (author's final draft)

We consider a simple and altruistic multiagent system in which the agents are eager to perform a collective task but where their real engagement depends on the willingness to perform the task of other influential agents. We model this scenario by an influence game, a cooperative simple game in which a team (or coalition) of players succeeds if it is able to convince enough agents to participate in the task (to vote in favor of a decision). We take the linear threshold model as the influence model. We show first the expressiveness of influence games showing that they capture the class of simple games. Then we characterize the computational complexity of various problems on influence games, including measures (length and width), values (Shapley-Shubik and Banzhaf) and properties (of teams and players). Finally, we analyze those problems for some particular extremal cases, with respect to the propagation of influence, showing tighter complexity characterizations., Peer Reviewed, Postprint (author’s final draft)

A scenario-based negotiation (SBN) win-to-win approach is proposed for the optimization of coordinated decentralized multi-site multi-product Supply Chains (SCs) in a competitive environment. Based on non-symmetric roles, the leader aims to settle its offer taking into account the uncertain reaction of the follower, which behavior is represented by a probability of acceptance. Different negotiation scenarios, based on considering Standalone, Cooperative, and Non-Cooperative SCs are analyzed for the negotiation, resulting in different MINLP tactical models, which are illustrated using a case study with different “follower” SCs around an industrial production SC “leader”. On the other hand, a Stackelberg non-cooperative bi-level MINLP game model is built and solved for the same case study. The Non-Cooperative Negotiation Scenario (NCNS) proves to be more adequate, leading to higher global profits expectations., Peer Reviewed, Postprint (published version)

Energy-related costs are becoming one of the largest contributors to the overall cost of operating a data center, whereas the degree of data center utilization continues to be very low. An energy-aware dynamic provision of resources based on the consolidation of existing application instances can simultaneously address the underutilization of servers while greatly reducing energy costs. The economics behind energy costs cannot be treated separately from resource provision and allocation. However, current scheduling techniques based on market mechanisms do not specifically deal with such a scenario. To establish the upper bound of energy savings, we model the problem of minimizing energy consumption when allocating resources to networked applications as a Stackelberg leadership game. The model is applied to a proportional-share mechanism in which resource providers can maximize profit by minimizing energy costs, while users can select resources that ensure that their minimum requirements are satisfied. We show that our mechanism can determine the optimal set of resources switched on and off, while maintaining user service level agreements (SLAs) — even in realistic conditions considering incomplete information, Peer Reviewed, Postprint (published version)

Some distinguished types of voters, as vetoes, passers or nulls, as well as some others, play a significant role in voting systems because they are either the most powerful or the least powerful voters in the game independently of the measure used to evaluate power. In this paper we are concerned with the design of voting systems with at least one type of these extreme voters and with few types of equivalent voters. With this purpose in mind we enumerate these special classes of games and find out that its number always follows a Fibonacci sequence with smooth polynomial variations. As a consequence we find several families of games with the same asymptotic exponential behavior except for a multiplicative factor which is the golden number or its square. From a more general point of view, our studies are related with the design of voting structures with a predetermined importance ranking., Peer Reviewed, Preprint

We consider a simple and altruistic multiagent system in which the agents are eager to perform a collective task but where their real engagement depends on the willingness to perform the task of other influential agents. We model this scenario by an influence game, a cooperative simple game in which a team (or coalition) of players succeeds if it is able to convince enough agents to participate in the task (to vote in favor of a decision). We take the linear threshold model as the influence model. We show first the expressiveness of influence games showing that they capture the class of simple games. Then we characterize the computational complexity of various problems on influence games, including measures (length and width), values (Shapley-Shubik and Banzhaf) and properties (of teams and players). Finally, we analyze those problems for some particular extremal cases, with respect to the propagation of influence, showing tighter complexity characterizations., Peer Reviewed, Postprint (author’s final draft)