José M. Amigó (University Miguel Hernández of Elche), Guillem Duran, (Fragile Technologies, Murcia), Angel Giménez (University Miguel Hernández of Elche), Oscar Martínez-Bonastre (University Miguel Hernández of Elche) and José Valero (University Miguel Hernández of Elche).
Abstract: Adaptive management of traffic congestion in the Internet is a complex problem that can gain useful insights from a dynamical approach. In this paper we propose and analyze a one-dimensional, discrete-time nonlinear model for Internet congestion control at the routers. Specifically, the states correspond to the average queue sizes of the incoming data packets and the dynamical core consists of a monotone or unimodal mapping with a unique fixed point. This model generalizes a previous one in that additional control parameters are introduced via the data packet drop probability with the objective of enhancing stability. To make the analysis more challenging, the original model was shown to exhibit the usual features of low-dimensional chaos with respect to several system and control parameters, e.g., positive Lyapunov exponents and Feigenbaum-like bifurcation diagrams. We concentrate first on the theoretical aspects that may promote the unique stationary state of the system to a global attractor, which in our case amounts to global stability. In a second step, those theoretical results are translated into stability domains for robust setting of the new control parameters in practical applications. Numerical simulations confirm that the new parameters make it possible to extend the stability domains, in comparison with previous results. Therefore, the present work may lead to an adaptive congestion control algorithm with a more stable performance than other algorithms currently in use.
Keywords. Congestion control in the Internet ; Adaptive queue management ;Random early detection ; Discrete-time dynamical systems; Global stability; Robust setting of control parameters .
Nuria Ramón (University Miguel Hernández of Elche), José L. Ruiz(University Miguel Hernández of Elche) and Inmaculada Sirvent (University Miguel Hernández of Elche).
Abstract.In benchmarking, organizations look outward to examine others’ performance in their industry or sector. Often, they can learn from the best practices of some of them and improve. In order to develop this idea within the framework of Data Envelopment Analysis (DEA), this paper extends the common benchmarking framework proposed in Ruiz and Sirvent (2016) to an approach based on the benchmarking of decision making units (DMUs) against several reference sets. We refer to this approach as cross-benchmarking. First, we design a procedure aimed at making a selection of reference sets (as defined in DEA), which establish the common framework for the benchmarking. Next, benchmarking models are formulated which allow us to set the closest targets relative to the reference sets selected. The availability of a wider spectrum of targets may offer managers the possibility of choosing among alternative ways for improvements,taking into account what can be learned from the best practices of different peer groups. Thus, crossbenchmarking is a flexible tool that can support a process of future planning while considering different managerial implications.
Keywords. Performance evaluation; Data envelopment analysis; Benchmarking; Target setting.
M. G. Fiestras-Janeiro (University of Vigo), I. García-Jurado (University of A Coruña), A. Meca (University Miguel Hernández of Elche) and M. A. Mosquera(University of Vigo).
Abstract. We introduce a new model involving TU-games and exogenous structures. Specifically, we consider that each player in a population can choose an element in a strategy set and that, for every possible strategy profile, a TU-game is associated with the population. This is what we call a TU-game with strategies. We propose and characterize the maxmin procedure to map every game with strategies to a TU-game. We also study whether or not the relevant properties of TU-games are transmitted by applying the maxmin procedure. Finally, we examine two relevant classes of TU-games with strategies: airport and simple games with strategies
Keywords. Game theory; Cooperative games; Maxmin procedure; Strategies; Airport games; Simple games.
Guillem Duran (University Miguel Hernández of Elche), José Valero (University Miguel Hernández of Elche), José M. Amigó (University Miguel Hernández of Elche), Ángel Giménez (University Miguel Hernández of Elche) and Óscar Martínez- Bonastre (University Miguel Hernández of Elche).
Abstract. The bifurcation and chaotic behavior of Two may cause heavy oscillation of average queue length at routers and induce network instability. In the context, congestion control in the Internet is a challenging problem of key importance. This work presents a new discrete dynamical model of Random Early Detection (RED) using beta distribution for controlling bifurcations and chaos in the internet congestion control. The numerical analysis and the simulation experiments show that this new Active Queue Management (AQM) model can obtain the stable average queue length to the desired fix point. The model programmed with Python and Mathematica incorporates new parameters that make it possible to stabilize oscillations of averaged router queue length and to be close to stationary state.
Keywords. Congestion control; Active Queue Management (AQM); Internet; Discrete dynamical systems.
María Dolores Esteban(University Miguel Hernández of Elche), María José Lombardía (University of A Coruña), Esther López-Vizcaíno ( Galician Institute of Statistics), Domingo Morales (University Miguel Hernández of Elche) and Agustín Pérez (University Miguel Hernández of Elche).
Abstract. This paper introduces area-level compositional mixed models by applying transformations to a multivariate Fay–Herriot model. Small area estimators of the proportions of the categories of a classification variable are derived from the new model, and the corresponding mean squared errors are estimated by parametric bootstrap. Several simulation experiments designed to analyse the behaviour of the introduced estimators are carried out. An application to real data from the Spanish Labour Force Survey of Galicia (north-west of Spain), in the first quarter of 2017, is given. The target is the estimation of domain proportions of people in the four categories of the variable labour status: under 16 years, employed, unemployed and inactive.
Keywords. Labour Force Survey; Area-level models; Compositional data; Bootstrap; Labour status,
Jenny Morales (Universidad Autónoma de Chile), Cristian Rusu (Universidad Católica de Valparaíso), Federico Botella (University Miguel Hernández of Elche) and Daniela Quiñones (Universidad Católica de Valparaíso)
Abstract. Programmers use various software development artifacts in their work, such as programming environments, design documents, and programming codes. These software artifacts can be studied and improved based on usability and User eXperience (UX) factors. In this paper, we consider programmers to be a specic case of users and analyze different elements that inuence their experience in this specic context. We conducted a systematic literature review of papers published over the last ten years related to 1) the denition of the Programmer eXperience (PX); 2) the PX, UX, and usability factors regarding the programming environments, design documents, and programming codes; and 3) sets of heuristics to evaluate the software development artifacts mentioned before.We analyzed 73 articles, and the results obtained show that: 1) the important elements that inuence the PX are the motivation of programmers and the choice of tools they use in their work, such as programming environments; 2) most of the identied studies (59%) aimed to evaluate the inuence of the PX, UX, and usability on programming environments; 3) the majority of the studies (70%) used methods such as usability tests and/or heuristic evaluation methods; and 4) four sets of heuristics are used to evaluate software development artifacts in relation to programming environments, programming languages, and application programming interfaces. The results suggest that further research in this area is necessary to better understand and evaluate the concept of the PX.
Keywords. Heuristic evaluation; Programmer eXperience; systematic literature review; User eXperience; usability.