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[AN] Ivan Trapasso: Explorations in wave packet analysis

In this talk we provide a concise overview of the fundamental principles underlying harmonic analysis in phase space. The roots of this vibrant field of modern Fourier analysis are to be found at the crossroads of signal analysis, mathematical physics, representation theory and analysis of partial differential equations. The key idea is to exploit a dictionary of oscillating wave packets (or equivalently, the combined structure of translations and modulations or dilations) to investigate properties of functions, distributions and operators in terms of suitable companion phase space representations.

Addressing time and frequency/scale on the same level presents both advantages and challenges due to the uncertainty principle. In essence, time and frequency exhibit a somewhat dual nature as variables, hence the efforts to handle them concurrently are ultimately directed to keep track of the multifaceted manifestations of their entanglement. We will delve into these issues, whose origins date back to the foundations of quantum mechanics, and show how they continue to stimulate insightful research in analysis.

Lastly, we will offer a taste of applications of these techniques to some problems motivated by the current challenges of data science, mostly in order to convey the message that the principles of time-frequency analysis are ubiquitous, hence adopting a phase space perspective can provide a versatile framework to explore problems from pure and applied mathematics.

Applicants with a Dutch bachelor degree

Admission requirements All applicants have to fulfil the minimal TU Delft admission requirements . Direct admission (no specific requirements) Individuals holding one of the following Dutch degrees can be admitted to the master programme in Computer Science: Bachelor degree in Computer Science & Engineering (Technische Informatica (TI)) from Delft University of Technology, Eindhoven University of Technology or University of Twente Bachelor degree in Computer Science from a Dutch research university Bachelor degree in Electrical Engineering or Applied Mathematics from Delft University of Technology, Eindhoven University or University of Twente and a completed bridging programming in Computer Science & Engineering from TU Delft Bachelor degree Computer Science & Engineering from a Dutch HBO institution (TI) in combination with a completed bridging programme in Computer Science & Engineering from TU Delft. Individual admission (with a Dutch university bachelor degree) If your Dutch university bachelor degree does not give direct admission, you can apply for individual admission if you meet the academic background admission requirements . Please register for the master programme Computer Science via Studielink and send an email to MSc-EEMCS@tudelft.nl . You will receive instructions on which documents to supply for the assessment by the admission committee. Please note: We do not offer a bridging programme to applicants with a Dutch university bachelor degree from outside of the EEMCS faculty. Admission to the bridging programme in Computer Science and Engineering If you have a Dutch HBO bachelor degree in Computer Science and Engineering (Technische Informatica) or a WO bachelor degree in Data Science and Artificial Intelligence Technology you may be eligible for a bridging programme that after completion gives admission to our master programme in Computer Science. For more information please send an e-mail to MSc-EEMCS@tudelft.nl

Applicants with a Dutch bachelor degree

Admission requirements All applicants have to fulfil the minimal TU Delft admission requirements . Direct admission (no specific requirements) Individuals holding one of the following Dutch degrees can be admitted to the master programme in Computer Science: Bachelor degree in Computer Science & Engineering (Technische Informatica (TI)) from Delft University of Technology, Eindhoven University of Technology or University of Twente Bachelor degree in Computer Science from a Dutch research university Bachelor degree in Electrical Engineering or Applied Mathematics from Delft University of Technology, Eindhoven University or University of Twente and a completed bridging programming in Computer Science & Engineering from TU Delft Bachelor degree Computer Science & Engineering from a Dutch HBO institution (TI) in combination with a completed bridging programme in Computer Science & Engineering from TU Delft. Individual admission (with a Dutch university bachelor degree) If your Dutch university bachelor degree does not give direct admission, you can apply for individual admission if you meet the academic background admission requirements . Please register for the master programme Computer Science via Studielink and send an email to MSc-EEMCS@tudelft.nl . You will receive instructions on which documents to supply for the assessment by the admission committee. Please note: We do not offer a bridging programme to applicants with a Dutch university bachelor degree from outside of the EEMCS faculty. Admission to the bridging programme in Computer Science and Engineering If you have a Dutch HBO bachelor degree in Computer Science and Engineering (Technische Informatica) or a WO bachelor degree in Data Science and Artificial Intelligence Technology you may be eligible for a bridging programme that after completion gives admission to our master programme in Computer Science. For more information please send an e-mail to MSc-EEMCS@tudelft.nl

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NWO grants funding for innovative research on physical experimental environments

How to move from experiment to mainstream? A consortium led by professor Tamara Metze, has been awarded a prestigious grant from the Netherlands Organisation for Scientific Research (NWO). In search for pathways toward more sustainable futures, Metze and her team will explore how various innovations in field labs such as The Green Village, in urban living labs such as Engy Lab South-East in Amsterdam, and in all sorts of citizens’ initiatives, can be mainstreamed and make more impact on sustainability transitions. Pilot paradox The project ‘From EXperiment to sustainable change: TRAnsformative methodologies for Innovation and learning’ (EXTRA) seeks to overcome a persistent “pilot paradox”. In this paradox, much experimentation takes place but long-term systemic impact remains difficult. Researchers together with all sorts of change makers will synthesise existing knowledge on how to mainstream, upscale, spread, broaden and deepen developed innovations. Tamara Metze: ‘I am excited to unravel what are effective ways of cocreation that lead to mainstreaming the positive changes made in experimental environments. We will figure out how learning and innovation can lead to lasting changes in regulations, policies, and financial systems and the biophysical environment.’ Tamara Metze Read the NWO press release Actionable tools The project is crucial for accelerating sustainability transitions. By refining methodologies for mission-driven experimentation and develop hands on tools for all sorts of change-makers, it will be easier to mainstream the sustainable lessons and innovations. ‘These tools will not only aid grassroots innovators but also influence institutional and organisational structures, ensuring that lessons learned from experiments are better anchored in policies, regulations, and organisations’, explains Metze. The project will employ a transdisciplinary action research approach, bringing together knowledge from various disciplines and policy domains. By co-creating solutions with public and private partners, the research will have an immediate impact. In the long term, the project aims to build a more efficient innovation ecosystem, contributing to more impactful and sustainable outcomes for both society and the environment. Projectpartners TU Delft, VU Amsterdam, Wageningen University & Research, Hogeschool van Amsterdam, Erasmus Universiteit Rotterdam, Hogeschool Rotterdam, The Green Village, AMS Institute; PBL Planbureau voor de Leefomgeving, WoonFriesland, Dijkstra Draisma, Provincie Noord-Holland, Ministerie van Binnenlandse Zaken, PRICE / Almere, BouwLab, Alliantie Samen Nieuw-West, Innovation Quarter.

Unusual waves grow way beyond known limits

Waves that come from multiple directions are extremer than extreme. These remarkable deep-sea waves can be four times steeper than what was previously imagined, as is shown in research by TU Delft and other universities that was published in Nature today. A long time ago, stories were told of mysterious rogue waves that materialised out of nowhere and could topple even the largest ships. These waves lost their mythical character when the first rogue wave was recorded at the Draupner platform in the North Sea. In 2018, Ton van den Bremer and his colleagues at the Universities of Edinburgh and Oxford managed to recreate the Draupner wave in the lab for the first time ever, and this opportunity to study freak waves closely produced unexpected insights. Multiple waves push up water New research by the research consortium now shows that these remarkable waves do not break when traditional theories hold they should, the secret behind which lies in how they arise. Ton van den Bremer, expert on fluid mechanics at TU Delft and led the study, explains: “When most people think of waves, they think of the rolling waves you’d find on a beach. The type of wave we studied occurs in open water and arises when waves coming from multiple directions come together. When these waves with a high directional spread converge, the water is pushed upwards, forming a partially standing wave. An example of this is known as a crossing wave. How crossing waves arise Under certain conditions at sea, waves from multiple directions occur. This can happen in a place where two seas meet, or where winds suddenly change direction, as in a hurricane. When waves from two directions meet, a cross wave occurs, provided their directions are far enough apart. The study also shows that the further apart the directions are, the higher the resulting cross-wave. Travelling waves break when they reach a certain limit, this is when they reach their maximum steepness. The study shows that waves with a multidirectional spreading can get as much as 80% steeper than this limit before they start breaking, which means they can get almost twice as high as ‘normal waves’ before they start to break. Travelling wave (l) and a wave with high directional spreading (r) Breaking waves that grow Next, the researchers found another highly unusual phenomenon that defies existing theories, a phenomenon that is unprecedented according to Van den Bremer: “Once a conventional wave breaks, it forms a white cap, and there is no way back. But when a wave with a high directional spreading breaks, it can keep growing.” The study shows that these enormous waves can grow to twice their original steepness while breaking, which is already twice bigger than the conventional limit. Together, the waves can grow four times steeper than previously thought possible. Damage to offshore structures The knowledge that multidirectional waves can become as much as four times larger than was deemed possible can help design safer marine structures. "The three-dimensionality of waves is often overlooked in the design of offshore wind turbines and other structures in general; our findings suggest this leads to designs that are less reliable", says Mark McAllister of the University of Oxford, who led the experiments and is now a senior scientist at Wood Thilsted. Innovative vertical sensors made it possible to take accurate 3D measurements of waves. Innovative 3D measurement method A 3D measurement method developed in the FloWave lab paved the way for these new insights. “Conventional 2D wave measurement methods weren’t up to the task”, Van den Bremer explains, which is why the research group designed a new way to create 3D wave measurements. Ross Calvert of the University of Edinburgh: “This is the first time we've been able to measure wave heights at such high spatial resolution over such a big area, giving us a much more detailed understanding of complex wave breaking behaviour." FloWave Ocean Energy Research Facility in Edinburgh. The circular basin has a diameter of 25 metres and can be used to generate waves from multiple directions. Header image by: Fabien Duboc