High Speed lines in front of conventional lines. Adaptation of conventional lines to High Speed

Análisis de las diferencias entre las líneas convencionales y las de Alta Velocidad desde el punto de vista del diseño de la infraestructura, construcción y explotación. Descripción de las soluciones por las que una línea convencional puede adaptarse a velocidades altas

Polymer Optical Fiber Plantar Pressure Sensors: Design and Validation

The proper measurement of plantar pressure during gait is critical for the clinical diagnosis of foot problems. Force platforms and wearable devices have been developed to study gait patterns during walking or running. However, these devices are often expensive, cumbersome, or have boundary constraints that limit the participant’s motions. Recent advancements in the quality of plastic optical fiber (POF) have made it possible to manufacture a low-cost bend sensor with a novel design for use in plantar pressure monitoring. An intensity-based POF bend sensor is not only lightweight, non-invasive, and easy to construct, but it also produces a signal that requires almost no processing. In this work, we have designed, fabricated, and characterized a novel intensity POF sensor to detect the force applied by the human foot and measure the gait pattern. The sensors were put through a series of dynamic and static tests to determine their measurement range, sensitivity, and linearity, and their response was compared to that of two different commercial force sensors, including piezo resistive sensors and a clinical force platform. The results suggest that this novel POF bend sensor can be used in a wide range of applications, given its low cost and non-invasive nature. Feedback walking monitoring for ulcer prevention or sports performance could be just one of those applications.This research was partially funded by Research and Innovation Programme from Community of Madrid SINFOTON2-CM (S2018/NMT-4326), and by FSE/FEDER funds, Spanish Research Agency under grant RTI2018-094669-B-C32, Spanish Ministry of Innovation and Universities under grant FJCI-2017-31677

Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions

[EN] Featured Application This work contributes to the understanding of the macroscopic characteristics of the spray as well as to the evolution of the combustion process for alternative fuels. All these fuels have been studied under the same operating conditions than diesel therefore the comparison can be made directly, leaving in evidence that some fuels can achieve a similar behavior to diesel in terms of auto ignition but avoiding one of the biggest disadvantages of diesel such as the soot formation. Moreover, the quantification of characteristic parameters such as ignition delay, liquid length, vapor penetration and flame lift-off length represent the most important data to adjust and subsequently validate the computational models that simulate the spray evolution and combustion development of these alternative fuels inside the combustion chamber. The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH* chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME(1)and a blend of oxymethylene ethers, identified as OMEx) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OME(x)sprays have similar behavior in terms of global combustion metrics. In the case of OME1, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME(1)and OME(x)was below the detection threshold in all tested conditions.This research has been partly funded by the European Union's Horizon 2020 Programme through the ENERXICO project, grant agreement no 828947, and from the Mexican Department of Energy, CONACYT-SENER Hidrocarburos grant agreement no B-S-69926 and by Universitat Politecnica de Valencia through the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-18).Pastor, JV.; García-Oliver, JM.; Mico Reche, C.; Garcia-Carrero, AA.; Gómez, A. (2020). Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions. Applied Sciences. 10(16):1-20. https://doi.org/10.3390/app10165460S1201016Reşitoğlu, İ. A., Altinişik, K., & Keskin, A. (2014). The pollutant emissions from diesel-engine vehicles and exhaust aftertreatment systems. Clean Technologies and Environmental Policy, 17(1), 15-27. doi:10.1007/s10098-014-0793-9Mohan, B., Yang, W., & Chou, S. kiang. (2013). Fuel injection strategies for performance improvement and emissions reduction in compression ignition engines—A review. Renewable and Sustainable Energy Reviews, 28, 664-676. doi:10.1016/j.rser.2013.08.051Leach, F., Kalghatgi, G., Stone, R., & Miles, P. (2020). The scope for improving the efficiency and environmental impact of internal combustion engines. Transportation Engineering, 1, 100005. doi:10.1016/j.treng.2020.100005Kim, H., Ge, J., & Choi, N. (2018). Application of Palm Oil Biodiesel Blends under Idle Operating Conditions in a Common-Rail Direct-Injection Diesel Engine. Applied Sciences, 8(12), 2665. doi:10.3390/app8122665Tziourtzioumis, D., & Stamatelos, A. (2017). Experimental Investigation of the Effect of Biodiesel Blends on a DI Diesel Engine’s Injection and Combustion. Energies, 10(7), 970. doi:10.3390/en10070970Merola, S. S., Tornatore, C., Iannuzzi, S. E., Marchitto, L., & Valentino, G. (2014). Combustion process investigation in a high speed diesel engine fuelled with n-butanol diesel blend by conventional methods and optical diagnostics. Renewable Energy, 64, 225-237. doi:10.1016/j.renene.2013.11.017Choi, K., Park, S., Roh, H. G., & Lee, C. S. (2019). Combustion and Emission Reduction Characteristics of GTL-Biodiesel Fuel in a Single-Cylinder Diesel Engine. Energies, 12(11), 2201. doi:10.3390/en12112201Dimitriadis, A., Seljak, T., Vihar, R., Žvar Baškovič, U., Dimaratos, A., Bezergianni, S., … Katrašnik, T. (2020). Improving PM-NOx trade-off with paraffinic fuels: A study towards diesel engine optimization with HVO. Fuel, 265, 116921. doi:10.1016/j.fuel.2019.116921Pastor, J. V., García, A., Micó, C., & Lewiski, F. (2020). An optical investigation of Fischer-Tropsch diesel and Oxymethylene dimethyl ether impact on combustion process for CI engines. Applied Energy, 260, 114238. doi:10.1016/j.apenergy.2019.114238Bergthorson, J. M., & Thomson, M. J. (2015). A review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines. Renewable and Sustainable Energy Reviews, 42, 1393-1417. doi:10.1016/j.rser.2014.10.034Yehliu, K., Boehman, A. L., & Armas, O. (2010). Emissions from different alternative diesel fuels operating with single and split fuel injection. Fuel, 89(2), 423-437. doi:10.1016/j.fuel.2009.08.025Gómez, A., Soriano, J. A., & Armas, O. (2016). Evaluation of sooting tendency of different oxygenated and paraffinic fuels blended with diesel fuel. Fuel, 184, 536-543. doi:10.1016/j.fuel.2016.07.049Benajes, J., García, A., Monsalve-Serrano, J., & Martínez-Boggio, S. (2020). Potential of using OMEx as substitute of diesel in the dual-fuel combustion mode to reduce the global CO2 emissions. Transportation Engineering, 1, 100001. doi:10.1016/j.treng.2020.01.001Burger, J., Siegert, M., Ströfer, E., & Hasse, H. (2010). Poly(oxymethylene) dimethyl ethers as components of tailored diesel fuel: Properties, synthesis and purification concepts. Fuel, 89(11), 3315-3319. doi:10.1016/j.fuel.2010.05.014Iannuzzi, S. E., Barro, C., Boulouchos, K., & Burger, J. (2017). POMDME-diesel blends: Evaluation of performance and exhaust emissions in a single cylinder heavy-duty diesel engine. Fuel, 203, 57-67. doi:10.1016/j.fuel.2017.04.089Omari, A., Heuser, B., & Pischinger, S. (2017). Potential of oxymethylenether-diesel blends for ultra-low emission engines. Fuel, 209, 232-237. doi:10.1016/j.fuel.2017.07.107Bjørgen, K. O. P., Emberson, D. R., & Løvås, T. (2020). Combustion and soot characteristics of hydrotreated vegetable oil compression-ignited spray flames. Fuel, 266, 116942. doi:10.1016/j.fuel.2019.116942Marchitto, L., Merola, S. S., Tornatore, C., & Valentino, G. (2016). An Experimental Investigation of Alcohol/Diesel Fuel Blends on Combustion and Emissions in a Single-Cylinder Compression Ignition Engine. SAE Technical Paper Series. doi:10.4271/2016-01-0738Payri, R., Gimeno, J., Bardi, M., & Plazas, A. H. (2013). Study liquid length penetration results obtained with a direct acting piezo electric injector. Applied Energy, 106, 152-162. doi:10.1016/j.apenergy.2013.01.027Benajes, J., Payri, R., Bardi, M., & Martí-Aldaraví, P. (2013). Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector. Applied Thermal Engineering, 58(1-2), 554-563. doi:10.1016/j.applthermaleng.2013.04.044Xuan, T., Desantes, J. M., Pastor, J. V., & Garcia-Oliver, J. M. (2019). Soot temperature characterization of spray a flames by combined extinction and radiation methodology. Combustion and Flame, 204, 290-303. doi:10.1016/j.combustflame.2019.03.023Pastor, J. V., Payri, R., Garcia-Oliver, J. M., & Briceño, F. J. (2013). Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution. SAE International Journal of Engines, 6(3), 1661-1676. doi:10.4271/2013-24-0041Pastor, J. V., García, A., Micó, C., & García-Carrero, A. A. (2020). Experimental study of influence of Liquefied Petroleum Gas addition in Hydrotreated Vegetable Oil fuel on ignition delay, flame lift off length and soot emission under diesel-like conditions. Fuel, 260, 116377. doi:10.1016/j.fuel.2019.116377Reyes, M., Tinaut, F. V., Giménez, B., & Pastor, J. V. (2018). Effect of hydrogen addition on the OH* and CH* chemiluminescence emissions of premixed combustion of methane-air mixtures. International Journal of Hydrogen Energy, 43(42), 19778-19791. doi:10.1016/j.ijhydene.2018.09.005Xuan, T., Pastor, J. V., García-Oliver, J. M., García, A., He, Z., Wang, Q., & Reyes, M. (2019). In-flame soot quantification of diesel sprays under sooting/non-sooting critical conditions in an optical engine. Applied Thermal Engineering, 149, 1-10. doi:10.1016/j.applthermaleng.2018.11.112Choi, M. Y., Mulholland, G. W., Hamins, A., & Kashiwagi, T. (1995). Comparisons of the soot volume fraction using gravimetric and light extinction techniques. Combustion and Flame, 102(1-2), 161-169. doi:10.1016/0010-2180(94)00282-wLi, D., He, Z., Xuan, T., Zhong, W., Cao, J., Wang, Q., & Wang, P. (2017). Simultaneous capture of liquid length of spray and flame lift-off length for second-generation biodiesel/diesel blended fuel in a constant volume combustion chamber. Fuel, 189, 260-269. doi:10.1016/j.fuel.2016.10.058Lequien, G., Berrocal, E., Gallo, Y., Themudo e Mello, A., Andersson, O., & Johansson, B. (2013). Effect of Jet-Jet Interactions on the Liquid Fuel Penetration in an Optical Heavy-Duty DI Diesel Engine. SAE Technical Paper Series. doi:10.4271/2013-01-1615Kook, S., & Pickett, L. M. 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Helical surface magnetization in nanowires: the role of chirality

Nanomagnetism is nowadays expanding into three dimensions, triggered by the discovery of new magnetic phenomena and their potential use in applications. This shift towards 3D structures should be accompanied by strategies and methodologies to map the tridimensional spin textures associated. We present here a combination of dichroic X-ray transmission microscopy at different angles and micromagnetic simulations allowing to determine the magnetic configuration of cylindrical nanowires. We have applied it to permalloy nanowires with equispaced chemical barriers that can act as pinning sites for domain walls. The magnetization at the core is longitudinal and generates at the surface of the wire helical magnetization. Different types of domain walls are found at the pinning sites, which respond differently to applied fields depending on the relative chirality of the adjacent domains

Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single- crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity. Published by AIP Publishing

Magnetic domains on magnetite islands: from XMCD-PEEM to micromagnetism

Oral presentation given at the 13th European Conference on Surface Crystallography and Dynamics, held in Donostia-San Sebastián, Spain, on June 19-21th, 2017.Magnetite nanostructures and thin films have been grown in spintronic devices such as spin valves in order to take advantage of the high Curie temperature, stability, and predicted half-metal character. However, thin films present magnetic properties which are rather different from the properties of bulk magnetite: high coercive fields, high saturation fields, out-of-plane magnetization, superparamagnetism in ultrathin films, or unexpected easy-axes. An explanation for these effects are growth defects, among which antiphase domain boundaries (APBs) are the best example. In the present work, we study the magnetic domains on flat single-crystal magnetite and other mixed spinels grown on Ru(0001) by molecular beam epitaxy [1,2]. As each island grows from a single nucleus, there are expected to be free of APBs. We have measured with nanometer-resolution the 3D magnetization of the islands by combining x-ray magnetic circular dichroism images acquired in a photoemission electron microscope at different azimuthal angles. The 3D magnetization maps have been used as the initial magnetization configuration for micromagnetic simulations of islands with the same lateral and vertical dimensions as the experimental ones. The Mumax3 software has been used to perform the micromagnetic simulations. By comparing the evolution of the micromagnetic simulations with the experimental behavior of the islands after annealing, we seek to validate the material parameters that define their magnetic behavior and to identify cases where defects or other effects play a role

Large spin-mixing conductance in highly Bi-doped Cu thin films

Spin Hall effect provides an efficient tool for the conversion of a charge current into a spin current, opening the possibility of producing pure spin currents in non-magnetic materials for the next generation of spintronics devices. In this sense, giant Spin Hall Effect has been recently reported in Cu doped with 0.5 % Bi grown by sputtering and larger values are expected for larger Bi doping, according to first principles calculations. In this work we demonstrate the possibility of doping Cu with up to 10 % of Bi atoms without evidences of Bi surface segregation or cluster formation, as studied by different microscopic and spectroscopic techniques. In addition, YIG/BiCu structures have been grown, showing a spin mixing conductance larger that the one shown by similar Pt/YIG structures. These results reflects the potentiality of these new materials in spintronics devices.Comment: 6 pages, 4 figure

Highly Bi-doped Cu thin films with large spin-mixing conductance

The spin Hall effect (SHE) provides an efficient tool for the production of pure spin currents, essentially for the next generation of spintronics devices. Giant SHE has been reported in Cu doped with 0.5% Bi grown by sputtering, and larger values are predicted for larger Bi doping. In this work, we demonstrate the possibility of doping Cu with up to 10% of Bi atoms without evidence of Bi surface segregation or cluster formation. In addition, YIG/BiCu structures have been grown, showing a spin mixing conductance larger that the one shown by similar Pt/YIG structures, reflecting the potentiality of these newmaterials

Observation of a topologically protected state in a magnetic domain wall stabilized by a ferromagnetic chemical barrier

The precise control and stabilization of magnetic domain walls is key for the development of the next generation magnetic nano-devices. Among the multitude of magnetic configurations of a magnetic domain wall, topologically protected states are of particular interest due to their intrinsic stability. In this work, using XMCD-PEEM, we have observed a topologically protected magnetic domain wall in a ferromagnetic cylindrical nanowire. Its structure is stabilized by periodic sharp alterations of the chemical composition in the nanowire. The large stability of this topologically protected domain wall contrasts with the mobility of other non-protected and non-chiral states also present in the same nanowire. The micromagnetic simulations show the structure and the conditions required to find the topologically protected state. These results are relevant for the design of future spintronic devices such as domain wall based RF oscillators or magnetic memories

Desarrollo de herramientas para el aprendizaje interactivo y experimental del Electromagnetismo en el aula

Depto. de Física de MaterialesFac. de Ciencias FísicasFALSEsubmitte