356 research outputs found

    Electron Thermal Runaway in Atmospheric Electrified Gases: a microscopic approach

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    Thesis elaborated from 2018 to 2023 at the Instituto de Astrofísica de Andalucía under the supervision of Alejandro Luque (Granada, Spain) and Nikolai Lehtinen (Bergen, Norway). This thesis presents a new database of atmospheric electron-molecule collision cross sections which was published separately under the DOI : With this new database and a new super-electron management algorithm which significantly enhances high-energy electron statistics at previously unresolved ratios, the thesis explores general facets of the electron thermal runaway process relevant to atmospheric discharges under various conditions of the temperature and gas composition as can be encountered in the wake and formation of discharge channels

    Analysis, Design and Fabrication of Micromixers, Volume II

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    Micromixers are an important component in micrototal analysis systems and lab-on-a-chip platforms which are widely used for sample preparation and analysis, drug delivery, and biological and chemical synthesis. The Special Issue "Analysis, Design and Fabrication of Micromixers II" published in Micromachines covers new mechanisms, numerical and/or experimental mixing analysis, design, and fabrication of various micromixers. This reprint includes an editorial, two review papers, and eleven research papers reporting on five active and six passive micromixers. Three of the active micromixers have electrokinetic driving force, but the other two are activated by mechanical mechanism and acoustic streaming. Three studies employs non-Newtonian working fluids, one of which deals with nano-non-Newtonian fluids. Most of the cases investigated micromixer design

    Deep material networks for efficient scale-bridging in thermomechanical simulations of solids

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    We investigate deep material networks (DMN). We lay the mathematical foundation of DMNs and present a novel DMN formulation, which is characterized by a reduced number of degrees of freedom. We present a efficient solution technique for nonlinear DMNs to accelerate complex two-scale simulations with minimal computational effort. A new interpolation technique is presented enabling the consideration of fluctuating microstructure characteristics in macroscopic simulations

    Development of a wide-spectrum thermochemical code with application to planar reacting and non-reacting shocks

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    Mención Internacional en el título de doctorThe recent scientific and technological advancements have underscored the critical necessity for reliable, robust, and efficient numerical codes capable of predicting the chemical composition and properties of complex mixtures at chemical equilibrium. In response to this demand, this thesis presents the development and validation of a novel open-source thermochemical code called Combustion Toolbox (CT). This tool is designed to determine the equilibrium state of multi-species mixtures in gaseous or pure condensed phases, including ions. The code incorporates a comprehensive suite of algorithms, ranging from fundamental chemical equilibrium problems to complex computations of steady shock and detonation waves in various flow configurations, as well as predictions of rocket engine performance. Implemented in MATLAB, CT is accompanied by a user-friendly graphical user interface, ensuring flexibility and accessibility for all users. Extensive validation demonstrates excellent agreement with established codes such as NASA’s CEA, Cantera within Caltech’s Shock and Detonation Toolbox, and the recent Thermochemical Equilibrium Abundances code. CT has been utilized in all of the studies presented in this thesis, demonstrating its reliability and versatility. The second part of the thesis delves into the theoretical analysis of reactive and nonreactive shocks propagating through non-homogeneous conditions. Conducting experiments and high-fidelity simulations in this field can be challenging and computationally expensive. In this context, linear interaction analysis has emerged as a valuable tool to evaluate the hydrodynamical aspects contributing to the amplification of disturbances across the shock. Two prominent cases are investigated. Firstly, the study focuses on detonations with inhomogeneities in the upstream fuel mass fraction. The findings reveal that, in most cases, the detonation propagation speed is higher than in equivalent homogeneous scenarios. Subsequently, the investigation shifts towards the interaction of hypersonic shocks with turbulent flows, incorporating the associated thermochemical effects in single-species diatomic gases. The analysis is further extended to multi-species mixtures using CT, with a particular emphasis on air. These studies demonstrate that thermochemical effects arising at hypersonic velocities significantly enhance turbulent fluctuations in the post-shock gas compared to the simplified thermochemical frozen gas assumption.Los avances científicos y tecnológicos recientes han destacado la necesidad crítica de contar con códigos numéricos fiables, robustos y eficientes capaces de predecir la composición química y las propiedades de mezclas complejas en equilibrio químico. En respuesta a esta demanda, esta tesis presenta el desarrollo y la validación de un novedoso código termoquímico de código abierto llamado Combustion Toolbox (CT). Esta herramienta permite determinar el estado de equilibrio de mezclas multiespecie en fases gaseosas o condensadas puras, incluyendo iones. El código incorpora una amplia gama de algoritmos, desde problemas fundamentales de equilibrio químico hasta complejos cálculos de ondas de choque y detonación estacionarias en varias configuraciones de flujo, así como predicciones del rendimiento de motores cohete. Implementado en MATLAB, CT cuenta con una interfaz gráfica de usuario fácil de usar, que garantiza flexibilidad y accesibilidad para todos los usuarios. Se ha realizado una extensa validación que demuestra una excelente concordancia con códigos establecidos como el CEA de la NASA, Cantera y Shock and Detonation Toolbox del Caltech, así como el reciente código Thermochemical Equilibrium Abundances. CT se ha utilizado en todos los estudios presentados en esta tesis, demonstrando su fiabilidad y versatilidad. En la segunda parte de la tesis, se analizan los choques reactivos y no reactivos que se propagan en condiciones no homogéneas. Realizar experimentos y simulaciones de alta fidelidad en este campo puede ser desafiante y costoso computacionalmente. En este contexto, el análisis de interacción lineal ha surgido como una herramienta valiosa para evaluar los aspectos hidrodinámicos que contribuyen a la amplificación de las perturbaciones a través del choque. Se investigan dos casos destacados. En primer lugar, el estudio se centra en las detonaciones con inhomogeneidades aguas arriba de la fracción másica del combustible. Los resultados indican que, en la mayoría de los casos, la velocidad de propagación de la detonación es mayor que en escenarios homogéneos equivalentes. Posteriormente, la investigación se centra en la interacción de choques hipersónicos con flujos turbulentos, incorporando los efectos termoquímicos asociados en gases diatómicos de una sola especie. El análisis se extiende además a mezclas multiespecie utilizando CT, con un énfasis particular en el aire. Estos estudios demuestran que los efectos termoquímicos que surgen a velocidades hipersónicas aumentan significativamente las fluctuaciones turbulentas en el gas posterior al choque en comparación con la aproximación de gas termoquímicamente congelado.Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira iPresidente: Francisco José Higuera Antón.- Secretario: Carlos Manuel del Pino Peñas.- Vocal: Bruno Dene

    Modeling and Simulation in Engineering

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    The Special Issue Modeling and Simulation in Engineering, belonging to the section Engineering Mathematics of the Journal Mathematics, publishes original research papers dealing with advanced simulation and modeling techniques. The present book, “Modeling and Simulation in Engineering I, 2022”, contains 14 papers accepted after peer review by recognized specialists in the field. The papers address different topics occurring in engineering, such as ferrofluid transport in magnetic fields, non-fractal signal analysis, fractional derivatives, applications of swarm algorithms and evolutionary algorithms (genetic algorithms), inverse methods for inverse problems, numerical analysis of heat and mass transfer, numerical solutions for fractional differential equations, Kriging modelling, theory of the modelling methodology, and artificial neural networks for fault diagnosis in electric circuits. It is hoped that the papers selected for this issue will attract a significant audience in the scientific community and will further stimulate research involving modelling and simulation in mathematical physics and in engineering

    PhD students´day FMST 2023

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    The authors gave oral presentations of their work online as part of a Doctoral Students’ Day held on 15 June 2023, and they reflect the challenging work done by the students and their supervisors in the fields of metallurgy, materials engineering and management. There are 82 contributions in total, covering a range of areas – metallurgical technology, thermal engineering and fuels in industry, chemical metallurgy, nanotechnology, materials science and engineering, and industrial systems management. This represents a cross-section of the diverse topics investigated by doctoral students at the faculty, and it will provide a guide for Master’s graduates in these or similar disciplines who are interested in pursuing their scientific careers further, whether they are from the faculty here in Ostrava or engineering faculties elsewhere in the Czech Republic. The quality of the contributions varies: some are of average quality, but many reach a standard comparable with research articles published in established journals focusing on disciplines of materials technology. The diversity of topics, and in some cases the excellence of the contributions, with logical structure and clearly formulated conclusions, reflect the high standard of the doctoral programme at the faculty.Ostrav

    Roadmap for Optical Tweezers 2023

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    Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration

    The Fifteenth Marcel Grossmann Meeting

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    The three volumes of the proceedings of MG15 give a broad view of all aspects of gravitational physics and astrophysics, from mathematical issues to recent observations and experiments. The scientific program of the meeting included 40 morning plenary talks over 6 days, 5 evening popular talks and nearly 100 parallel sessions on 71 topics spread over 4 afternoons. These proceedings are a representative sample of the very many oral and poster presentations made at the meeting.Part A contains plenary and review articles and the contributions from some parallel sessions, while Parts B and C consist of those from the remaining parallel sessions. The contents range from the mathematical foundations of classical and quantum gravitational theories including recent developments in string theory, to precision tests of general relativity including progress towards the detection of gravitational waves, and from supernova cosmology to relativistic astrophysics, including topics such as gamma ray bursts, black hole physics both in our galaxy and in active galactic nuclei in other galaxies, and neutron star, pulsar and white dwarf astrophysics. Parallel sessions touch on dark matter, neutrinos, X-ray sources, astrophysical black holes, neutron stars, white dwarfs, binary systems, radiative transfer, accretion disks, quasars, gamma ray bursts, supernovas, alternative gravitational theories, perturbations of collapsed objects, analog models, black hole thermodynamics, numerical relativity, gravitational lensing, large scale structure, observational cosmology, early universe models and cosmic microwave background anisotropies, inhomogeneous cosmology, inflation, global structure, singularities, chaos, Einstein-Maxwell systems, wormholes, exact solutions of Einstein's equations, gravitational waves, gravitational wave detectors and data analysis, precision gravitational measurements, quantum gravity and loop quantum gravity, quantum cosmology, strings and branes, self-gravitating systems, gamma ray astronomy, cosmic rays and the history of general relativity

    Contemporary Materialism: Its Ontology and Epistemology

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    Materialism has been the subject of extensive and rich controversies since Robert Boyle introduced the term for the first time in the 17th century. But what is materialism and what can it offer today? The term is usually defined as the worldview according to which everything real is material. Nevertheless, there is no philosophical consensus about whether the meaning of matter can be enlarged beyond the physical. As a consequence, materialism is often defined in stark exclusive and reductionist terms: whatever exists is either physical or ontologically reducible to it. This conception, if consistent, mutilates reality, excluding the ontological significance of political, economic, sociocultural, anthropological and psychological realities. Starting from a new history of materialism, the present book focuses on the central ontological and epistemological debates aroused by today’s leading materialist approaches, including some little known to an anglophone readership. The key concepts of matter, system, emergence, space and time, life, mind, and software are checked over and updated. Controversial issues such as the nature of mathematics and the place of reductionism are also discussed from different materialist approaches. As a result, materialism emerges as a powerful, indispensable scientifically-supported worldview with a surprising wealth of nuances and possibilities
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