Artículos de revista ISC - ISC aldizkari artikuluak

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Open Access
Advancing ASL kidney image registration: a tailored pipeline with VoxelMorph
(Springer, 2025-01-31) Oyarzun Domeño, Anne; Cia Alonso, Izaskun; Echeverría Chasco, Rebeca; Fernández Seara, María A.; Martín Moreno, Paloma L.; García Fernández, Nuria; Bastarrika, Gorka; Navallas Irujo, Javier; Villanueva Larre, Arantxa; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
In clinical renal assessment, image registration plays a pivotal role, as patient movement during data acquisition can significantly impede image post-processing and the accurate estimation of hemodynamic parameters. This study introduces a deep learning-based image registration framework specifically for arterial spin labeling (ASL) imaging. ASL is a magnetic resonance imaging technique that modifies the longitudinal magnetization of blood perfusing the kidney using a series of radiofrequency pulses combined with slice-selective gradients. After tagging the arterial blood, label images are captured following a delay, allowing the tagged blood bolus to enter the renal tissue, while control images are acquired without tagging the arterial spins. Given that perfusion maps are generated at the pixel level by subtracting control images from label images and considering the relatively small signal intensity difference, precise alignment of these images is crucial to minimize motion artefacts and prevent significant errors in perfusion calculations. Moreover, due to the extended ASL acquisition times and the anatomical location of the kidneys, renal images are often susceptible to pulsation, peristalsis, and breathing motion. These motion-induced noises and other instabilities can adversely affect ASL imaging outcomes, making image registration essential. However, research on renal MRI registration, particularly with respect to learning-based techniques, remains limited, with even less focus on renal ASL. Our study proposes a learning-based image registration approach that builds upon VoxelMorph and introduces groupwise inference as a key enhancement. The dataset includes 2448 images of transplanted kidneys (TK) and 2456 images of healthy kidneys (HK). We compared the automatic image registration results with the widely recognized optimization method Elastix. The model’s performance was evaluated using the mean structural similarity index (MSSIM), normalized correlation coefficient (NCC), temporal signal-tonoise ratio (TSNR) of the samples, and the mean cortical signal (CSIM) in perfusion-weighted images, thereby extending the evaluation beyond traditional similarity-based metrics. Our method achieved superior image registration performance, with peak NCC (0.987 ± 0.006) and MSSIM (0.869 ± 0.048) values in the kidney region, significantly surpassing Elastix and the unregistered series (p\ 0.05) on TK and HK datasets. Regularization analysis showed that higher k values (1, 2) produced smoother deformation fields, while moderate k values (0.5, 0.9) balanced smoothness and detail, maintaining low non-positive Jacobian percentages (\1%) comparable to Elastix. Additionally, our method improved CSIM by 14.3% (2.304 ± 1.167) and TSNR by 13.1% (3.888 ± 2.170) in TK, and achieved up to 13.2% (CSIM) and 29.8% (TSNR) enhancements in HK, demonstrating robustness and improved signal quality across datasets and acquisition techniques.
Open Access
Photonic chip breath analyzer
(SpringerOpen, 2025-06-03) Gallego Martínez, Elieser Ernesto; Matías Maestro, Ignacio; Ruiz Zamarreño, Carlos; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This work introduces a novel single-package optical sensing device for multiple gas sensing, which is suitable for breath analysis applications. It is fabricated on a coverslip substrate via a sputtering technique and uses a planar waveguide configuration with lateral incidence of light. It features three sequentially ordered strips of different materials, which serve to increase the multivariate nature of the response of the device to different gases. For the proof-of-concept, the selected materials are indium tin oxide (ITO), tin oxide (SnO2), and chromium oxide III (Cr2O3), while the selected gases are nitric oxide (NO), acetylene (C2H2), and ammonia (NH3). The sensing mechanism is based on the hyperbolic mode resonance (HMR) effect, with the first-order resonance obtained for each strip located in the near infrared region. The multivariate response of the resonances and the correlation with the concentration of each gas allow training a machine learning (ML) model based on a nonlinear autoregressive neural network, enabling the accurate prediction of the concentration of each gas. The obtained limit of detection for all the gases was in the order of a few parts per billion. This innovative approach coined as the multivariate optical resonances spectroscopy demonstrates the potential of HMR-based optical sensors in combination with ML techniques for ultra-sensitive multi-gas detection applications using a single device.
Open Access
Formalize clinical processes into electronic health information systems: modelling a screening service for diabetic retinopathy
(Elsevier, 2015-06-14) Eguzkitza Diego, Aitor; Trigo Vilaseca, Jesús Daniel; Martínez de Espronceda Cámara, Miguel; Serrano Arriezu, Luis Javier; Andonegui Navarro, José; Ciencias de la Salud; Osasun Zientziak; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Most healthcare services use information and communication technologies to reduce and redistribute the workload associated with follow-up of chronic conditions. However, the lack of normalization of the information handled in and exchanged between such services hinders the scalability and extendibility. The use of medical standards for modelling and exchanging information, especially dual-model based approaches, can enhance the features of screening services. Hence, the approach of this paper is twofold. First, this article presents a generic methodology to model patient-centered clinical processes. Second, a proof of concept of the proposed methodology was conducted within the diabetic retinopathy (DR) screening service of the Health Service of Navarre (Spain) in compliance with a specific dual-model norm (openEHR). As a result, a set of elements required for deploying a model-driven DR screening service has been established, namely: clinical concepts, archetypes, termsets, templates, guideline definition rules, and user interface definitions. This model fosters reusability, because those elements are available to be downloaded and integrated in any healthcare service, and interoperability, since from then on such services can share information seamlessly.
Open Access
High fidelity CFD models comparison to potential flow method in the simulation of full scale floating platform under free decay tests
(Elsevier, 2025-05-01) Gil Liberal, Miguel; Armañanzas Goñi, Javier; Torres Salcedo, Alexia; Fuertes Bonel, Juan Pablo; Campaña, Guillén; Méndez López, Beatriz; León Iriarte, Javier; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
The use of simulation models based on potential flow is widespread in the wind industry for the simulation of floating wind turbines. However, these analytical models have shortcomings in correctly representing the behavior of Floating Offshore Wind Turbines (FOWTs) under extreme wind and wave conditions. High fidelity Computational Fluid Dynamics (CFD) simulations aim to develop models where the fluid-structure interaction is more accurately modeled, allowing to correctly predict the behavior of wind turbines and thus to redesign structural components and save costs. In this paper, two different CFD simulation models are developed and compared, including different turbulence models (Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES)), numerical methodologies (Navier-Stokes and Lattice-Boltzmann method) and mooring models (Quasi-Static and Dynamic). Different free decay Load Cases (LC) are performed in XFlow and OpenFOAM, and the damping ratio and natural period of the system are analyzed with different mooring arrangements (Multi-Point Mooring (MPM) and Single-Point Mooring (SPM)), comparing all results with respect to a potential flow model (HydroDyn). A maximum error of 3.3 % in natural period and 1.6 % error in damping factor is obtained, small enough to validate the results of CFD models. Vorticity is also analyzed to understand the differences between both CFD models. Finally, the stress of the mooring lines is computed, which allows validating the mooring system model implemented in XFlow by means of external functions.
Open Access
EMG filling analysis, a new method for the assessment of recruitment of motor units with needle EMG
(Elsevier, 2025-02-20) Mariscal Aguilar, Cristina; Navallas Irujo, Javier; Malanda Trigueros, Armando; Recalde Villamayor, Silvia; Rodríguez Falces, Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Objectives: The progression of recruitment of motor unit potentials (MUPs) during increasing voluntary contraction can provide important information about the motor units (MUs) innervating a muscle. Here, we described a method to quantitate the recruitment level of the intramuscular electromyographic (iEMG) signal during an increasing force level. Methods: Concentric needle EMG signals were recorded from the tibialis anterior of healthy subjects as force was gradually increased from 0 to maximum force. The iEMG filling process was analyzed by measuring the EMG filling factor (FF), calculated from the mean rectified iEMG and the root mean square iEMG. Results: (1) The iEMG activity at low contraction forces was “discrete” (FF<0.3) for all participants. (2) The iEMG activity at maximal effort was “full” (FF>0.5) for 83 % of the participants, whereas it was “incompletely-reduced” (0.3
Open Access
Effects of time-restricted eating and resistance training on skeletal muscle tissue quantity, quality and function in postmenopausal women with overweight or obesity: a study protocol
(Elsevier, 2024-12-30) Alfaro-Magallanes, Víctor Manuel; Medrano Echeverría, María; Echarte Medina, Jon; Osés Recalde, Maddi; Izquierdo Rodríguez, Claudia; Concepción Álvarez, Mara de la Caridad; Galbete Jiménez, Arkaitz; Idoate, Fernando; Zugasti Murillo, Ana; Petrina Jáuregui, María Estrella; Goñi Gironés, María Elena; Ribelles, María Jesús; Amasene, María; Arenaza Etxeberría, Lide; Tejada Garrido, Clara Isabel; Elejalde, E.; Azcárate Jiménez, Unai Xabier; Ruiz Sarrias, Oskitz; Sayar-Beristain, Onintza; García-Ramos, Amador; Martínez Labari, Cristina; Armendáriz Brugos, Cristina; Villanueva Larre, Arantxa; Ruiz Ruiz, Jonatan; Cabeza Laguna, Rafael; Labayen Goñi, Idoia; Ciencias de la Salud; Osasun Zientziak; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
Background & aims: time-restricted eating (TRE) shows promise for weight loss and improving menopauserelated body composition and cardiometabolic health, but its effects on skeletal muscle tissue (SMT) in postmenopausal women are unknown. This study investigates the effects of three weight loss interventions over 12 weeks on SMT quantity, quality, function, and cardiometabolic health in postmenopausal women with overweight/obesity, with effects persistence evaluated at a 12-month follow-up. Methods and results: in this randomized controlled trial, 78 postmenopausal women (50–65 years; BMI 25–40 kg/m2; sedentary lifestyle; eating window ≥12 h/day; no severe metabolic impairments) will be recruited. Participants will be randomly assigned to one of three groups for 12 weeks: TRE, TRE + resistance training, or CR + resistance training. The TRE groups will reduce their eating window to 8 h and receive nutritional advice to adhere to a Mediterranean diet. The CR group will follow a personalized hypocaloric diet (− 500 kcal/day). Resistance training groups will perform supervised resistance training 3 times/week. Primary Outcome: Change in SMT quantity measured by MRI at baseline and after 12 weeks. Secondary Outcomes: intermuscular adipose tissue (IMAT), strength, power, body weight and composition, and cardiometabolic risk factors. Conclusion: this study will illustrate the effects of TRE and TRE combined with resistance exercise compared with the currently recommended obesity-lifestyle treatment on SMT quantity, quality, function, and cardiometabolic markers. The results will offer insights into dietary strategies to combat obesity and metabolic diseases without increasing sarcopenia risk in postmenopausal women, a sparsely studied and particularly affected population.
Open Access
Reducción del miedo al entorno sanitario en niños usando espacios simulados: un ensayo controlado aleatorizado
(Elsevier, 2024-04-10) Soto Ruiz, María Nelia; Escalada Hernández, Paula; García Vivar, Cristina; Ferraz Torres, Marta; Saralegui Gainza, Amaia; San Martín Rodríguez, Leticia; Ciencias de la Salud; Osasun Zientziak; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
Objetivo: El objetivo de este estudio fue evaluar la efectividad de una intervención que implicó interacciones dentro de un espacio de atención sanitaria simulado para reducir el miedo al entorno sanitario entre los niños de educación infantil. Métodos: Se llevó a cabo un estudio experimental en el que participaron a 86 niños, divididos en los grupos intervención (GI) y control (GC), con medidas antes y después de la intervención. Esta última, denominada Programa Health-Friendly, consistió en enseñar a los niños diversos escenarios que simularon diferentes contextos sanitarios, para que pudieran interactuar en ellos, experimentar con los materiales y realizar preguntas. El miedo al entorno sanitario fue evaluado mediante la versión en español revisada de Child Medical Fear Scale (CMFS-R), que proporciona una puntuación al nivel de miedo al entorno sanitario que fluctúa de 0 a 34 puntos. Los niveles de miedo al entorno sanitario antes y después de la prueba en los grupos intervención y control fueron comparados mediante la prueba t de Student. Resultados: Los niños del GI experimentaron una reducción significativa del miedo de 3,21 puntos (desviación estándar [DE]: 6,50) en comparación con los niños del GC. Dicha reducción del miedo se reflejó en las cuatro dimensiones de la escala: miedos intrapersonales, miedos procedimentales, miedos ambientales y miedos interpersonales. Conclusión: El Programa Health-Friendly proporciona una intervención innovadora para reducir el miedo al entorno sanitario entre los niños, basada en información, estrategias de confrontación y escenarios de simulación. Este estudio sugiere el beneficio potencial de incorporar intervenciones educativas en las escuelas, en colaboración con los centros universitarios y los centros de simulación de la atención sanitaria.
Open Access
A reliability-extended simheuristics for the sustainable vehicle routing problem with stochastic travel times and demands
(Springer, 2025-04-01) Abdullahi, Hassana; Reyes-Rubiano, Lorena Silvana; Ouelhadj, Djamila; Faulín Fajardo, Javier; Juan, Ángel A.; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Real-life transport operations are often subject to uncertainties in travel time or customers'demands. Additionally, these uncertainties greatly impact the economic, environmental, and social costs of vehicle routing plans. Thus, analysing the sustainability costs of transportation activities and reliability in the presence of uncertainties is essential for decision makers. Accordingly, this paper addresses the Sustainable Vehicle Routing Problem with Stochastic Travel times and Demands. This paper proposes a novel weighted stochastic recourse model that models travel time and demand uncertainties. To solve this challenging problem, we propose an extended simheuristic that integrates reliability analysis to evaluate the reliability of the generated solutions in the presence of uncertainties. An extensive set of computational experiments is carried out to illustrate the potential of the proposed approach and analyse the influence of stochastic components on the different sustainability dimensions.
Open Access
Highly efficient focusing of terahertz waves with an ultrathin superoscillatory metalens: experimental demonstration
(Wiley, 2021-05-06) Legaria Lerga, Santiago; Teniente Vallinas, Jorge; Kuznetsov, Sergei A.; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Institute of Smart Cities - ISC
The performance of an ultrathin (thickness < 0.04λ 0) metasurface superoscillatory lens (metaSOL) is experimentally demonstrated in the terahertz (THz) range. The metaSOL is designed using two different hexagonal unit cells to improve the efficiency and properties of the conventional transparent–opaque zoning approach. The focusing metastructure produces, at a frequency f exp = 295 GHz, a sharp focal spot 8.9λ exp away from its output surface with a transversal resolution of 0.52λ exp (≈25% below the resolution limit imposed by diffraction), a power enhancement of 18.2 dB, and very low side lobe level (−13 dB). Resolution below the diffraction limit is demonstrated in a broad fractional operation bandwidth of 18%. The focusing capabilities of the proposed metaSOL show its potential use in a range of applications such as THz imaging, microscopy, and communications.
Embargo
Compensation strategy to minimize over-cut effects in robotic belt grinding with passive-compliant tools
(Elsevier, 2025-03-19) Torres Izu, Ramón; Iriarte Goñi, Xabier; Mata Cantón, Sara; Aginaga García, Jokin; Barrenetxea Azpeitia, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
At the beginning of the robotic belt grinding path, passive-compliant tools can generate an over-cut effect. The transient state from the first contact point between tool and workpiece to the grinding steady state can generate an excess of material removal at the workpiece border. If successive grinding passes are made, this effect will accumulate, increasing the shape deviation at the workpiece border. Therefore, the purpose of this research is to analyze this phenomenon and develop an easy-to-implement compensation strategy to avoid removing an excess of material at the beginning of grinding paths. Specifically, a geometric model of the contact has been developed that, together with the material removal model, allows to reproduce the cut-in effect for a robot-operated passive-compliant tool case. In turn, the compensation strategy that has been designed, avoids removing an excessive amount of material by means of a cut-in path that adjusts the feed velocity to the instantaneous contact force. This path is based on the tool geometry and grinding process parameters. In order to validate the proposed strategy, several experiments have been performed for different process conditions. Results show how the proposed solution significantly reduces the over-cut effect providing a homogeneous material removal since the beginning of the grinding.
Open Access
Data stream clustering: introducing recursively extendable aggregation functions for incremental cluster fusion processes
(IEEE, 2025-03-07) Urío Larrea, Asier; Camargo, Heloisa A.; Lucca, Giancarlo; Asmus, Tiago da Cruz; Marco Detchart, Cedric; Schick, L.; López Molina, Carlos; Andreu-Pérez, Javier; Bustince Sola, Humberto; Dimuro, Graçaliz Pereira; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
In data stream (DS) learning, the system has to extract knowledge from data generated continuously, usually at high speed and in large volumes, making it impossible to store the entire set of data to be processed in batch mode. Hence, machine learning models must be built incrementally by processing the incoming examples, as data arrive, while updating the model to be compatible with the current data. In fuzzy DS clustering, the model can either absorb incoming data into existing clusters or initiate a new cluster. As the volume of data increases, there is a possibility that the clusters will overlap to the point where it is convenient to merge two or more clusters into one. Then, a cluster comparison measure (CM) should be applied, to decide whether such clusters should be combined, also in an incremental manner. This defines an incremental fusion process based on aggregation functions that can aggregate the incoming inputs without storing all the previous inputs. The objective of this article is to solve the fuzzy DS clustering problem of incrementally comparing fuzzy clusters on a formal basis. First, we formalize and operationalize incremental fusion processes of fuzzy clusters by introducing recursively extendable (RE) aggregation functions, studying construction methods and different classes of such functions. Second, we propose two approaches to compare clusters: 1) similarity and 2) overlapping between clusters, based on RE aggregation functions. Finally, we analyze the effect of those incremental CMs on the online and offline phases of the well-known fuzzy clustering algorithm d-FuzzStream, showing that our new approach outperforms the original algorithm and presents better or comparable performance to other state-of-the-art DS clustering algorithms found in the literature.
Open Access
Lossy mode resonances generated in planar configuration for two-parameter sensing
(IEEE, 2021-04-29) Fuentes Lorenzo, Omar; Corres Sanz, Jesús María; Domínguez Rodríguez, Ismel; Del Villar, Ignacio; Matías Maestro, Ignacio; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
This work shows a new sensor structure for simultaneous measurement of two parameters, temperature and refractive index. The optical configuration consists of incidence of light on the edge of a soda-lime coverslip fully coated with a CuO thin film and partially coated with a PDMS thick layer. This planar configuration permitted to generate two separated lossy mode resonances (LMRs): one centered at 600 nm and the other at 1000 nm. The second resonance is induced by the PDMS layer and it can be used to measure the temperature due to its high thermo-optic coefficient (the sensitivity is -1.75 nm/°C in the temperature range from 20 to 40 °C), whereas the first resonance is used for sensing refractive index with sensitivity of 1460 nm/RIU in the refractive index range from 1.3328 and 1.37. Finally, a calibration test was carried out using a calibrated oil series with refractive index ranging from 1.33 to 1.36. This work demonstrates the possibility of generating multiples resonances in a single structure as simple as a coverslip, which can be used as a multi-parameter interchangeable sensor, especially suitable for biological applications or the detection of heavy metals in water.
Open Access
Análisis ergonómico de la viticultura moderna
(Asociación Navarra de Ergonomía (ANER), 2023) González Moreno, Miguel Ángel; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
Se realiza la identificación de los principales riesgos ergonómicos en el sector vitícola a través del análisis de las diferentes labores realizadas durante una campaña completa, desde la poda invernal hasta la vendimia de la cosecha.
Open Access
Riesgos ergonómicos en las ITEAF
(Asociación Navarra de Ergonomía (ANER), 2021) González Moreno, Miguel Ángel; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
Se realiza la identificación de los principales riesgos ergonómicos en las ITEAF, y en particular los asociados a los dos puestos de trabajo del “Inspector” y “Director técnico”, conforme se recoge en el Real Decreto 1702/2011, de 18 de noviembre, de inspecciones periódicas de los equipos de aplicación de productos fitosanitarios.
Open Access
On the lossy character of Y-branches and their analogy to Wilkinson power dividers
(Optica Publishing Group, 2024-11-04) Oña Valladares, Douglas; Hernández Martínez, Osmery; Ortega Gómez, Ángel; González-Andrade, David; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Y-branches are commonly used devices for power splitting and combining in various technological applications. Despite their widespread use, research on their design and analysis has been mostly focused on their characterization based on reflection and transmission when operating as power dividers, leaving aside an exhaustive consideration of all their possible modes of operation. Also, it has not been fully recognized that these devices have intrinsic losses. If these losses are not properly managed, they can negatively impact the network, but also open the door to new opportunities. In this context, this paper examines Y-bifurcation properties and their connection to Wilkinson's power dividers. Additionally, through numerical analysis, we demonstrate the possibility of integrating these devices into more complex optical networks. We use them as components in generalized power dividers and analog optical computational systems designed to filter out the maximum common phase component and avoid backward reflections for any input signal.
Open Access
A new methodology to easy integrate complementarity criteria in the resource assessment process for hybrid power plants: offshore wind and floating PV
(Elsevier, 2025-02-21) Frías Paredes, Laura; Gastón Romeo, Martín; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, OTRI project, reference number 2020 2143 0
The maturity of technologies of energy generation from renewable sources produces tense an increasing interest on hybrid power plant implementation. The combination of different resources, as wind and solar, introduces concepts as complementarity that must be taken into account when suitability of emplacements is made. This work presents a methodology to evaluate a geographic area under the perspective of installing hybrid wind and PV power plants. Therefore, it proposes a way to evaluate the complementarity among both resources that would avoid overestimation due to time delays and it also would offer a holistic procedure to identify the most suitable locations to host one of these hybrid power plants. The methodology is illustrated by evaluating the Off-shore Spanish area to install wind and floating PV plants and is flexible to adapt the evaluation according to dimension of each technology in the future plants. It is shown how the complementarity criteria as input in the site selection process improves the ordered of emplacements obtained when only resource amount is taken into account. The methodology can be used to identify more suitable areas in the initial stages of promoting hybrid power plants. Data from ERA5 and CAMS are used to analyze long term behavior of wind and solar resources.
Open Access
Quantum and thermal noise in coupled non-hermitian waveguide systems with different models of gain and loss
(De Gruyter, 2025-01-03) Hernández Martínez, Osmery; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Non-Hermitian (NH) photonic systems leverage gain and loss to open new directions for nanophotonic technologies. However, the quantum and thermal noise intrinsically associated with gain/loss affects the eigenvalue/eigenvector structure of NH systems, and thus the existence of exceptional points, as well as the practical noise performance of these systems. Here, we present a comparative analysis of the impact of different gain and loss mechanisms on the noise generated in gain-loss compensated NH waveguide systems. Our results highlight important differences in the eigenvalue/eigenvector structure, noise power, photon statistics and squeezing. At the same time, we identify some universal properties such as the occurrence of phase-transition points in parameter space and intriguing phenomena related to them, including coalescence of pairs of eigenvectors, gain-loss compensation, and linear scaling of the noise with the length of the waveguide. We believe that these results contribute to a better understanding of the impact of the gain/loss mechanism on the noise generated in NH systems.
Open Access
Spatiotemporal symmetries and energy-momentum conservation in uniform spacetime metamaterials
(American Chemical Society, 2024-11-13) Liberal Olleta, Íñigo; Ganfornina Andrades, Antonio; Vázquez Lozano, Juan Enrique; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Spacetime metamaterials are opening new regimes of light-matter interactions based on the breaking of temporal and spatial symmetries, as well as intriguing concepts associated with synthetic motion. In this work, we investigate the continuous spatiotemporal translation symmetry of spacetime metamaterials with uniform modulation velocity. Using Noether's theorem, we demonstrate that such symmetry entails the conservation of the energy momentum. We highlight how energy-momentum conservation imposes constraints on the range of allowed light-matter interactions within spacetime metamaterials, as illustrated with examples of the collision of electromagnetic and modulation pulses. Furthermore, we discuss the similarities and differences between the conservation of energy-momentum and relativistic effects. We believe that our work provides a step forward in clarifying the fundamental theory underlying spacetime metamaterials.
Open Access
Distributed vibration sensing based on optical vector network analysis
(IEEE, 2024-10-28) Loayssa Lara, Alayn; Vallifuoco, Raffaele; Zahoor, Rizwan; Zeni, Luigi; Sagüés García, Mikel; Minardo, Aldo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We introduce a novel method for distributed vibration sensing based on extracting the time-domain Rayleigh impulse response of an optical fiber from optical vector network analysis measurements. The optical-frequency-domain transfer function of the fiber is first measured, and then inverse Fourier transformed to provide the bandpass optical time-domain impulse response. Another relevant feature of the technique is that it enables excitation demodulation using the optical frequency dependence of the Rayleigh backscatter signal from the optical fiber, the so-called Rayleigh signature. This is the simplest method to obtain fully linear quantitative measurements of local changes in the strain or temperature experienced by the fiber and it is inherently free from signal fading impairments. Furthermore, the implementation of the technique uses a simple setup based on double-sideband modulation of a laser, self-homodyne detection with an optical hybrid, and narrow-bandwidth electrical signal acquisition and processing. We present proof-of-concept experiments to demonstrate the operation of the method with the measurement of dynamic strain and temperature perturbations in a 115-m optical sensing fiber with 16-cm spatial resolution and a sensitivity of 59 nHz. This sensing technique has the potential to provide high-sensitivity distributed measurements of tens-of-hertz excitations in hundreds-of-meters fibers, with centimeter spatial resolution. Therefore, it can become a valuable tool for structural health monitoring in application fields such as aerospace, marine, or civil engineering.
Open Access
Design and analysis of a two-stage cascade system for heating and hot water production in nearly zero-energy buildings using thermoelectric technology
(MDPI, 2024-12-16) Ordóñez, Javier ; Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Algarra Pérez, Fernando; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
This paper proposes an innovative system that integrates two thermoelectric heat pumps (one air–water and the other water–water) with two thermal storage tanks at different temperatures to provide heating and domestic hot water to a 73.3 m2 passive-house-certified dwelling in Pamplona (Spain). The air–water thermoelectric heat pump extracts heat from the ambient air and provides heat to a tank at intermediate temperature, which supplies water to a radiant floor. The water–water heat pump takes heat from this tank and provides heat to the other tank, at higher temperature, which supplies domestic hot water. The system performance and comfort conditions are computationally analyzed during the month of January under the climate of Pamplona and under different European climates. The COP of the system lays between 1.3 and 1.7, depending on the climate, because of the low COP of the air–water thermoelectric heat pump. However, it is able to provide water for the radiant floor and to maintain the temperature of the dwelling above 20 °C 99.8% of the time. Moreover, it provides domestic hot water at a temperature above 43 °C 99.9% of the time. Noteworthy is the fact that the water–water heat pump presents a COP close to 4, which opens up the possibilities of working in combination with more efficient heat pumps for the first stage.