A simulation model for public bike-sharing systems

Urban areas are in need of efficient and sustainable mobility services. Public bicycle sharing systems stand out as a promising alternative and many cities have invested in their deployment. This has led to a continuous and fast implementation of these systems around the world, while at the same time, research works devoted to understand the system dynamics and deriving optimal designs are being developed. In spite of this, many promoting agencies have faced the impossibility of evaluating a system design in advance, increasing the uncertainty on its performance and the risks of failure. This paper describes the development of an agent-based simulation model to emulate a bike-sharing system. The goal is to obtain a tool to evaluate and compare different alternatives for the system design before their implementation. This tool will support the decision-making process in all the stages of implementation, from the strategical planning to the daily operation. The main behavioral patterns and schemes for all agents involved are designed and implemented into a Matlab programming code. The model is validated against real data compiled from the Barcelona’s Bicing system showing good accuracy.Postprint (published version

Electric field effects on magnetotransport properties of multiferroic Py/YMnO3/Pt heterostructures

We report on the exchange bias between antiferromagnetic and ferroelectric hexagonal YMnO3 epitaxial thin films sandwiched between a metallic electrode (Pt) and a soft ferromagnetic layer (Py). Anisotropic magnetoresistance measurements are performed to monitor the presence of an exchange bias field. When the heteroestructure is biased by an electric field, it turns out that the exchange bias field is suppressed. We discuss the dependence of the observed effect on the amplitude and polarity of the electric field. Particular attention is devoted to the role of current leakage across the ferroelectric layer.Comment: Accepted for publication in Philosophical Magazine Letters (Special issue on multiferroics

High-energy radiation from T Tauri stars

T Tauri stars are young, low mass, pre-main sequence stars surrounded by an accretion disk. These objects present strong magnetic activity and powerful magnetic reconnection events. Strong shocks are likely produced in the stellar magnetosphere by such events and charged particles accelerated up to relativistic energies. We present a simple model for the non-thermal radiation generated by high-energy particles in T Tauri stars. We discuss whether this emission is detectable at high energies with the available gamma-ray telescopes.Comment: 6 pages, 6 figures, 25th Texas Symposium on Relativistic Astrophysics - TEXAS 201

The thermodynamics of creating correlations: Limitations and optimal protocols

We establish a rigorous connection between fundamental resource theories at the quantum scale. Correlations and entanglement constitute indispensable resources for numerous quantum information tasks. However, their establishment comes at the cost of energy, the resource of thermodynamics, and is limited by the initial entropy. Here, the optimal conversion of energy into correlations is investigated. Assuming the presence of a thermal bath, we establish general bounds for arbitrary systems and construct a protocol saturating them. The amount of correlations, quantified by the mutual information, can increase at most linearly with the available energy, and we determine where the linear regime breaks down. We further consider the generation of genuine quantum correlations, focusing on the fundamental constituents of our universe: fermions and bosons. For fermionic modes, we find the optimal entangling protocol. For bosonic modes, we show that while Gaussian operations can be outperformed in creating entanglement, their performance is optimal for high energies.Comment: 12 pages, 6 figure

Aplicación en la docencia posgrado de algoritmos heurísticos en la optimización de estructuras: Muros nervados

Esta comunicación presenta un curso de posgrado perteneciente al Máster Universitario en Ingeniería del Hormigón de la Universitat Politècnica de València dedicado a la formación en ingeniería. La materia se centra en el diseño automatizado de estructuras de hormigón cuyo objetivo pretende la optimización del coste de ejecución. El curso considera la mayoría de los algoritmos heurísticos básicos aplicándolos al diseño práctico de estructuras, tales como muros, pórticos y marcos de pasos inferiores de carreteras, pórticos de edificación, bóvedas, pilas, estribos y tableros de puentes. Se presenta el caso de estudio de la tipología de muro nervado de hormigón armado ejecutado in situ, usado comúnmente en la obra pública de carreteras. Se aplica el algoritmo recocido simulado (SA) a un muro de 10,00 m de altura. El modelo consta de 32 variables que definen la geometría estructural así como las características del hormigón y los armados. Se consideran varios conjuntos de parámetros para definir la heurística y cómo influyen éstos en la obtención de resultados. Finalmente, se concluye que la optimización heurística es una buena herramienta para diseñar muros reduciendo costes y que la elección de los parámetros que definen los algoritmos es fundamental para conseguir una robustez en los resultados