Artículos (Ingeniería y Ciencia de los Materiales y del Transporte)
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Artículo Magnetron sputtered ß-Ti coatings for biomedical application: A HiPIMS approach to improve corrosion resistance and mechanical behavior(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 Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Tecnología Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesThis 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 , Nb₂ O₅, 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.Artículo Chitosan–Type-A-Gelatin Hydrogels Used as Potential Platforms in Tissue Engineering for Drug Delivery(Multidisciplinary Digital Publishing Institute (MDPI), 2024-07) Mehdi-Sefiani, Hanaa; Granados-Carrera, Carmen María; Romero García, Alberto; Chicardi Augusto, Ernesto; Domínguez Robles, Juan; Pérez-Puyana, Víctor Manuel; Universidad de Sevilla. Departamento de Ingeniería Química; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica; Universidad de Sevilla; European Union (UE); Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Universidad de Sevilla. TEP229: Tecnología y Diseño de Productos Multicomponentes; Universidad de Sevilla. TEP973: Tecnología de Polvos y Corrosión; Universidad de Sevilla. CTS547: Caracterización y Optimización Estadística de MedicamentosHydrogels are materials made of crosslinked 3D networks of hydrophilic polymer chains that can absorb and retain significant amounts of water due to their hydrophilic structure without being dissolved. In relation to alternative biomaterials, hydrogels offer increased biocompatibility and biodegradability, giving them distinct advantages. Thus, hydrogel platforms are considered to have the potential for the development of biomedical applications. In this study, the main objective was the development of hybrid hydrogels to act as a drug delivery platform. These hydrogels were made from chitosan (CH) and type A gelatin (G), two natural polymers that provide a supportive environment for cellular attachment, viability, and growth, thanks to their unique properties. Particularly, the use of gelatins for drug delivery systems provides biodegradability, biocompatibility, and non-toxicity, which are excellent properties to be used in the human body. However, gelatins have some limitations, such as thermal instability and poor mechanical properties. In order to improve those properties, the aim of this work was the development and characterization of hybrid hydrogels with different ratios of CH–G (100–0, 75–25, 50–50, 25–75, 0–100). Hydrogels were characterized through multiple techniques, including Fourier transform infrared (FTIR) spectroscopy, rheological and microstructural studies, among others. Moreover, a model hydrophilic drug molecule (tetracycline) was incorporated to evaluate the feasibility of this platform to sustain the release of hydrophilic drugs, by being tested in a solution of Phosphate Buffer Solution at a pH of 7.2 and at 37 °C. The results revealed that the synergy between chitosan and type A gelatin improved the mechanical properties as well as the thermal stability of it, revealing that the best ratios of the biopolymers are 50–50 CH–G and 75–25 CH–G. Thereby, these systems were evaluated in a controlled release of tetracycline, showing a controlled drug delivery of 6 h and highlighting their promising application as a platform for controlled drug release.Artículo Sol-gel-derived calcium silicate cement incorporating collagen and mesoporous bioglass nanoparticles for dental pulp therapy(Elsevier, 2024-11) Simila, Hazel O.; Anselmi, Caroline; Cardoso, Lais M.; Dal-Fabbro, Renan; Beltrán, Ana M.; Bottino, Marco C.; Boccaccini, Aldo R.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Deutscher Akademischer Austauschtdienst (DAAD); Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesObjective Calcium silicate cements (CSCs) are often used in endodontics despite some limitations related to their physical properties and antibacterial efficacy. This study aimed to develop and demonstrate the viability of a series of CSCs that were produced by sol-gel method and further modified with mesoporous bioactive glass nanoparticles (MBGNs) and collagen, for endodontic therapy. Methods Calcium silicate (CS) particles and MBGNs were synthesized by the sol-gel method, and their elemental, molecular, and physical microstructure was characterized. Three CSCs were developed by mixing the CS with distilled water (CS+H2O), 10 mg/mL collagen solution (CS+colH2O), and MBGNs (10 %) (CSmbgn+colH2O). The mixing (MT) and setting (ST) times of the CSCs were determined, while the setting reaction was monitored in real-time. Antibacterial efficacy against Enterococcus faecalis (E. faecalis) and regenerative potential on dental pulp stem cells (DPSCs) were also analyzed. Results The CS+H2O displayed a ST comparable to commercial products, while CSmbgn+colH2O achieved the longest MT of 68 s and the shortest ST of 8 min. All the experimental CSCs inhibited the growth of E. faecalis. Additionally, compared to the control group, CSCs supported cell proliferation and spreading and mineralized matrix production, regardless of their composition. Significance Tested CSCs presented potential as candidates for pulp therapy procedures. Future research should investigate the pulp regeneration mechanisms alongside rigorous antibacterial evaluations, preferably with multi-organism biofilms, executed over extended periodsArtículo Predicting Rail Corrugation Based on Convolutional Neural Networks Using Vehicle’s Acceleration Measurements(2024-07) Haghbin, Masoud; Chiachío Ruano, Juan; Muñoz Moreno, Sergio; Escalona Franco, José Luis; Guillén López, Antonio Jesús; Crespo Márquez, Adolfo; Cantero-Chinchilla, Sergio; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. Departamento de Organización Industrial y Gestión de Empresas I; Junta de Andalucía; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP134: Organización Industrial; Universidad de Sevilla. TEP111: Ingeniería MecánicaThis paper presents a deep learning approach for predicting rail corrugation based on on-board rolling-stock vertical acceleration and forward velocity measurements using One-Dimensional Convolutional Neural Networks (CNN-1D). The model’s performance is examined in a 1:10 scale railway system at two different forward velocities. During both the training and test stages, the CNN-1D produced results with mean absolute percentage errors of less than 5% for both forward velocities, confirming its ability to reproduce the corrugation profile based on real-time acceleration and forward velocity measurements. Moreover, by using a Gradient-weighted Class Activation Mapping (Grad-CAM) technique, it is shown that the CNN-1D can distinguish various regions, including the transition from damaged to undamaged regions and one-sided or two-sided corrugated regions, while predicting corrugation. In summary, the results of this study reveal the potential of data-driven techniques such as CNN-1D in predicting rails’ corrugation using online data from the dynamics of the rolling-stock, which can lead to more reliable and efficient maintenance and repair of railways.Artículo Enhancing alginate dialdehyde-gelatin (ADA-GEL) based hydrogels for biofabrication by addition of phytotherapeutics and mesoporous bioactive glass nanoparticles (MBGNs)(SAGE Publications, 2024-09) Bider, Faina; Gunnella, Chiara; Reh, Jana T.; Clejanu, Corina-Elena; Kuth, Sonja; Beltrán, Ana M.; Boccaccini, Aldo R.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesThis study explores the 3D printing of alginate dialdehyde-gelatin (ADA-GEL) inks incorporating phytotherapeutic agents, such as ferulic acid (FA), and silicate mesoporous bioactive glass nanoparticles (MBGNs) at two different concentrations. 3D scaffolds with bioactive properties suitable for bone tissue engineering (TE) were obtained. The degradation and swelling behaviour of films and 3D printed scaffolds indicated an accelerated trend with increasing MBGN content, while FA appeared to stabilize the samples. Determination of the degree of crosslinking validated the increased stability of hydrogels due to the addition of FA and 0.1% (w/v) MBGNs. The incorporation of MBGNs not only improved the effective moduli and conferred bioactive properties through the formation of hydroxyapatite (HAp) on the surface of ADA-GEL-based samples but also enhanced VEGF-A expression of MC3T3-E1 cells. The beneficial impact of FA and low concentrations of MBGNs in ADA-GEL-based inks for 3D (bio)printing applications was corroborated through various printing experiments, resulting in higher printing resolution, as also confirmed by rheological measurements. Cytocompatibility investigations revealed enhanced MC3T3-E1 cell activity and viability. Furthermore, the presence of mineral phases, as confirmed by an in vitro biomineralization assay, and increased ALP activity after 21 days, attributed to the addition of FA and MBGNs, were demonstrated. Considering the acquired structural and biological properties, along with efficient drug delivery capability, enhanced biological activity, and improved 3D printability, the newly developed inks exhibit promising potential for biofabrication and bone TE.Artículo Unveiling the Impact of Gelation Temperature on the Rheological and Microstructural Properties of Type A Gelatin Hydrogels(MDPI, 2024) Mehdi-Sefiani, Hanaa; Chicardi Augusto, Ernesto; Romero García, Alberto; Pérez-Puyana, Víctor Manuel; Universidad de Sevilla. Departamento de Ingeniería Química; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de SevillaGelatin-based hydrogels have garnered significant attention in the fields of drug delivery systems and tissue engineering owing to their biodegradability, biocompatibility, elasticity, flexibility and nontoxic nature. However, there is a lack of information regarding type-A-gelatin-based hydrogels. In this sense, the main aim of this work was the evaluation of the properties of type-A-gelatin-based hydrogel achieved using two different gelation temperatures (4 °C and 20 °C). Thus, the main novelty of this study lies in the analysis of the impact of gelation time on the rheological and microstructural properties of type-A-gelatin-based hydrogels. Moreover, the addition of a drug was also analyzed in order to evaluate the hydrogels’ behavior as a drug delivery system. For this purpose, rheological (strain, frequency sweep tests and flow curves) and microstructural (SEM) characterizations were carried out. The results demonstrated that lowering the gelation temperature improved the rheological properties of the systems, obtaining hydrogels with an elastic modulus of 20 kPa when processing at 4 °C. On the other hand, the increase in the gelation temperature improved the critical strain of the systems at low temperatures. In conclusion, this work showed the feasibility of producing hydrogels with potential application in drug delivery with different properties, varying the testing temperature and incorporating tetracycline into their formulation.Artículo PVA-gelatine based hydrogel loaded with astaxanthin and mesoporous bioactive glass nanoparticles for wound healing(Elsevier, 2024-11) Hernández Rivera, Gabriela; Váldez, Hugo A.; Arango-Ospina, Marcela; Delgado, Juan Francisco; Aguilar-Rabiela, Arturo E.; Gorgojo, Juan Pablo; Zhang, Huijun; Beltrán, Ana M.; Boccaccini, Aldo R.; Sánchez, Mirna Lorena; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesAstaxanthin (AST) is a potent antioxidant phytochemical used in wound healing with promising results in-vitro. However, AST incorporation into clinical practice still faces challenges related to the susceptibility of AST to instability. One of the most innovative solutions proposed is the encapsulation of AST into hydrogels. This study focuses on innovating the wound healing potential of AST-containing hydrogels by introducing silicate mesoporous bioactive glass nanoparticles (MBGNs). These nanoparticles release biologically active ions that accelerate cell proliferation and migration. The results showcase an innovative synergistic effect between 1 μg/mL of AST with 100 μg/mL of MBGNs, outperforming the individual proliferation effect of AST or MBGNs alone. Separately, these compounds were encapsulated in physical and chemical cross-linked hydrogel for the compound protection and delivery, finding that PVA-gelatine hydrogels are a suitable matrix for the delivery of AST and MBGNs. Physically crosslinked hydrogels showed particularly convenient characteristics for potential clinical implementation while maintaining the synergetic effect of AST and MBGNs. Although chemically crosslinked hydrogels exhibited suitable characteristics as a vehicle for AST in biological assays, cell proliferation was reduced by 57 %. The results of this research open avenues for exploring the development of new composite matrices for the co-delivery of phytochemicals and MBGNs for cutting-edge biomedical applications.Artículo Enhancing alginate dialdehyde-gelatin (ADA-GEL) based hydrogels for biofabrication by addition of phytotherapeutics and mesoporous bioactive glass nanoparticles (MBGNs)(SAGE Publications, 2024-09) Bider, Faina; Gunnella, Chiara; Reh, Jana T.; Clejanu, Corina-Elena; Kuth, Sonja; Beltrán, Ana M.; Boccaccini, Aldo R.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesThis study explores the 3D printing of alginate dialdehyde-gelatin (ADA-GEL) inks incorporating phytotherapeutic agents, such as ferulic acid (FA), and silicate mesoporous bioactive glass nanoparticles (MBGNs) at two different concentrations. 3D scaffolds with bioactive properties suitable for bone tissue engineering (TE) were obtained. The degradation and swelling behaviour of films and 3D printed scaffolds indicated an accelerated trend with increasing MBGN content, while FA appeared to stabilize the samples. Determination of the degree of crosslinking validated the increased stability of hydrogels due to the addition of FA and 0.1% (w/v) MBGNs. The incorporation of MBGNs not only improved the effective moduli and conferred bioactive properties through the formation of hydroxyapatite (HAp) on the surface of ADA-GEL-based samples but also enhanced VEGF-A expression of MC3T3-E1 cells. The beneficial impact of FA and low concentrations of MBGNs in ADA-GEL-based inks for 3D (bio)printing applications was corroborated through various printing experiments, resulting in higher printing resolution, as also confirmed by rheological measurements. Cytocompatibility investigations revealed enhanced MC3T3-E1 cell activity and viability. Furthermore, the presence of mineral phases, as confirmed by an in vitro biomineralization assay, and increased ALP activity after 21 days, attributed to the addition of FA and MBGNs, were demonstrated. Considering the acquired structural and biological properties, along with efficient drug delivery capability, enhanced biological activity, and improved 3D printability, the newly developed inks exhibit promising potential for biofabrication and bone TE.Artículo Modifying the size of Nickel metallic particles by H2/CO treatment in Ni/ZrO2 methane dry reforming catalysts(American Chemical Society, 2011-01) González de la Cruz, Víctor Manuel; Pereñíguez Rodríguez, Rosa María; Ternero Fernández, Fátima; Holgado, Juan Pedro; Caballero Martínez, Alfonso; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Educación y Ciencia (MEC). España; Junta de Andalucía; Universidad de Sevilla. TEP971: Ingeniería de Materiales AvanzadosThe effect of a reduction process with CO or H2 on the size of nickel particles in Ni/ZrO2 dry methane reforming catalysts have been studied by means of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance FTIR Spectroscopy (DRIFTS). Our results clearly indicate that a high temperature treatment with CO increases the dispersion of the nickel metallic phase. XAS results have shown a lower coordination number of Ni in the sample treated with CO than that reduced with H2. From the DRIFTS results, it can be established that, under the CO treatment, the formation of Ni(CO)4 complexes corrodes the nickel particles, decreasing their size. The formation of these gas molecules occurs without measurable losses of nickel from the catalyst which maintains the same nickel content after the hydrogen or the CO treatment at high temperature. Therefore, this airborne nickel compound, by colliding with the zirconia surface, must deposit the nickel metal atoms around onto the support. This behavior is evidence of an important interaction between nickel and zirconia surface as unlike other supports there is no losses of nickel during the dispersion process on zirconia. Although different effects of CO on nickel catalysts have been previously described, we have found for the first time several experimental evidences demonstrating the whole redispersion phenomenon.Artículo Study of nanostructured Ni/CeO2 catalysts prepared by combustion synthesis in dry reforming of methane(Elsevier, 2010-08) González de la Cruz, Víctor M.; Ternero Fernández, Fátima; Pereñíguez Rodríguez, Rosa María; Caballero Martínez, Alfonso; Holgado, Juan Pedro; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TEP971: Ingeniería de Materiales AvanzadosThis work reports the study of several catalysts of Ni–CeO2 active for dry methane reforming process (CH4 + CO2 → 2CO + 2H2). The use of Ni as active phase is highly preferred, due to its availability, high activity and low cost, although its main lack is the coke formation on the surface of Ni metal particles, resulting in a severe deactivation. Here we report a new synthesis method that allows a simple, effective and fast way to prepare Ni–CeO2 catalysts, in a wide range of metallic loadings, resulting in all the cases in well-formed NiO crystallites with sizes in the range of 12–18 nm. The use of CeO2 as a support has been based on its massive use in TWC catalysts formulations, where it is recognized to activate CH4 and lower hydrocarbon dissociation. Moreover, CeO2 has been reported to have an intrinsic activity in the CH4 reforming reaction. Besides the metallic loading, several factors that control the preparation method of the catalyst have been varied, in order to optimize their performance. Most of the catalysts prepared show activity and selectivity values close to thermodynamic ones, maintaining a good stability on long periods of time and severe conditions. Nevertheless, formation of some carbon nano-fibers has been observed, which could result in a drawback for their application at large scale.Artículo In Situ XAS Study of Synergic Effects on Ni–Co/ZrO2 Methane Reforming Catalysts(American Chemical Society, 2011-12) González de la Cruz, Víctor Manuel; Ternero Fernández, Fátima; Holgado, Juan Pedro; Pereñíguez Rodríguez, Rosa María; Caballero Martínez, Alfonso; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Educación y Ciencia (MEC). España; Junta de Andalucía; Universidad de Sevilla. TEP971: Ingeniería de Materiales AvanzadosFour different mono and bimetallic Ni–Co/ZrO2 catalysts have been studied by means of in situ XAS, X-ray diffraction, TPR, and measurements of the catalytic activity in the dry reforming reaction of methane (DRM). Even though the cobalt monometallic system has no activity for the methane reforming reaction, both bimetallic catalysts (with 1:1 and 1:2 Ni/Co ratio, respectively), showed a better activity and stability than the nickel monometallic system. The XRD data indicate that a mixed cobalt–nickel spinel is formed by calcination of the precursor solids, leading to the formation of an alloy of both metals after reduction in hydrogen. In situ XAS experiments showed a much better resistance of metals in the bimetallic systems to be oxidized under reaction conditions at temperatures until 750 °C. After these results, we proposed the formation in the bimetallic systems of a more reducible nickel–cobalt alloy phase, which remains completely metallic in contact with the CO2/CH4 reaction mixture at any temperature. The presence of adjacent nickel and cobalt sites seems to avoid the deactivation of cobalt in the DRM reaction. In the case of cobalt sites, the presence of adjacent nickel atoms seems to prevent the deposition of carbon over the cobalt sites, now showing its higher activity in the dry reforming reaction. Simultaneously, this higher activity of the cobalt sites in the bimetallic system produces more hydrogen as a product, maintaining the nickel atoms completely reduced under reaction conditions. This synergic effect accounts for the better performance of the bimetallic systems and points at both, the oxidation state of nickel particles under reaction conditions and the carbon deposition processes, as important factors responsible for differences in catalytic activities and stabilities in this hydrocarbon reaction.Artículo Problems in using individual x-by-wire cornering modules(Inderscience Enterprises Ltd., 2014) Morales Sánchez, Francisco José; Wideberg, Johan; Trigell, Annika Stensson; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del TransporteThis article discusses some mechanical problems which occur by using hub-motors and individual wheel steering on road vehicles. Several multi-body dynamic simulations have been done in order to illustrate the high reaction forces in the steering actuator. This paper is not about an individual steering or control per se but aims to analyse the different forces in a given steering system for different steering scenarios.Artículo The bootstrapping approach for inferring confident freight transport matrices(Fabrizio Serra editore, 2015-03) García Benítez, Francisco; Romero Pérez, Luis Miguel; Cáceres, Noelia; Castillo Granados, José María del; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Economía y Competitividad (MINECO). España; Universidad de Sevilla. TEP118: Ingeniería de los TransportesTransport studies require, as a preliminary step, conducting a survey process to a sample of the universe of users of the transportation system. The statistical reliability of the data determines the goodness of the results and conclusions that can be inferred from the analyses and models generated. In this communication a methodology, based on the techniques of "bootstrapping", to the robust statistical estimate of freight transport matrices is presented; this allows to generate the confidence intervals of travel between origin-destination pairs defined by each cell of the origin-destination matrix derived from a freight transport survey. This result is of interest in defining the dimensions of certainty for matrix cells and subsequent adjustment by techniques based on aggregate data (i.e. traffic counts, cordon line matrices, paths, etc.). The techniques of "bootstrapping" originated in the 70's, although widely used during the 90's, have not been fully exploited in the field of freight transport studies. To address this study a data set from a statistically reliable freight transport study conducted in Spain at the level of multi-province regions has been used.Artículo Alloy exsolution in co-doped PrBaMn₂₋ₓTMₓO₅+δ (TM = Co and/or Ni) obtained by mechanochemistry(Elsevier, 2024-12) Gotor Martínez, Francisco José; Sayagués de Vega, María Jesús; Zamudio-García, Javier; Marrero López, David; García-García, Francisco J.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; European Commission. Fondo Social Europeo (FSO); Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los MaterialesDoped- PrBaMn₂₋ₓTMₓO₅+δ samples with TM = Co and/or Ni were synthesized by a mechanochemical route from stoichiometric oxide precursor mixtures (Pr₆O₁₁, BaO₂, MnO, NiO and CoO) using a planetary mill at 600 rpm for 150 min. A disordered ABO₃ pseudocubic perovskite phase was obtained after the milling process that was transformed, as established by XRD, into the double layered AA’B₂O₅+δ perovskite phase after annealing at 900 ◦C in a reducing atmosphere (10%H₂/Ar). The microstructural characterization by SEM, TEM, and HRTEM ascertained that this reducing treatment induced the exsolution of Ni and Co metallic nanoparticles from the doped samples. Ni-Co alloys were even exsolved when the layered manganite phase was co-doped with both transition metals. It was confirmed that the exsolution process was reversible by switching the working atmosphere from reducing to oxidizing. Polarization resistance values of the doped samples determined in symmetrical cells in air and H₂, as well as the electrochemical performance of electrolyte LSGM-supported planar cells suggested that these samples can be used as symmetrical electrodes in SOFCs.Artículo Exploring strengths and weaknesses of mobility inference from mobile phone data vs. travel surveys(Taylor & Francis, 2020-01) Cáceres, Noelia; Romero Pérez, Luis Miguel; García Benítez, Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía; Programa Torres Quevedo (PTQ); Universidad de Sevilla. TEP118: Ingeniería de los TransportesOrigin–destination (OD) matrices serve as a basis for travel demand modelling. Traditionally, they are derived from travel surveys that collect detailed trip information but with several shortcomings. Mobile phones are regarded as a useful source of information on people’s daily mobility. This work explores the use of mobile data in the context of mobility studies by comparing matrices derived from both types of sources over the same region. The results reveal many common features in the trip information. Moreover, although the use of mobile technology may raise questions for short trips, the huge representativeness of this technology captures the mobility in OD connections extensively regardless the area. This is crucial for non-populated areas (e.g. industrial parks or educational campuses), which constitute important mobility hotspots. Based on these findings, an applicable data fusion approach to obtain the optimum accuracy from these heterogeneous sources is presented and appliedArtículo Adjustment of Origin-Destination Matrices Based on Traffic Counts and Bootstrapping Confidence Intervals(SAGE Publications, 2013-01) García Benítez, Francisco; Romero Pérez, Luis Miguel; Cáceres, Noelia; Castillo Granados, José María del; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Obras Públicas (MOP). EspañaMobility studies require, as a preliminary step, that a survey of a sample of users of the transportation system be conducted. The statistical reliability of the data determines the goodness of the results and the conclusions that can be inferred from the analyses and models generated. Because of the high costs of collection, data are partially reused in either a disaggregated or an aggregated manner. In the first case, statistical reliability is not always guaranteed; this condition affects the results that will be derived from projections and estimates of future hypothetical scenarios. A methodology is presented: it is based on bootstrapping techniques and is used for robust statistical estimation of mobility matrices. Confidence intervals of travel between origin–destination pairs defined by each matrix cell derived from a survey are generated. The result is applicable to defining the dimensions of certainty for matrix cells and subsequent adjustment by techniques based on aggregate data (e.g., traffic counts, cordon line matrices, paths). A statistically reliable data mobility study conducted in Spain at a regional level is used. Results derived from disaggregating data at an interprovincial level are presented, along with an application to the posterior mobility matrix adjustment based on traffic count data. The study results demonstrate the potential of the methodology developed and the usefulness of the conclusions.Artículo Traffic Flow Estimation Models using Cellular Phone Data(Institute of Electrical and Electronics Engineers (IEEE), 2012-09) Cáceres, Noelia; Romero Pérez, Luis Miguel; García Benítez, Francisco; Castillo Granados, José María del; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del TransporteTraffic volume is a parameter used to quantify demand in transportation studies, and it is commonly collected by using on-road (fixed) sensors such as inductive loops, cameras, etc. The installation of fixed sensors to cover all roads is neither practical nor economically feasible; therefore, they are only installed on a subset of links. Cellular phone tracking has been an emerging topic developed and investigated during the last few years to extract traffic information. Cellular systems provide alternative methods to detect phones in motion without the cost and coverage limitations associated with those infrastructure-based solutions. Utilizing existing cellular systems to capture traffic volume has a major advantage compared with other solutions, since it avoids new and expensive hardware installations of sensors, with a large number of cellular phones acting as probes. This paper proposes a set of models for inferring the number of vehicles moving from one cell to another by means of anonymous call data of phones. The models contain, in their functional form, terms related to the users’ calling behavior and other characteristics of the phenomenon such as hourly intensity in calls and vehicles. A set of intercell boundaries with different traffic background and characteristics were selected for the field test. The experiment results show that reasonable estimates are achieved by comparison with volume measurements collected by detectors located in the same study area. The motion of phones while being involved in calls can be used as an easily accessible, fast, and low-cost alternative to deriving volume data on intercell boundariesArtículo Traffic flow continuum modeling by hypersingular boundary integral equations(John Wiley & Sons, 2010-04) Romero Pérez, Luis Miguel; García Benítez, Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del TransporteThe quantity of data necessary in order to study traffic in dense urban areas through a traffic network, and the large volume of information that is provided as a result, causes managerial difficulties for the said model. A study of this kind is expensive and complex, with many sources of error connected to each step carried out. A simplification like the continuous medium is a reasonable approximation and, for certain dimensions of the actual problem, may be an alternative to be kept in mind. The hypotheses of the continuous model introduce errors comparable to those associated with geometric inaccuracies in the transport network, with the grouping of hundreds of streets in one same type of link and therefore having the same functional characteristics, with the centralization of all journey departure points and destinations in discrete centroids and with the uncertainty produced by a huge origin/destination matrix that is quickly phased out, etc. In the course of this work, a new model for characterizing traffic in dense network cities as a continuous medium, the diffusion–advection model, is put forward. The model is approached by means of the boundary element method, which has the fundamental characteristic of only requiring the contour of the problem to be discretized, thereby reducing the complexity and need for information into one order versus other more widespread methods, such as finite differences and the finite element method. On the other hand, the boundary elements method tends to give a more complex mathematical formulation. In order to validate the proposed technique, three examples in their fullest form are resolved with a known analytic solution. Copyright © 2009 John Wiley & Sons, Ltd.Artículo A boundary element numerical scheme for the two-dimensional convection–diffusion equation(John Wiley & Sons, 2008-12) Romero Pérez, Luis Miguel; García Benítez, Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del TransporteIn this study, the theoretical and numerical fundamentals of BIEM techniques for the two-dimensionalconvection–diffusion problem are presented. After an extended presentation of the basic integral formu-lation, the discretizing and iterative processes for its resolution are introduced. Interesting remarks ongeneral expressions versus previously published particularized results are worth mentioning. A numericalsolution scheme is provided, which has been completely developed and designed to the physical problemposed. A novel scheme based in the simultaneous solving of the potential and the gradient of the potentialboundary integral equations is included. A diversity of problems is tested to prove the possibilities of themethod.Artículo Estimating traffic volumes on intercity road locations using roadway attributes, socioeconomic features and other work-related activity characteristics(Springer, 2018-09) Cáceres, Noelia; Romero Pérez, Luis Miguel; Morales Sánchez, Francisco José; Reyes Gutiérrez, Antonio; García Benítez, Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España; Programa Torres Quevedo (PTQ); Universidad de Sevilla. TEP118: Ingeniería de los TransportesTraffic volume data are key inputs to many applications in highway design and planning. But these data are collected in only a limited number of road locations due to the cost involved. This paper presents an approach for estimating daily and hourly traffic volumes on intercity road locations combining clustering and regression modelling techniques. With the aim of applying the procedure to any road location, it proposes the use of roadway attributes and socioeconomic characteristics of nearby cities as explanatory variables, together with a set of previously discovered patterns with the hourly traffic percent distribution. Test results show that the proposed approach significantly produces accurate estimates of daily volumes for most locations. The accuracy at hourly level is a bit more reduced but, for periods when traffic is significant, more than half of the estimates are within 20% of absolute percentage error. Moreover, the main peak period is approximately identified for most cases. These findings together with its great applicability make this approach attractive for planners when no traffic data are available and an estimate is helpful.