Artículos (Física Aplicada I)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10849

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Photonic crystal beam splitter electrode in kesterite tandem solar cells: a numerical approach
(wiley, 2024-05) Barragán Sánchez-Lanuza, Miguel; Lillo Bravo, Isidoro; López Álvarez, José A.; Delgado Sánchez, José María; Universidad de Sevilla. Departamento de Física Aplicada I
The majority of numerical research on kesterite tandem solar cells has predominantly focused on a two-terminal (2T) configuration that utilizes an ideal tunnel junction. Herein, the performance of kesterite tandem solar cells by introducing a photonic crystal structure (1DPC) as intermediate layer in both three-terminal (3T) and four-terminal (4T) configurations is investigated. The photonic crystal (1DPC) is designed by stacking ITO and SiO2 layers with the terminal layer consisting of NiO. Optical properties of the 1DPC are modeled. This innovative approach offers several advantages. 1) The 1DPC selectively reflects lower wavelengths, effectively enhancing the short-circuit current density (Jsc) of the top subcell, while the solar irradiance spectrum at higher-wavelength optimum for the subcell is not affected. 2) The 1DPC serves as an intermediate electrode, needed for the 3T or 4T configuration. 3) Replacing the conventional Mo back contact with a NiO layer significantly boosts the open-circuit voltage (Voc) of the top subcell. The findings demonstrate that these configurations exhibit higher performance compared to previously reported results. Furthermore, the utilization of 3T and 4T configurations, incorporating the 1DPC as an electrical beam splitter, provides an effective and accurate design compared to the 2T configuration using ideal tunnel junctions.
Luminescent solar concentrators: Photo-stability analysis and long-term perspectives
(Elsevier, 2019-11) Delgado Sánchez, José María; Universidad de Sevilla. Departamento de Física Aplicada I
Luminescent Solar Concentrators (LSC) have been extensively analysed from the point of view of design to improve its performance, but there are still open questions about long-term stability at outdoor conditions, which reduce its commercial interest. A study of photo-stability of a LSC is presented in this work. The prototype consists in an organic dye, encapsulated at pilot scale (10 × 10 cm2) to reproduce real operating conditions. Outdoor monitoring and indoor aging tests are performed to evaluate what are the critical failures, their cause, and possible mitigation solutions to provide long-term stability to the LSC device. A correlation between encapsulating materials and dye photoluminescence properties is identified, which clarify the photo-degradation mechanism of the LSC. These results provide a better comprehension of the design strategies required to ensure the re
Zn(O,S) buffer layer deposited by High Vapor Transport Deposition (HVTD) for controlling band alignment of Cu2ZnSn(SxSe1-x)4 thin film solar cell heterojunction
(Wiley, 2022-10-26) Delgado Sánchez, José María; Universidad de Sevilla. Departamento de Física Aplicada I
The replacement of the CdS buffer layer is desirable for the development of non-toxic and environmentally friendly kesterite thin film solar cells. Band alignment is critical to the energy conversion of solar cells and achieving optimum design of the layers requires high control of the process. In this work, we report the band alignment dependence of the CZTSSe/Zn(O,S) interface using different oxygen concentrations, which results in a high controllability process for the energy levels of the buffer layers, which is desirable to achieve higher solar cell efficiencies. It is also demonstrated that a Zn(O,S) thin film layer can be deposited using a novel process: High Vapor Transport Deposition (HVTD). The main advantages observed are: 1) absorber and buffer layers can be deposited in the same vacuum reactor, thus avoiding atmospheric contamination; 2) no additional etching or annealing process is needed; and 3) the process conditions have accuracy control of the gas injection, which allows a precise tuning of the oxygen content in the film. Optimal oxygen concentration was determined to avoid spike-like CBO, achieving a conversion efficiency level of 6.87% for kesterite-based thin film solar cells with a Cd-free buffer layer.
Highly stable photoluminescence in vacuum-processed halide perovskite core-shell 1D nanostructures
(Wiley, 2024-10-01) Castillo Seoane, Javier; Contreras Bernal, Lidia; Rojas Ruiz, Teresa Cristina; Espinós Manzorro, Juan Pedro; Castro Méndez, Andrés Felipe; Correa Baena, Juan Pablo; Barranco Quero, Ángel; Sánchez Valencia, Juan Ramón; Borrás Martos, Ana Isabel; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Hybrid organometal halide perovskites (HP) present exceptional optoelectronic properties, but their poor long-term stability is a major bottleneck for their commercialization. Herein, a solvent-free approach to growing single-crystal organic nanowires (ONW) is presented, along with nanoporous metal oxide scaffolds and HP, to form a core@multishell architecture. The synthesis is carried out under mild vacuum conditions employing thermal evaporation for the metal-free phthalocyanine (H2Pc) nanowires, which are the core, plasma-enhanced chemical vapor deposition (PECVD) for the TiO2 shell, and co-evaporation of lead iodide (PbI2) and methylammonium iodide (CH3NH3I/MAI) for the CH3NH3PbI3 (MAPbI3/MAPI) perovskite shell. A detailed characterization of the nanostructures by electron microscopy, (S)-TEM, and X-ray diffraction, XRD, is presented, revealing a different crystallization of the HP depending on the template: while the growth on H2Pc nanowires induces the typical MAPI tetragonal structure, a low-dimensional phase (LDP) is observed on the 1D-TiO2 nanotubes. Such a combination yields an unprecedentedly stable photoluminescence emission over 20 h and over 300 h after encapsulation in polymethyl methacrylate (PMMA) under different atmospheres including N2, air, and high moisture levels. Moreover, the unique 1D morphology of the system, together with the high refractive index, allows for a strong waveguiding effect along the HP nanowire length.
Simulation conditions to compute the dispersion diagram of 3D periodic structures
(Institute of Electrical and Electronics Engineers, 2024-07) Wang, Hairu; Zetterstrom, Oskar; Castillo Tapia, Pilar; Mesa Ledesma, Francisco Luis; Quevedo Teruel, Óscar; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. TIC112: Microondas
In this work, we examine the methodology for numerically computing the dispersion diagram of three-dimensional periodic structures using commercial electromagnetic simulators. Examples of periodic structures based on body-centered cubic, face-centered cubic, and monoclinic lattices are used to illustrate this methodology. We first outline the characteristics of these structures in both physical and reciprocal spaces from a theoretical point of view. On this basis, we provide a comprehensive explanation of how to adjust the setting in simulation software commonly used in microwave engineering to generate the dispersion diagrams of these structures. The appropriate simulation conditions are tabulated to serve as a further guide for other researchers. This study also explores the influence of the elements of the unit cell on the dispersion characteristics. Additionally, we evaluate and contrast the dispersion properties of identical periodic elements when having simple cubic, body-centered cubic, and face-centered cubic arrangements. We found that symmetries, such as those seen in body-centered cubic and face-centered cubic arrangements, can improve the isotropy and maintain low-dispersion characteristics over a wider frequency range. The monoclinic structure is also taken as an example to demonstrate that the reported analysis method can be applied to the dispersion analysis of other more complex noncubic lattices. Our findings offer useful information for the examination and engineering of three-dimensional periodic structures, which can be used to design microwave and antenna devices.
On forward and backward modes in 1D periodic bounded structures
(Institute of Electrical and Electronics Engineers, 2024-10) Zetterstrom, Oskar; Rodríguez Berral, Raúl; Mesa Ledesma, Francisco Luis; Quevedo Teruel, Óscar; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. TIC112: Microondas
We discuss the issue of identifying the forward/backward nature of modes in bounded one-dimensional periodic structures. This identification is based on the possibility of adequately and uniquely defining the phase velocity in these types of structure. We propose a general definition of phase velocity for one-dimensional scalar waves and show that, according to that general definition, the voltage and current waves in nonhomogeneous lossless transmission lines with positive per-unit-length capacitance and inductance are necessarily forward waves. We analyze in detail the particular case of periodic transmission lines and question the conclusions about the forward/backward nature of their modal solutions that are traditionally drawn from the inspection of the Brillouin diagrams. Numerical results for the case of corrugated parallel-plate waveguides support the idea that all modes can be considered forward-like as long as a periodic transmission line model remains a sensible and reliable description of the problem. In more general scenarios, we show that an appropriate definition of the phase velocity can still be found for electromagnetic waves with at least one linearly polarized field and that they are also necessarily forward waves if they propagate through media with positive ε and μ parameters. Finally, we relate our discussion to the effective refractive index of periodic structures, highlighting that although its definition is not valid for a general periodic structure, it can be useful in many practical cases.
Electromagnetic bandgap based on a compact three-hole double-layer periodic structure
(Institute of Electrical and Electronics Engineers, 2024-01) Herrán Ontañón, Luis Fernando; Chen, Qiao; Mesa Ledesma, Francisco Luis; Quevedo Teruel, Óscar; Universidad de Sevilla. Departamento de Física Aplicada I; European Cooperation in Science and Technology (COST); Principado de Asturias; Universidad de Sevilla. TIC112: Microondas
We propose and study a new type of double-layer holey structure with a wide bandgap. The structure can have glide symmetry in two orthogonal directions but not 2-D glide symmetry. We report results in terms of dispersion diagrams calculated with the eigensolver of a commercial solver, as well as with a multimode transfer matrix approach that permits an accurate calculation of the attenuation constant. The results demonstrate that the bandgap of the proposed structure can provide a wider fractional bandwidth and a larger attenuation constant than those of a 2-D glide-symmetric holey configuration. Therefore, this new type of periodic structure can be advantageous in preventing leakage in gap waveguide technology or, in general, parallel plate configurations and filters. The operation of this new unit cell is experimentally demonstrated with a double-flange configuration between 40–60 GHz.
Development of a hyperspectral imaging protocol for painting applications at the University of Seville
(MDPI, 2024-10-23) Vasco, Giovanna; Aureli, Hélène; Fernández Lizaranzu, Isabel; Moreno Soto, Javier; Kriznar, Anabelle; Parrilla Giráldez, Rubén; Gómez González, Emilio; Respaldiza Galisteo, Miguel Ángel; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Escultura e Historia de las Artes Plásticas; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia Estatal de Investigación. España
In the last decade, the hyperspectral imaging (HSI) method allowed performing non-invasive analysis in the field of cultural heritage. However, a considerable limitation was given by redundant and time-consuming features, with the necessary application of statistical algorithms and image-processing tools to extract relevant information. In this study, the Centro Nacional de Aceleradores (CNA) and the Group of Interdisciplinary Physics (GFI) of the School of Engineering (ETSI) of the University of Seville tested the application of three different hyperspectral cameras in the visible and near-infrared (VNIR) and short-wave infrared (SWIR) range for the investigation of an ancient painting. A reference-based procedure was realised to build a starting personal library and to evaluate the best working conditions for non-invasive and non-destructive characterisation with data treatment using the commercially available software Evince® and Specim IQ® to apply, respectively, the Principal Component Analysis (PCA) model functions and the classification method. The evaluation of the protocol was tested by acquiring complementary information by X-ray fluorescence (XRF), Ultraviolet Luminescence (UVL) imaging, and Infrared Reflectography (IRR). This exploration established a simplified protocol to analyse the large collection of paintings of the Archbishop’s Palace and the Cathedral of Seville.
Oscillatory instability and stability of stationary solutions in the parametrically driven, damped nonlinear Schrödinger equation
(ArXiv, 2024-11-15) Carreño Navas, Fernando; Álvarez Nodarse, Renato; Quintero, Niurka R.; Universidad de Sevilla. Departamento de Análisis Matemático; Universidad de Sevilla. FQM415: Modelado Físico-Matemático de Sistemas no Lineales
We found two stationary solutions of the parametrically driven, damped nonlinear Schrö\-dinger equation with nonlinear term proportional to $|\psi(x,t)|^{2 \kappa} \psi(x,t)$ for positive values of $\kappa$. By linearizing the equation around these exact solutions, we derive the corresponding Sturm-Liouville problem. Our analysis reveals that one of the stationary solutions is unstable, while the stability of the other solution depends on the amplitude of the parametric force, damping coefficient, and nonlinearity parameter $\kappa$. An exceptional change of variables facilitates the computation of the stability diagram through numerical solutions of the eigenvalue problem as a specific parameter $\varepsilon$ varies within a bounded interval. For $\kappa <2$ , an oscillatory instability is predicted analytically and confirmed numerically. Our principal result establishes that for $\kappa \ge 2$, there exists a critical value of $\varepsilon$ beyond which the unstable soliton becomes stable, exhibiting oscillatory stability.
129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process
(Elsevier, 2022) Lérida Toro, Victoria; Abascal Ruíz, Unai; Villa Alfageme, María; Klar, Jessica K.; Hicks, Natalie; López Gutiérrez, José María; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH⋅HCl) and so dium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in so lution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.
Distribution of 1 236U in the U.S. GEOTRACES Eastern Pacific Zonal Transect and its use as a 2 water mass tracer
(Elsevier, 2019) Villa Alfageme, María; Chamizo Calvo, Elena; Kenna, Timothy C.; López Lora, Mercedes; Casacuberta, Nuria; Chang, Clara H.; Masqué, Pere; Christi, Marcus; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
We report dissolved concentrations of the long-lived radioisotope 236U measured in the water column along the 2013 US GEOTRACES Eastern Pacific Zonal Transect (GP16). This transect followed a 10–15°S line from Manta, Ecuador, to Papeete, Haiti, French Polynesia, crossing the southern East Pacific Rise, intercepting one of the largest hydrothermal plumes as well as a productivity gradient, which includes the upwelling zone and associated low oxygen waters offshore from Peru and the oligotrophic sub-tropical gyre. Accelerator Mass Spectrometry was used to measure dissolved seawater 236U concentrations as low as 1 × 103 atom kg−1, which are among the lowest levels reported to date. Differences in upper water column 236U distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect. The distribution of 236U, both in depth and geographically, provides complementary information to that obtained from Δ14C and helium isotopes, demonstrating that 236U concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the EPZT (Jenkins et al., 2017). For example, we observe minimum 236U concentrations along the EPZT between 2000 and 3000 m that are consistent with contributions attributed to Pacific Deep Water. We also observe increases in 236U below 3000 m at the eastern and western termini of the EPZT. This is consistent with contributions associated with Antarctic Bottom Water and Lower Circumpolar Deep Water. Our results indicate that 236U may be used in conjunction with Δ14C and 3He isotopes as an additional tool with which to identify and resolve contributions from different water masses in the Pacific Ocean.
Magnetron sputtered ß-Ti coatings for biomedical application: A HiPIMS approach to improve corrosion resistance and mechanical behavior
(Elsevier, 2025-01-30) Sánchez López, Juan Carlos; Fortio Godinho, Vanda Cristina; López Santos, Carmen; Navarro González, Paula; Rodríguez-Albelo, Luisa Marleny; Sánchez Pérez, Miriam; Jiménez Piqué, Emilio; Torres Hernández, Yadir; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
This work presents the surface modification of commercially pure Ti specimens (c.p.-Ti) prepared by conventional powder metallurgy by depositing a thin film of a ß-Ti alloy (Ti-35Nb-7Zr-5Ta, wt. %, TNZT). Two types of pulsed technologies: conventional (p-DC) and high-power impulse magnetron sputtering (HiPIMS), with and without bias assistance (−60 V) under similar power conditions (250 W) were applied on titanium specimens and silicon substrates leading to different film morphologies and functional properties. Microstructural, X-ray diffraction, nanoindentation, surface wetting, XPS and electrochemical impedance measurements were done to characterize their functionality. All the coatings presented a reduced Young’s Modulus (E ≤ 80GPa) compared to the bulk Ti, representing a reduction of more than 30 %. This decrease can significantly contribute to the reduction of the stress-shielding effect, mitigating the risk of implant loosening and failure. The hardness values of TNZT coatings, slightly lower than c.p.-Ti substrate, range from 4.1 to 4.7 GPa. XPS analysis shows a passivation layer of TiO2, Nb2O5, and ZrO2, which offers high impedance and excellent corrosion resistance. The best compromise between mechanical and corrosion properties is achieved with the HiPIMS technology, thanks to its compact film microstructure with high electrical resistance, despite its limited thickness of about 1 μm.
Stability of Breathers for a Periodic Klein–Gordon Equation
(MDPI, 2024-09-04) Chirilus-Bruckner, Martina; Cuevas-Maraver, Jesús; Kevrekidis, Panayotis G.; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. FQM280: Física no Lineal
The existence of breather-type solutions, i.e., solutions that are periodic in time and exponentially localized in space, is a very unusual feature for continuum, nonlinear wave-type equations. Following an earlier work establishing a theorem for the existence of such structures, we bring to bear a combination of analysis-inspired numerical tools that permit the construction of such waveforms to a desired numerical accuracy. In addition, this enables us to explore their numerical stability. Our computations show that for the spatially heterogeneous form of the ϕ4 model considered herein, the breather solutions are generically unstable. Their instability seems to generically favor the motion of the relevant structures. We expect that these results may inspire further studies towards the identification of stable continuous breathers in spatially heterogeneous, continuum nonlinear wave equation models.
Numerical modelling of radionuclide uptake by bluefin tuna along its migration routes in the Mediterranean Sea after a nuclear accident
(Elsevier, 2024-09-20) Cortés Parejo, María del Carmen; Periáñez Rodríguez, Raúl; Block, Bárbara A.; Castleton, Michael R.; Cermeño, Pablo; Dedman, Simon; Universidad de Sevilla. Departamento de; Universidad de Sevilla. Departamento de Física Aplicada I
A numerical model which simulates the adsorption of radionuclides by migrating bluefin tuna in the Mediterranean Sea is described, in order to determine the level of contamination of these fish after a hypothetical nuclear accident and thus be able to assess the possible impact on human consumption. A 4–species foodweb model is incorporated into a Lagrangian model describing physical transport (advection, mixing, radioactive decay and interactions of radionuclides with sediments). Tuna is the last trophic level in the foodweb model and the equation providing the temporal evolution of radionuclide concentration in its flesh is solved along the fish trajectories, which were obtained through electronic tagging of fishes. The model was applied to the western Mediterranean, where several worst–case hypothetical accidents were simulated, both from a coastal nuclear power plant and from a vessel. Resulting 137Cs concentrations in migrating tuna were similar, or slightly higher, than reported background concentrations in these fishes and well below established safety levels. Maximum calculated concentrations in tuna flesh is in the order of 1 Bq/kg (wet weight). This is due to the rapid movement of the fishes, which spend only limited time over the most contaminated spots.
Ceramic barrier layers for flexible thin film solar cells on metallic substrates: A laboratory scale study for process optimization and barrier layer properties
(American Chemical Society, 2014) Delgado Sánchez, José María; Guilera, Nuria; Francesch, Laia; Alba, María D.; López, Laura; Sánchez, Emilio; Universidad de Sevilla. Departamento de Física Aplicada I
Flexible thin film solar cells are an alternative to both utility-scale and building integrated photovoltaic installations. The fabrication of these devices over electrically conducting low-cost foils requires the deposition of dielectric barrier layers to flatten the substrate surface, provide electrical isolation between the substrate and the device, and avoid the diffusion of metal impurities during the relatively high temperatures required to deposit the rest of the solar cell device layers. The typical roughness of low-cost stainless-steel foils is in the hundred-nanometer range, which is comparable or larger than the thin film layers comprising the device and this may result in electrical shunts that decrease solar cell performance. This manuscript assesses the properties of different single-layer and bilayer structures containing ceramics inks formulations based on Al2O3, AlN, or Si3N4 nanoparticles and deposited over stainless-steel foils using a rotogravure printing process. The best control of the substrate roughness was achieved for bilayers of Al2O3 or AlN with mixed particle size, which reduced the roughness and prevented the diffusion of metals impurities but AlN bilayers exhibited as well the best electrical insulation properties.
Observation of stochastic resonance in directed propagation of cold atoms
(American Physical Society, 2022-12) Staron, Alexander; Jiang, Kefeng; Scoggins, Casey; Wingert, Daniel; Cubero Gómez, David; Bali, Samir; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Ciencia e Innovación (MICIN). España
Randomly diffusing atoms confined in a dissipative optical lattice are illuminated by a weak probe of light. The probe transmission spectrum reveals directed atomic propagation that occurs perpendicular to the direction of probe beam propagation. Resonant enhancement of this directed propagation is observed as we vary the random photon scattering rate. We experimentally characterize this stochastic resonance as a function of probe intensity and lattice well depth. A simple model reveals how the probe-excited atomic density waves and optical pumping rates conspire to create directed atomic propagation within a randomly diffusing sample.
Some considerations on the dependence to numerical schemes of Lagrangian radionuclide transport models for the aquatic environment
(Elsevier, 2023-05) Periáñez Rodríguez, Raúl; Brovchenko, I.; Jung, K. T.; Kim, K. O.; Liptak, L.; Little, A.; Kobayashi, T.; Maderich, V.; Min, B. I.; Suh, K. S.; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Lagrangian models present several advantages over Eulerian models to simulate the transport of radionuclides in the aquatic environment in emergency situations. A radionuclide release is simulated as a number of particles whose trajectories are calculated along time and thus these models do not require a spatial discretization (although it is always required in time). In this paper we investigate the dependence of a Lagrangian model output with the grid spacing which is used to calculate concentrations from the final distribution of particles, with the number of particles in the simulation and with the interpolation schemes which are required because of the discrete nature of the water circulation data used to feed the model. Also, a Lagrangian model may describe the exchanges of radionuclides between phases (liquid and solid), which is done in terms of transition probabilities. The dependence of these probabilities with time step is analyzed as well. It was found that the optimum grid size used to calculate concentrations should be carefully checked, and that temporal interpolation is more significant than spatial interpolation to obtain a more accurate solution. A method to estimate the number of particles required to have a certain accuracy level is proposed. Finally, it was found that for low sediment concentrations and small radionuclide , exact equations for the transition probabilities should be used; and that phase transitions introduce a stability condition as in Eulerian models.
The Transport of Radionuclides Released From Nuclear Facilities and Nuclear Wastes in the Marine Environment at Oceanic Scales
(The Korean Radioactive Waste Society, 2022-09) Periáñez Rodríguez, Raúl; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
The transport of radionuclides at oceanic scales can be assessed using a Lagrangian model. In this review an application of such a model to the Atlantic, Indian and Pacific oceans is described. The transport model, which is fed with water currents provided by global ocean circulation models, includes advection by three–dimensional currents, turbulent mixing, radioactive decay and adsorption/release of radionuclides between water and bed sediments. Adsorption/release processes are described by means of a dynamic model based upon kinetic transfer coefficients. A stochastic method is used to solve turbulent mixing, decay and water/sediment interactions. The main results of these oceanic radionuclide transport studies are summarized in this paper. Particularly, the potential leakage of 137Cs from dumped nuclear wastes in the north Atlantic region was studied. Furthermore, hypothetical accidents, similar in magnitude to the Fukushima accident, were simulated for nuclear power plants located around the Indian Ocean coastlines. Finally, the transport of radionuclides resulting from the release of stored water, which was used to cool reactors after the Fukushima accident, was analyzed in the Pacific Ocean.
Setting a comprehensive strategy to face the runback icing phenomena
(Elsevier, 2023-07) Mora, Julio; García, Paloma; Carreño, Francisco; González, Miguel; Gutiérrez, Marcos; Montes, Laura; Rico-Gavira, Víctor Joaquín; López Santos, Carmen; Vicente, Adrián; Rivero, Pedro; Rodríguez, Rafael; Larumbe, Silvia; Acosta, Carolina; Ibáñez-Ibáñez, Pablo; Corozzi, Alessandro; Raimondo, Mariarosa; Kozera, Rafal; Przybyszewski, Bartlomiej; González-Elipe, Agustín R.; Borrás, Ana; Redondo, Francisco; Agüero, Alina; Universidad de Sevilla. Departamento de Física Aplicada I; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Consejo Superior de Investigaciones Científicas (CSIC)
The development of anti-icing robust surfaces is a hot topic nowadays and particularly crucial in the aeronautics or wind energy sectors as ice accretion can compromise safety and power generation efficiency. However, the current performance of most anti-icing strategies has been proven insufficient for such demanding applications, particularly in large unprotected zones, which located downstream from thermally protected areas, may undergo secondary icing. Herein, a new testing methodology is proposed to evaluate accretion mechanisms and secondary icing phenomena through, respectively, direct impact and running-wet processes and systematically applied to anti-icing materials including commercial solutions and the latest trends in the state-of-the-art. Five categories of materials (hard, elastomeric, polymeric matrix, SLIPS and superhydrophobic) with up to fifteen formulations have been tested. This Round-Robin approach provides a deeper understanding of anti-icing mechanisms revealing the strengths and weaknesses of each material. The conclusion is that there is no single passive solution for anti-ice protection. Thus, to effectively protect a given real component, different tailored materials fitted for each particular zone of the system are required. For this selection, shape analysis of such a component and the impact characteristics of water droplets under real conditions are needed as schematically illustrated for aeronautic turbines.
Geodesic Half-Maxwell Fish-Eye-Lens Antenna
(Institute of Electrical and Electronics Engineers, 2023-03) Yang, Shiyi; Chen, Qiao; Mesa Ledesma, Francisco Luis; Fonseca, Nelson J. G.; Quevedo Teruel, Óscar; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. TIC112: Microondas
We propose and implement a geodesic half-Maxwell fish-eye (MFE)-lens antenna. The lens was optimized using an in-house physical optics (PO) code adapted for generalized geodesic lenses. The final antenna design was validated with commercial electromagnetic simulation software. The antenna combines a modulated geodesic half-MFE lens and a transition to a linear flare, which is needed to preserve the linear polarization in the aperture. The antenna prototype, designed to operate in the Ka -band, was manufactured with computer numerical control (CNC) milling and measured in an anechoic chamber. The design provides continuous beam scanning because of a mechanically actuated feed. Promising beam scanning properties are demonstrated in an angular range of ±45° with a scan loss below 3 dB, as well as good frequency stability from 26 to 32 GHz. Since the antenna is fully metallic, its radiation efficiency is high (approximately 90%).

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