Spotlight on Young Researchers: Hussein Rappel


Hussein Rappel uses a mathematical learning approach to try to predict and simulate physical phenomena. The Iranian national came to Luxembourg in 2014 to join the team of Prof Stephane Bordas at the University of Luxembourg, where he is now in the 3rd year of his PhD in Computational Science – and sees great potential in Luxembourg as a research destination.

Hussein Rappel has a thirst for learning new things, and in research has found the ideal job for a curious, knowledge-hungry computer scientist. Since 2014, Hussein has been working with Prof Stephane Bordas, a renowned computational science researcher at the University of Luxembourg. ‘Computational science’ is a broad term nowadays, so what exactly does Hussein do for his PhD work?

Simulating physical phenomena

“We try to simulate physical phenomena (e.g. fracture, deformation and etc.), using mathematics and computer programming.

“In my research I am trying to use a mathematical learning approach called ‘Bayesian inference’ to identify the parameters for the material behaviour laws. The approach is very similar to what we do in our regular life to learn about an event and predict the next step. As an example you can imagine yourself driving your car, for any action that you are going to take for the next step you combine the current state information (the car speed, its position etc.) with the information from your surroundings ( such as the other cars, road situation…) and then you make your decision.

“This is almost what I do in my research by combing the measurements, the information that I already have and my physical model I identify the parameters for governing physical laws.”

In terms of what this looks like on in practice, Hussein explains that apart from reading up on the latest findings in his field and developing the mathematical models and codes needed for the simulation, discussing his findings and progress with his supervisors Dr Lars Beex and Prof. Stephane Bordas is a significant part of his regular activities.

Learning how to do original research in an up-and-coming research location

Being just over halfway through his PhD and thus still at the beginning of his research career, Hussein’s main goal as a researcher at the moment is mainly to learn how to do original research independently and publish the associated results – he adds: “Furthermore I would like to improve my skills by learning to write research proposals which would let me to convert my ideas from a simple idea to a research project.”

Hussein relocated from Iran to Luxembourg for his PhD, which he explains was more due to the chance to work PhD supervisor Stephane Bordas, (who himself came to Luxembourg a few years ago with his then newly-awarded ERC grant), than due to Luxembourg itself. As Hussein points out, however, the University of Luxembourg is slowly but surely building a reputation for itself:

“Considering the condition in Luxembourg and available resources I believe the country is going in the right direction and has great potential to become a very popular destination for researchers from various countries in the world.

“The University of Luxembourg is quite young but it gets recognised every year more than the previous year as it is a research-oriented university. Furthermore the possibility of creating various research centres in the university framework can help it to get even more research-oriented and as result more recognised.

“As an example you can consider creation of the Centre of Excellence in Scientific Computing which can help to do lots of interdisciplinary projects. These research projects can be in fields of finance, engineering, physics and so on.”

“This shows a schematic of Bayesian inference for parameter identification in Biomechanics. The figure in general shows how the Bayesian updating approach works for a parameter identification problem.”

“This figure shows the Bayesian inference prediction for the elasticity constant (Young’s modulus) after having one observation. As it is shown, the inference output is a probability density function which shows degree of our knowledge about the parameter of interest.”

“This shows the Bayesian approach output after four updates, or in other words, after having four measurements. One can see that as the number of our measurements increases the uncertainty decreases.”

Hussein Rappel

About Spotlight on Young Researchers

Spotlight on Young Researchers is an FNR initiative to highlight early career researchers across the world who have a connection to Luxembourg. This article is the 21st in a series of around 25 articles, which will be published on a weekly basis. You can see more articles below as and when they are published.

Spotlight on Young Researchers: Jo Hoeser

Ever since he was a child, Jo Hoeser wanted to understand the function of complex systems. He found himself taking apart and trying to fix broken electronic devices. Then fascination for chemistry came into the mix. Fast forward some years and the Luxembourg national completed his AFR PhD in biochemistry at the Albert-Ludwigs University Freiburg – and wants to return to the Grand Duchy to continue his career in research.

Spotlight on Young Researchers: Thomas Elliot

When Thomas Elliot (Tom) cycled from Indonesia to London, he witnessed many people living in hardship. Motivated to research how consumption affects social and environmental justice in a bid to help reduce the hardship witnessed, the New Zealand national applied for an open PhD position at the Luxembourg Institute of Science and Technology (LIST), where he now works on a project that fuses urban metabolism and ecosystem services.

Spotlight on Young Researchers: Eva Lagunas

Eva Lagunas has always been curious about technology, even building her own makeshift smartphone when she was a child. A couple of degrees later, the Spanish national set her sights on coming to Luxembourg, family in tow, to take up a Postdoc position at the University of Luxembourg’s Interdisciplinary Centre for Security, Reliability and Trust (SnT). Now, she feels lucky to spend her time researching satellite communications in the 5G era.

Spotlight on Young Researchers: Understanding our immune system

Stemming from Italy, Indonesia, Luxembourg, Portugal and Spain, the members of the Experimental & Molecular Immunology Group truly are an international team. In the group of FNR ATTRACT Fellow Prof Dr Dirk Brenner at the Luxembourg Institute of Health (LIH), the team of young researchers investigates different aspects of the immune system with one common goal: Understanding how our immune system is regulated by different mechanisms – and how this knowledge can be used to combat disease.

Spotlight on Young Researchers: Noémie Catherine Engel

Noémie Catherine Engel has just begun her researcher journey – and she has found her niche already: As part of her AFR PhD at the University of Bath, the Luxembourg national investigates the evolution of sex role traits in a small shorebird species in Cape Verde.

Spotlight on Young Researchers: Remko Nijzink

Climate change affects vegetation and water resources. In order to understand these changes, scientists use models – an abstract, mathematical representation of an ecological system. The challenge: Making accurate predictions under change, without ‘tuning’ models with data. We speak to Dutch national Remko Nijzink, Postdoc in the group of FNR ATTRACT Fellow Dr. Stan Schymanski at the Luxembourg Institute of Science and Technology (LIST), about his modelling work and the importance of an open science approach.

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