Effect of Co and Fe on the inverse magnetocaloric properties of Ni-Mn-Sn

At certain compositions Ni-Mn-$X$ Heusler alloys ($X$: group IIIA-VA elements) undergo martensitic transformations, and many of them exhibit inverse magnetocaloric effects. In alloys where $X$ is Sn, the isothermal entropy change is largest among the Heusler alloys, particularly in Ni$_{50}$Mn$_{37}$Sn$_{13}$ where it reaches a value of 20 Jkg$^{-1}$K$^{-1}$ for a field of 5T. We substitute Ni with Fe and Co in this alloy, each in amounts of 1 at% and 3 at% to perturb the electronic concentration and examine the resulting changes in the magnetocaloric properties. Increasing both Fe and Co concentrations causes the martensitic transition temperature to decrease, whereby the substitution by Co at both compositions or substituting 1 at% Fe leads to a decrease in the magnetocaloric effect. On the other hand, the magnetocaloric effect in the alloy with 3 at% Fe leads to an increase in the value of the entropy change to about 30 Jkg$^{-1}$K$^{-1}$ at 5T.Comment: 5 pages, 7 figures. Accepted for publication in the Journal of Applied Physic

Ingeniería inversa del TALGO-I

I Premio para jóvenes Ingenieros Ferroviarios TRIA Railway R&D, 2011.Esta iniciativa nace de la voluntad de Talgo y Renfe por recuperar el proyecto innovador del Talgo I, ideado por el Sr. Alejandro Goicoechea Omar. Actualmente, apenas se conservan documentos sobre el >, nombre por el que era conocido en la época, y cada vez son menos los testimonios a los que consultar. Algunas fotografías y artículos son el único material de archivo existente sobre un proyecto que revolucionó la historia del ferrocarril e hizo evolucionar al tren hasta llegar al que conocemos hoy en día. En base a la poca información existente, y a partir de una ingeniería inversa sobre el Talgo I, se ha diseñado pieza a pieza todo el conjunto de cada uno de los cuatro vagones, a partir de técnicas de dibujo como la perspectiva cónica aplicada a las imágenes existentes y las medidas conocidas de los vagones. Ya modelada cada pieza por separado, se ha hecho un estudio para comprobar si las geometrías aplicadas eran correctas dependiendo de si en la época se hubieran podido fabricar y con qué se habrían construido. Una vez obtenido el diseño final, se ha estudiado su posible proceso de fabricación para un correcto montaje. Cabe que destacar que se han tenido en cuenta las técnicas y recursos de la época en que fue construido el Talgo I. Con todas las estructuras modeladas en tres dimensiones, con CATIA V5R18, se ha puesto a prueba su resistencia mediante el módulo de simulación de elementos finitos (FEM), primero con el peso único del vagón, y seguidamente añadiendo el peso de los viajeros. En las simulaciones se ha podido observar como la estructura con el simple peso del vagón estaba al borde del colapso, ya que las tensiones de Von Mises se acercaban al límite elástico del material utilizado (AISI 1015). Al añadir el peso de los viajeros las tensiones han sobrepasado el límite elástico. Por lo tanto, como solución se ha propuesto una mejora básica para optimizar el diseño creado. Por último se ha acotado cada parte de los cuatro vagones modelados para poder dejar constancia de las dimensiones aproximadas obtenidas.Award-winnin

Winning spaces : participatory methodologies in rural processes in Mexico

This study examines the development and impact of participatory methodologies (PMs) in Mexico, and forms part of the wider research programme Pathways to Participation. The material for this paper was gathered from interviews and workshops with practitioners of PMs across Mexico, and includes three case studies drawn from contrasting initiatives promoted by organisations as disparate as research institutes, state and federal government, and the World Bank. Mexico has a strong and distinctive participatory tradition stretching back to the 1960s, when currents of thought such as liberation theology and Freireian concientización, predating the arrival of Participatory Rural Appraisal (PRA) in the region, were influential in the development of endogenous PMs. The Mexican version of PRA and other PMs are thus different to those which have been introduced from Anglo Saxon cultures: in Mexican versions, there is greater emphasis on increasing the capacity for critical analysis and personal and social consciousness. These differences are found to contribute to the flexibility and adaptability of PMs and their potential to generate social action and transformation. Generally, PMs and particularly PRA are found to have theoretical and methodological weaknesses in the Mexican context, in relation to knowledge and respect for rural reality and practices, and recognition of opportunities for its transformation. The study suggests a need to adapt these methods to the political context of conflict and socio-cultural diversity, and to address the challenge of developing an ethical code for implementing participatory processes, and of how to scale up and deepen the achievements of each intervention in the countryside. PRA has been adopted and modified by many practitioners to suit the local context, but the challenge of this modified PRA continues to be finding a balance between respect for the practice, knowledge and institutions of a community, and the use of educational methods that question and challenge injustices in the established order

Magnetization easy-axis in martensitic Heusler alloys estimated by strain measurements under magnetic-field

We study the temperature dependence of strain under constant magnetic-fields in Ni-Mn based ferromagnetic Heusler alloys in the form Ni-Mn-$X$ ($X$: Ga, In, Sn, Sb) which undergo a martensitic transformation. We discuss the influence of the applied magnetic-field on the nucleation of ferromagnetic martensite and extract information on the easy-axis of magnetization in the martensitic state.Comment: 3 pages, 3 figures. Accepted for publication in Applied Physics Letter

High-contrast imaging of 180{\deg} ferroelectric domains by optical microscopy using ferroelectric liquid crystals

Ferroelectric liquid crystals (FLCs) couple the direction of their spontaneous electric polarization to the direction of tilt of their optic axis. Consequently, reversal of the electric polarization by an electric field gives rise to an immediate and lasting optical response when an appropriately aligned FLC is observed between crossed polarizers, with one field direction yielding a dark image, and the opposite direction yielding a bright image. Here this peculiar electro-optic response is used to image, with high optical contrast, 180{\deg} ferroelectric domains in a crystalline substrate of magnesium-doped lithium niobate. The lithium niobate substrate contains a few domains with upwards electric polarization surrounded by regions with downward electric polarization. In contrast to a reference non-chiral liquid crystal that is unable to show ferroelectric behavior due to its high symmetry, the FLC, which is used as a thin film confined between the lithium niobate substrate and an inert aligning substrate, reveals ferroelectric domains as well as their boundaries, with strong black and white contrast. The results show that FLCs can be used for non-destructive read-out of domains in underlying ferroelectrics, with potential applications in e.g. photonic devices and non-volatile ferroelectric memories.Comment: 12 pages, 3 figure

Effects of hydrostatic pressure on the magnetism and martensitic transition of Ni-Mn-In magnetic superelastic alloys

We report magnetization and differential thermal analysis measurements as a function of pressure accross the martensitic transition in magnetically superelastic Ni-Mn-In alloys. It is found that the properties of the martensitic transformation are significantly affected by the application of pressure. All transition temperatures shift to higher values with increasing pressure. The largest rate of temperature shift with pressure has been found for Ni$_{50}$Mn$_{34}$In$_{16}$ as a consequence of its small entropy change at the transition. Such a strong pressure dependence of the transition temperature opens up the possibility of inducing the martensitic transition by applying relatively low hydrostatic pressures.Comment: 3 pages, 3 figures. Accepted for publication in Applied Physics Letter

Strategic Deployment of Swarm of UAVs for Secure IoT Networks

Security provisioning for low-complex and constrained devices in the Internet of Things (IoT) is exacerbating the concerns for the design of future wireless networks. To unveil the full potential of the sixth generation (6G), it is becoming even more evident that security measurements should be considered at all layers of the network. This work aims to contribute in this direction by investigating the employment of unmanned aerial vehicles (UAVs) for providing secure transmissions in ground IoT networks. Toward this purpose, it is considered that a set of UAVs acting as aerial base stations provide secure connectivity between the network and multiple ground nodes. Then, the association of IoT nodes, the 3D positioning of the UAVs and the power allocation of the UAVs are obtained by leveraging game theoretic and convex optimization-based tools with the goal of improving the secrecy of the system. It is shown that the proposed framework obtains better and more efficient secrecy performance over an IoT network than state-of-the-art greedy algorithms for positioning and association

EGA- Reconstrucció. Arquitectures i paisatges. Grans mestres de l'arquitectura valenciana. F.M.Barberá. La reconstrucció gràfica del patrimoni perdut. Escola d'Agrònoms.

[ES] El presente estudio nace como homenaje al arquitecto Fernando Moreno Barberá tras la demolición de parte de uno de sus edificios, de esta forma, pretendemos exaltar la figura del mismo creando un espacio de protección a su obra. Para ello, se revisa la trayectoria del maestro, analizando su obra respecto al momento concreto de su construcción y sus referencias, así como la concreción de los mecanismos compositivos y sus formas, que dentro de la idea abstracta que emplea el movimiento moderno, son personales y se acercan a lo local mirando muy concretamente a su entorno. La obra de Moreno Barberá es clave dentro de la arquitectura moderna en la España del siglo XX, especialmente por sus proyectos docentes hasta los años setenta, entre los cuales encontramos la Escuela de Ingenieros Agrónomos junto con la Escuela de Peritos Técnicos Agrónomos en el que se centrará este trabajo con una reconstrucción gráfica. La escuela de Peritos Técnicos Agrónomos de Valencia se trata de un inmueble que fue dejado de usar para su fin en el 2010 y que durante este tiempo ha estado abandonado hasta parte de su demolición en 2020.[EN] This study was born as a tribute to the architect Fernando Moreno Barberá after the demolition of part of one of his buildings, in this way, we try to exalt his figure at the sorne time that we hove created a space of protection to his work. To do this, the trajectory of the master is reviewed, analyzing his work at the specific time of its construction and its references, as well as the compositional mechanisms and its forms, which within the abstract idea used by the modern movement, are personal and approach the local looking and the building environment. Moreno Barberá's work is key to modern architecture in twentieth century Spain, especially for his educational projects until the seventies, among which we find the School of Agricultura! Engineers together with the School of Agricultura! Technical Experts on which this work will focus with a graphic reconstruction. The School of Agricultura! Technicians of Valencia is a building that was abandoned for its purpose in 2010 and during this time has been abandoned until part of its demolition in 2020.Moya Godoy, X. (2022). EGA- Reconstrucción. Arquitecturas y paisajes. Grandes maestros de la arquitectura valenciana. F. M. Barberá. La reconstrucción gráfica del patrimonio perdido. Escuela de Agrónomos. Universitat Politècnica de València. http://hdl.handle.net/10251/19047