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A Comparative Analysis of Global Mobile Network Aggregators
No full textThe mobile telecommunication industry is undergoing continuous evolution to cope with ever increasing service requirements and expectations of end users. This has recently led to the rise of Mobile Network Aggregators (MNAs), a new type of global virtual operators that deliver mobile communication services by utilizing multiple Mobile Network Operators (MNOs), dynamically connecting to the one that best meets their customers’ needs based on location and time. MNAs can then offer optimized global coverage by connecting to local MNOs that have limited (e.g., national) geographic service. In this paper, we provide a first in-depth analysis of the operations of three major MNAs: Google Fi, Twilio, and Truphone. We conduct performance measurements across these MNAs for critical applications spanning DNS, Web browsing, and video streaming, and compare their performance against that of a traditional MNO from two very diverse geographical locations, US and Spain. We find that MNAs may introduce some delay compared to local MNOs in the region where the user is roaming, yet they offer significant performance improvements over the traditional MNOs roaming model, such as home-routed roaming. To fully assess the potential benefits of the MNA model, we also carry out emulation studies assessing the potential performance gains that MNAs could achieve by deploying both control and user plane functions of open-source 5G implementations across different Amazon Web Services locations.This work has been partially supported by the ORIGAMI project, which has received funding from the Smart Networks and Services Joint Undertaking (SNS JU) under the European Union’s Horizon Europe research and innovation programme with Grant Agreement No. 101139270. The work of Marcelo Bagnulo has been partially funded by the EU through the StandICT RXQ project
Isospectral graphs via spectral bracketing
No full textIn this article, we develop a perturbative technique to construct families of non-isomorphic discrete graphs which are isospectral for the standard (also called normalised) Laplacian and its signless version. We use vertex contractions as a graph perturbation and spectral bracketing with auxiliary graphs which have certain eigenvalues with high multiplicity. There is no need to know explicitly the eigenvalues or eigenfunctions of the corresponding graphs. We illustrate the method by presenting several families of examples of isospectral graphs including fuzzy complete bipartite graphs and subdivision graphs obtained from the previous examples. All the examples constructed turn out to be also isospectral for the standard (Kirchhoff) Laplacian on the associated equilateral metric graph.JSFC was supported by the Leverhulme Trust via a Research Project Grant (RPG-2020-158). FLl was supported by the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0554) and from the Spanish National Research Council, through the Ayuda extraordinaria a Centros de Excelencia Severo Ochoa (20205CEX001) and by the Madrid Government under the Agreement with UC3M in the line of Research Funds for Beatriz Galindo Fellowships (C&QIG-BG-CM-UC3M), and in the context of the V PRICI
Zero-Free Regions of the Riemann Zeta Function and Approximation in Weighted Dirichlet Spaces
No full textWe study zero-free regions of the Riemann zeta function ζ related to an approximation problem in the weighted Dirichlet space D−2 which is known to be equivalent to the Riemann Hypothesis since the work of Báez-Duarte. We prove, indeed, that analogous approximation problems for the standard weighted Dirichlet spaces Dα (...)Eva A. Gallardo-Gutiérrez is partially supported by Plan Nacional I+D grants no. PID2019-106433GB-I00 and PID2022-137294NB-I00, Spain, the Spanish Ministry of Science and Innovation, through the “Severo Ochoa Programme for Centres of Excellence in R&D” (CEX2019-000904-S & CEX2023- 001347) and from the Spanish National Research Council, through the “Ayuda extraordinaria a Centros de Excelencia Severo Ochoa” (20205CEX001). Daniel Seco is funded by the Spanish Ministry of Science and Innovation through the Plan Nacional grant PID2019-105979GB-I00, by the Ramón y Cajal programme from Agencia Estatal de Investigación through grant RYC2021-034744-I, and by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M23), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation)
Gestión adaptativa del tráfico urbano mediante agentes BDI inteligentes
No full textEste Trabajo de Fin de Grado tiene como objetivo el desarrollo de un simulador de tráfico urbano que emula el comportamiento de vehículos y semáforos mediante el uso de agentes inteligentes. La arquitectura seleccionada para la simulación es la BDI (Belief-Desire-Intention), que permite a los agentes razonar y adaptarse a su entorno, lo que resulta en un sistema más flexible y eficiente en comparación con las soluciones estáticas tradicionales.
Después de una investigación extensiva sobre estos agentes y sus arquitecturas, se ha procedido a desarrollar un diseño para el problema en cuestión.
Los agentes en el sistema representan tanto a los vehículos como a los semáforos y otros elementos del entorno (sensores, señales de tráfico, etc.), y son capaces de comunicarse entre sí, tomar decisiones y adaptarse a las condiciones cambiantes del tráfico.
El diseño se centra en la creación de una ontología que defina las creencias y deseos de los agentes, así como los protocolos de interacción que permiten la comunicación entre ellos. A través de estos mecanismos, los semáforos pueden ajustar sus fases y los vehículos pueden tomar decisiones de ruta, de acuerdo con el estado del tráfico.
El simulador fue probado en varios escenarios de tráfico simulados para evaluar su rendimiento. Las pruebas se centraron en situaciones de congestión, cambios en el flujo vehicular y la respuesta de los semáforos ante estas situaciones. Las métricas utilizadas para la evaluación incluyeron los tiempos de llegada de los vehículos y la reducción de la congestión.
En resumen, este TFG propone una solución para la gestión del tráfico urbano, utilizando una arquitectura basada en agentes que se adapta dinámicamente a las condiciones cambiantes del entorno.Grado en Ingeniería Informátic
Análisis del impacto de los recursos energéticos distribuidos en sistemas eléctricos aislados con alto índice de penetración renovable
No full textComparative study of direct and indirect aqueous mineral carbonation of construction and demolition waste fines for CO2 sequestration
No full textSustainable development prioritizes waste utilization to mitigate environmental impacts through recycling and reuse. In construction and demolition waste (C&DW) recycling, the recovery of recycled concrete aggregate generates C&DW fines. These fines contain significant calcium (Ca), making them potential feedstock for CO2 sequestration through accelerated mineral carbonation processes. This approach offers a promising pathway for reducing CO2 emissions from the cement industry by utilizing alkaline waste to form thermodynamically stable carbonates. This study compares the effectiveness of direct and indirect aqueous mineral carbonation in sequestering CO2 using classified C&DW fines. Laboratory experiments assessed Ca extraction using borehole water (BHW) and acid mine drainage (AMD) as leaching agents, along with optimization of the solid-to-liquid (S/L) ratio for carbonation. Analysis of raw C&DW fines, leached residue, leachate, and the resulting solid carbonation product was performed using XRD, XRF, TGA, BET/BJH, PSD, and ICP-OES techniques. A 1:10 S/L ratio was optimal for Ca extraction and subsequent carbonation. BHW leached ∼328 mg-Ca/L-BHW, significantly higher than AMD (85 mg-Ca/L-AMD). High concentration of SO2 4 in AMD reacted with Ca to form gypsum, limiting Ca leaching into the solution. Thus, BHW was used in subsequent carbonation experiments. Direct aqueous carbonation achieved a total CO2 uptake of 52.8 g-CO2/kg-C&DW fines, whereas indirect aqueous carbonation captured 10.5 g-CO2/kg-C&DW fines. This research highlights the benefit of repurposing C&DW as low-cost material for direct CO2 capture. Moreover, the potential substitution of BHW with polluted waste streams like AMD underscores an integrated approach to waste valorization and CO2 mitigation, particularly in water-scarce regions.This study was supported by the Science and Technology Research Partnership for Sustainable Development (SATREPS; grant number – JPMJSA2003) in collaboration between the Japan Science and Technology Agency, the Japan International Cooperation Agency, and the Department of Science and Innovation of South Africa
La Teoría Jurídica Liberal y el Debate sobre el Estado Administrativo
Get PDFPrograma de Doctorado en Derecho por la Universidad Carlos III de MadridPresidente: Tomás de la Quadra-Salcedo Fdez. del Castillo.- Secretario: Mariano Carlos Melero de la Torre.- Vocal: Isabel Lifante Vida
Performance improvement of absorption chillers: A review on nanoparticle addition
Get PDFA review on the use of nanoparticles to improve the performance of absorption chillers is presented. The review includes a compilation and discussion of research data on the subject using as base fluids NH3-H2O, H2O-LiBr and other solutions. Topics analysed include: theoretical and experimental studies about mass transfer enhancement in absorbers and desorbers; research to improve performance of complete absorption chillers; evaluation of thermophysical properties and stability of nanofluids, including viscosity, surface tension, thermal conductivity and other properties; and other studies with results useful for implementation in absorption chillers. Trends about the use of nanofluids in absorption systems, type and concentration of nanoparticles that provide the best performances and specific topics that require more research are identified from the review. Strategies are proposed for future research or for decision makers related to absorption chillers.Financed by: FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación/_Proyecto (DPI2017-83123-R)
Key influencing factors in vehicle platoons: a systematic study and review
Get PDFVehicle platooning presents a promising approach to enhancing traffic efficiency in autonomous driving. This technique offers numerous benefits, including reduced travel time, lower emissions, improved fuel efficiency, and the potential to mitigate traffic congestion. Despite the aforementioned advantages, the technology is still in its developmental stages, facing several significant technical issues. Key challenges arise from the evolving nature of the vehicle platoon, including vehicle heterogeneity, external disturbances like wind affecting longitudinal dynamics, and delays or interruptions in communication networks. For these reasons, this paper conducts a simulation-based research into the impact of various factors, such as communication delays, network disconnections, external disturbances, among others, on the string stability of vehicle platoons. The simulation results reveal that network disconnections have the most detrimental effect, as they can lead to severe string instability. Other factors, such as external disturbances, do not compromise string stability but may result in steady-state tracking errors
Estudio comparativo del rendimiento de los estándares de firma digital post-cuánticos
Get PDFLa irrupción de la computación cuántica plantea una amenaza significativa para los sistemas criptográficos actuales. En concreto, a raíz de los algoritmos de Shor y Grover, la seguridad de los sistemas de clave pública se pone en peligro. Como consecuencia, es necesario que cada vez haya más estudios acerca de posibles soluciones: investigaciones sobre esquemas criptográficos que sean resistentes a ataques con computación cuántica. Para estandarizar estos esquemas, el NIST inició en 2016 una convocatoria en la cual se estandarizaron algunos esquemas de firma. Entre ellos se encuentran CRYSTALSDilithium y SPHINCS+. Este Trabajo de Fin de Grado tiene como objetivo el análisis y la comparación de rendimiento entre tres esquemas de firma post-cuánticos: ML-DSA, el cual es derivado de CRYSTALS-Dilithium; XMSS, un esquema basado en funciones hash; y SLH-DSA, que utiliza una variante de XMSS y es derivado de SPHINCS+.
Para poder medir correctamente el rendimiento, es necesario hacer una implementación fiable de cada esquema, junto con un sistema capaz de medir todos los parámetros necesarios. Los parámetros a medir serán principalmente el tiempo de ejecución y ciclos de CPU utilizados para los tres principales procesos de un esquema de firma: generación de claves, firma de un mensaje y verificación de una firma. También se medirá el tamaño de la clave pública, de la clave privada y de las firmas. Para hacer la implementación de los tres esquemas se utiliza la librería criptográfica Botan [1], una librería de C++ de código abierto que implementa los tres esquemas que se van a estudiar en este trabajo.
Se ha realizado un análisis individual de cada esquema, evaluando cómo afectan los diferentes parámetros al rendimiento del algoritmo. Además, se ha hecho un análisis comparativo del rendimiento de los tres esquemas, para finalmente obtener conclusiones acerca de las ventajas y desventajas de cada esquema. Los resultados indican que la elección de un esquema u otro va a depender de los objetivos y requisitos que tenga la implementación.
Si se busca únicamente tiempos de ejecución rápidos, ML-DSA es la mejor opción. Por el contrario, si se necesitan tamaños de clave muy reducidos, SLH-DSA es mejor opción que el resto. Por último, en el hipotético caso de que haya una gran limitación de memoria, y se necesita minimizar tanto los tamaños de clave como los de firma, XMSS puede ser una buena elección, dependiendo de los requisitos que haya en cuanto a tiempos de ejecución.Grado en Ingeniería Informátic