Dpto. Estadística, Informática y Matemáticas - Estatistika, Informatika eta Matematika Saila [desde mayo 2018 / 2018ko maiatzetik]

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Open Access
Avatarians: playing with your friends' data
(ACM, 2012) Marzo Pérez, Asier; Ardaiz Villanueva, Óscar; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Gobierno de Navarra / Nafarroako Gobernua
This article describes a new game mechanic called Game Entity Social Mapping (GESM) based on using social networking data fetched from a remote site about the player and his contacts to create characters, items or scenarios. A preliminary evaluation consisting of applying this mechanic to three different games was conducted. A small number of users tested those games to measure the enjoyment and learning about their contacts information.
Open Access
Real elements and p-nilpotence of finite groups
(Aracne, 2016) Ballester Bolinches, Adolfo; Esteban Romero, Ramón; Ezquerro Marín, Luis Miguel; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2; Estadística, Informática y Matemáticas
Our first main result proves that every element of order 4 of a Sylow 2-subgroup S of a minimal non-2-nilpotent group G, is a real element of S. This allows to give a character-free proof of a theorem due to Isaacs and Navarro (see [9, Theorem B]). As an application, the authors show a common extension of the p-nilpotence criteria proved in [3] and [9].
Open Access
Nonlinear trapping stiffness of mid-air single-axis acoustic levitators
(American Institute of Physics, 2018) Fushimi, Tatsuki; Hill, Thomas L.; Marzo Pérez, Asier; Drinkwater, Bruce W.; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
We describe and experimentally explore a nonlinear stiffness model of the trapping of a solid particle in a single-axis acoustic levitator. In contrast to the commonly employed linear stiffness assumption, our nonlinear model accurately predicts the response of the system. Our nonlinear model approximates the acoustic field in the vicinity of the trap as a one-dimensional sinusoid and solves the resulting dynamics using numerical continuation. In particular, we predict a softening of stiffness with amplitude as well as period-doubling bifurcations, even for small excitation amplitudes of 2% of the wavelength. These nonlinear dynamic features are observed experimentally in a single-axis levitator operating at 40 kHz and trapping millimetre-scale expanded polystyrene spheres. Excellent agreement between the observed and predicted behaviour is obtained suggesting that this relatively simple model captures the relevant physical phenomena. This new model enables the dynamic instabilities of trapped particles to be accurately predicted, thereby benefiting contactless transportation and manipulation applications
Open Access
Decision making with horizontal cooperation and environmental criteria for transportation: optimization and simulation models for the vehicle routing problem and the facility location problem
(2018) Serrano Hernández, Adrián; Faulín Fajardo, Javier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Transportation is a major contributor to the development of the world economy and, at the same time, a major contributor to air pollution and global warming. Additionally, the unstoppable increase of competition as consequence of the globalization, as well as the increasingly service quality demanded by customers related to shorter times and lower costs, are forcing logistics companies to consider new managerial strategies. In this sense, horizontal cooperation among logistic companies is seen as a real alternative for gaining efficiency and sustainability. These agreements can be summarized as any arrangement between partners, tacit or not, which involves more than one company without vertical relationship between them, i.e., no supplier-customer relationship, based on trust and mutual commitment to identify and exploit win-win situations with the goal of sharing benefits (or risks) that would be higher (or lower) than each company would obtain if they acted completely independently. Therefore, in the first part of this thesis, several simulation models have been developed to track the evolution of a coalition in order to quantify horizontal cooperation impact in both economic and environmental sides considering the existence of trust-related issues. Additionally, as a great source of cooperation, a real application consisted on the location of a biorefinery is presented, developed, and discussed. On the other hand, environmental impacts of transportation should be measured and assessed for their integration in the existing optimization models. Thus, the second part of this thesis is devoted to the pricing through a contingent valuation survey of environmental impacts (externalities) and their internalization in the well-known Vehicle Routing Problem. In this sense, several optimization models are developed to assess the impact of the internalization of externalities on the routing decisions of logistics operations.
Open Access
Partial representations of orderings
(World Scientific, 2018) Bosi, Gianni; Estevan Muguerza, Asier; Zuanon, Magali; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
In the present paper a new concept of representability is introduced, which can be applied to not total and also to intransitive relations (semiorders in particular). This idea tries to represent the orderings in the simplest manner, avoiding any unnecessary information. For this purpose, the new concept of representability is developed by means of partial functions, so that other common definitions of representability (i.e. (Richter-Peleg) multi-utility, Scott-Suppes representability, … ) are now particular cases in which the partial functions are actually functions. The paper also presents a collection of examples and propositions showing the advantages of this kind of representations, particularly in the case of partial orders and semiorders, as well as some results showing the connections between distinct kinds of representations.
Open Access
Twofold binary image consensus for medical imaging meta-analysis
(Springer, 2018) López Molina, Carlos; Sánchez Ruiz de Gordoa, Javier; Zelaya Huerta, María Victoria; Baets, Bernard de; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
In the field of medical imaging, ground truth is often gathered from groups of experts, whose outputs are generally heterogeneous. This procedure raises questions on how to compare the results obtained by automatic algorithms to multiple ground truth items. Secondarily, it raises questions on the meaning of the divergences between experts. In this work, we focus on the case of immunohistochemistry image segmentation and analysis. We propose measures to quantify the divergence in groups of ground truth images, and we observe their behaviour. These measures are based upon fusion techniques for binary images, which is a common example of non-monotone data fusion process. Our measures can be used not only in this specific field of medical imagery, but also in any task related to meta-quality evaluation for image processing, e.g. ground truth validation or expert rating.
Open Access
Design exploration prior to blade multi-disciplinary optimisation
(IOP Publishing, 2018) Echeverría Durá, Fernando; Mallor Giménez, Fermín; San Miguel, Unai; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
The approach of designing blades as a multi-disciplinary, holistic optimisation implies significant challenges owing to the high complexity of the involved factors such as aerodynamics, elasticity, controller and loads. Moreover, the large number of design variables complicates the intuitive analysis of the relationship between the design variables and responses. This paper presents the design variable exploration prior to blade optimisation, which reveals certain design variable combinations that lead to undesirable dynamic load amplification. Statistical tools, such as multiple logistic regression and fast and frugal decision trees, are applied to identify the conditions causing the phenomenon and predict the possible appearance under new design variable combinations.
Open Access
Impact of successful treatment with directacting antiviral agents on health-related quality of life in chronic hepatitis C patients
(Public Library of Science, 2018) Juanbeltz Zurbano, Regina; Martínez Baz, Iván; San Miguel Elcano, Ramón; Goñi Esarte, Silvia; Cabasés Hita, Juan Manuel; Castilla Catalán, Jesús; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Economía; Ekonomia
Background. Direct-acting antivirals (DAA) have demonstrated high efficacy to achieve sustained virological response (SVR) in chronic hepatitis C patients. We aim to assess the change in healthrelated quality of life (HRQoL) among patients successfully treated, and to identify predictors of this variation. Methods. In a prospective observational study, patients with chronic hepatitis C who started DAA therapy between May 2016 and April 2017 completed the EQ-5D-5L questionnaire at baseline and 12 weeks after the end of therapy before knowing the virological result. Analysis included all patients with SVR. Results. Median baseline EQ-5D-5L scores of the 206 enrolled patients were 0.857 utility and 70.0 visual analogue scale (VAS). Following SVR, a reduction occurred in the proportion of patients with mobility problems (35% vs 24%, p = 0.012), pain/discomfort (60% vs 42%, p<0.001) and anxiety/depression (57% vs 44%, p = 0.012), with an increase in utility (+0.053, p<0.001) and VAS (+10, p<0.001). Score improvements were also observed in cirrhotic (+0.048 utility, p = 0.027; +15 VAS, p<0.001) and HIV co-infected patients (+0.039 utility, p = 0.036; +5 VAS, p = 0.002). In multivariate analyses, middle age (45±64 years) and baseline anxiety/depression were associated to greater improvement in utility after SVR, and moderate-advanced liver fibrosis and cirrhosis to greater increase in VAS score. Low baseline values were associated to greater improvements in utility value and VAS score. Conclusions The cure of chronic hepatitis C infection with DAA has a short term positive impact on HRQoL with improvement in mobility, pain/discomfort, anxiety/depression, utility value and VAS score. Patients with poor baseline HRQoL were the most beneficed.
Open Access
A study of different families of fusion functions for combining classifiers in the one-vs-one strategy
(Springer, 2018) Uriz Martín, Mikel Xabier; Paternain Dallo, Daniel; Jurío Munárriz, Aránzazu; Bustince Sola, Humberto; Galar Idoate, Mikel; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
In this work we study the usage of different families of fusion functions for combining classifiers in a multiple classifier system of One-vs-One (OVO) classifiers. OVO is a decomposition strategy used to deal with multi-class classification problems, where the original multi-class problem is divided into as many problems as pair of classes. In a multiple classifier system, classifiers coming from different paradigms such as support vector machines, rule induction algorithms or decision trees are combined. In the literature, several works have addressed the usage of classifier selection methods for these kinds of systems, where the best classifier for each pair of classes is selected. In this work, we look at the problem from a different perspective aiming at analyzing the behavior of different families of fusion functions to combine the classifiers. In fact, a multiple classifier system of OVO classifiers can be seen as a multi-expert decision making problem. In this context, for the fusion functions depending on weights or fuzzy measures, we propose to obtain these parameters from data. Backed-up by a thorough experimental analysis we show that the fusion function to be considered is a key factor in the system. Moreover, those based on weights or fuzzy measures can allow one to better model the aggregation problem.
Open Access
The interval-valued Choquet integral based on admissible permutations
(IEEE, 2018) Paternain Dallo, Daniel; Miguel Turullols, Laura de; Ochoa Lezaun, Gustavo; Lizasoain Iriso, María Inmaculada; Mesiar, Radko; Bustince Sola, Humberto; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Estadística, Informática y Matemáticas; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Aggregation or fusion of interval data is not a trivial task, since the necessity of arranging data arises in many aggregation functions, such as OWA operators or the Choquet integral. Some arranging procedures have been given to solve this problem, but they need certain parameters to be set. In order to solve this problem, in this work we propose the concept of an admissible permutation of intervals. Based on this concept, which avoids any parameter selection, we propose a new approach for the interval-valued Choquet integral that takes into account every possible permutation fitting to the considered ordinal structure of data. Finally, a consensus among all the permutations is constructed.
Open Access
Dynamics in the charged restricted circular three-body problem
(Springer US, 2018) Palacián Subiela, Jesús Francisco; Vidal Díaz, Claudio; Vidarte, Jhon; Yanguas Sayas, Patricia; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
The existence and stability of periodic solutions for different types of perturbations associated to the Charged Restricted Circular Three Body Problem (shortly, CHRCTBP) is tackled using reduction and averaging theories as well as the technique of continuation of Poincaré for the study of symmetric periodic solutions. The determination of KAM 2-tori encasing some of the linearly stable periodic solutions is proved. Finally, we analyze the occurrence of Hamiltonian-Hopf bifurcations associated to some equilibrium points of the CHRCTBP.
Open Access
Características y métodos estadísticos empleados en los artículos originales publicados en las revistas de salud pública en España
(Gobierno de Navarra, 2018) Martínez Baz, Iván; Delfrade Osinaga, J.; Etxeberria Andueza, Jaione; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Background. To describe the characteristics and statistical methods used in the original articles published in Gaceta Sanitaria, Revista Española de Salud Pública y Anales del Sistema Sanitario de Navarra, the Spanish public health journals in Spain indexed in the 2016 JRC. Methods. All articles published in these journals in 2007, 2012 and 2017 were reviewed. For each article, general aspects (year, journal, language, area) and statistical characteristics (design, purpose, method and software) were recorded. Results. A total of 310 articles were reviewed, 73% of them were cross-sectional studies. Evaluation and health services (24%) and chronic diseases were the most frequent areas. During the 2007-2017 period there was an increase in both the number of works written in English (4 vs 20%, p<0.001) and by women as the main (46 vs 62%, p=0.028) or senior authors (27 vs 36%, p=0.029). Significant changes concerning type of analysis were not detected (p=0.933). Conclusions. The characteristics and statistical methods used in scientific publications have not been modified in recent years. However, publications written in English have increased and women are playing a more relevant role in authorship.
Open Access
Managing transportation externalities in the Pyrenees region: measuring the willingness-to-pay for road freight noise reduction using an experimental auction mechanism
(Elsevier, 2018) Denant-Boemont, Laurent; Faulín Fajardo, Javier; Hammiche, Sabrina; Serrano Hernández, Adrián; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Estadística, Informática y Matemáticas
The estimation of the noise impact caused by road freight transportation is critical to have acknowledgment of the ambiance pollution caused by road traffic crossing geographical areas containing important natural resources. Thus, our work proposes a within-subject survey where a Contingent Valuation Method (CVM) is combined with a laboratory economic experimental auction. Our study objective is to measure the willingness-to-pay (WTP) for reducing traffic noise nuisances due to freight transportation in the region of Navarre, Spain. A special focus is made regarding the measurement of the hypothetical bias, when a comparison is done between hypothetical WTP, coming from the CVM study, with real-incentivized one, as the outcome of the economic experiment. Additionally, statistical analyses are conducted in order to find explanation factors for these outcomes. Results suggest a strong evidence for an upward hypothetical bias (from 50% to 160%) indicating the income, the educational level, the gender, and the age as the main factors which explain that bias.
Open Access
Gongora-ko (Nafarroa) Jauregizaharra jauregiaren datazio dendrokronologikoa
(Sociedad de Ciencias Aranzadi, 2018) Lizeaga Rica, Joseba Sabin; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
En este trabajo se presenta la datación dendrocronológica del palacio Jauregizaharra de Gongora (Navarra). Desde el aspecto dendrocronológico se han construido 3 cronologías de referencia, y, desde el punto de vista de la historia de edificios de linajes aristocráticos, se presenta la datación de las fases del palacio. Desde el lado dendrocronológico se han analizado un total de 242 maderas de roble pubescente, quejigo, pino albar y olmo. Se han comparado con cronologías absolutas de la zona. Esta comparación ha dado dataciones de derribo del árbol del siglo XV hasta el XIX. Inicialmente constaba de una torre de base cuadrada. Alrededor de la torre se fueron construyendo diversos edificios hasta crear un primer patio a finales del siglo XV. El siglo XVI se construyó un segundo patio más amplio. Tomando en consideración las dataciones de corte de los árboles se puede decir que la mayor parte del palacio se construyó entre los años 1445 y 1510.
Open Access
Image feature extraction using OD-monotone functions
(Springer, 2018) Marco Detchart, Cedric; López Molina, Carlos; Fernández Fernández, Francisco Javier; Pagola Barrio, Miguel; Bustince Sola, Humberto; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Estadística, Informática y Matemáticas
Edge detection is a basic technique used as a preliminary step for, e.g., object extraction and recognition in image processing. Many of the methods for edge detection can be fit in the breakdown structure by Bezdek, in which one of the key parts is feature extraction. This work presents a method to extract edge features from a grayscale image using the so-called ordered directionally monotone functions. For this purpose we introduce some concepts about directional monotonicity and present two construction methods for feature extraction operators. The proposed technique is competitive with the existing methods in the literature. Furthermore, if we combine the features obtained by different methods using penalty functions, the results are equal or better results than stateof-the-art methods.
Open Access
Detecting change-points in the time series of surfaces occupied by pre-defined NDVI categories in continental Spain from 1981 to 2015
(Springer, 2018) Militino, Ana F.; Ugarte Martínez, María Dolores; Pérez Goya, Unai; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2
The free access to satellite images since more than 40 years ago has provoked a rapid increase of multitemporal derived information of remote sensing data that should be summarized and analyzed for future inferences. In particular, the study of trends and trend changes is of crucial interest in many studies of phenology, climatology, agriculture, hydrology, geology or many other environmental disciplines. Overall, the normalized dierence vegetation index (NDVI), as a satellite derived variable, plays a crucial role because of its usefulness for vegetation and landscape characterization, land use and land cover mapping, environmental monitoring, climate change or crop prediction models. Since the eighties, it can be retrieved all over the world from dierent satellites. In this work we propose to analyze its temporal evolution, looking for breakpoints or change-points in trends of the surfaces occupied by four NDVI classications made in Spain from 1981 to 2015. The results show a decrease of bare soils and semi-bare soils starting in the middle nineties or before, and a slight increase of middle-vegetation and high-vegetation soils starting in 1990 and 2000 respectively.
Open Access
Dynamic mean absolute error as new measure for assessing forecasting errors
(Elsevier, 2018) Gastón Romeo, Martín; Frías Paredes, Laura; Mallor Giménez, Fermín; León, Teresa; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
Accurate wind power forecast is essential for grid integration, system planning, and electricity trading in certain electricity markets. Therefore, analyzing prediction errors is a critical task that allows a comparison of prediction models and the selection of the most suitable model. In this work, the temporal error and absolute magnitude error are simultaneously considered to assess the forecast error. The trade-off between both types of errors is computed, analyzed, and interpreted. Moreover, a new index, the dynamic mean absolute error, DMAE, is defined to measure the prediction accuracy. This index accounts for both error components: temporal and absolute. Real cases of wind energy forecasting are used to illustrate the use of the new DMAE index and show the advantages of this new index over other error indices.
Open Access
Outcomes and features of the inspection of receiver tubes (ITR) system for improved O&M in parabolic trough plants
(American Institute of Physics, 2018) Olano, Xabier; García de Jalón, Alberto; Pérez, David; García Barberena, Javier; López, Javier; Gastón Romeo, Martín; Estadística e Investigación Operativa; Estatistika eta Ikerketa Operatiboa
Concentrated solar power (CSP) plants based on parabolic trough (PT), after several years since their commissioning, demand new operation and maintenance (O&M) developments. Particularly, the receiver tube´s potential degradation over time is a real challenge. In this paper, the current version of the ITR System's last developments and advanced features are presented together with the main outcomes provided by the system for a real, complete solar field inspection in a commercial PT power plant. Exemplarily, this commercial ITR inspection showed that 0.8% of the tubes were underperforming and thus classified as outliers, while the average relative power of the tubes from the solar field resulted in about 97% of the ideal tubes' power. This paper shows that, thanks to the ITR Inspection System, plant operators can more easily develop and adopt improved O&M strategies, such as corrective and preventive actions in the solar field and even predictive actions in case of periodic inspections.
Open Access
Acoustic lock: position and orientation trapping of non-spherical sub-wavelength particles in mid-air using a single-axis acoustic levitator
(American Institute of Physics, 2018) Cox, L; Croxford, A; Drinkwater, Bruce W.; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
We demonstrate acoustic trapping in both position and orientation of a non-spherical particle of sub-wavelength size in mid-air. To do so, we multiplex in time a pseudo-one-dimensional vertical standing wave and a twin-trap; the vertical standing wave provides converging forces that trap in position, whereas the twin-trap applies a stabilising torque that locks the orientation. The device operates at 40 kHz, and the employed multiplexing ratio of the 2 acoustic fields is 100:50 (standing:twin) periods. This ratio can be changed to provide tunability of the relative trapping strength and converging torque. The torsional spring stiffness of the trap is measured through simulations and experiments with good agreement. Cubes from k/5.56 (1.5 mm) to k/2.5 (3.4 mm) side length were stably locked. We also apply this technique to lock different non-spherical particles in midair: cubes, pyramids, cylinders, and insects such as flies and crickets. This technique adds significant functionality to mid-air acoustic levitation and will enable applications in micro-scale manufacturing as well as containment of specimens for examination and 3D-scanning.
Open Access
Geometrical aggregation of finite fuzzy sets
(Elsevier, 2018) Campión Arrastia, María Jesús; García Catalán, Olga Raquel; Induráin Eraso, Esteban; Lizasoain Iriso, María Inmaculada; Raventós Pujol, Armajac; Valero, Óscar; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2; Institute for Advanced Research in Business and Economics - INARBE; Estadística, Informática y Matemáticas
A fuzzy set on a finite universe can be interpreted as a vector in a unit cube. This gives rise to a huge variety of approaches in order to aggregate finite fuzzy sets or to modify a given one. We analyze several geometrical methods and discuss possible applications in a multidisciplinary setting.