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: Anjali Sharma

In school, we are taught three states of matter: solid, liquid and gas. The focus of University of Luxembourg PhD candidate Anjali Sharma’s research lies between solid and liquid: liquid crystal. She studies them in unusual shapes that are no larger than the width of a human hair, yet they are considered as large by the scientists of the field. As part of her research, the Indian national got an opportunity for a rare experiment: Taking her research into a zero gravity environment.

Spotlight on Young Researchers: Silvia Girardi

Silvia Girardi is a sociologist with an interest in studying policies that aim to contrast poverty. As part of her joint PhD at Luxembourg Institute of Socio-Economic Research (LISER) and KU Leuven, the Italian national looks at the social policies that support low-income households in Luxembourg, taking the perspectives of the citizens on the receiving end, and the social workers involved in implementation.

Spotlight on Young Researchers: Gilles Tossing

Gilles Tossing’s fascination for the human brain – and why it sometimes fails – led him to the path of research. Now in the second year of his AFR PhD at Université de Montréal in Canada, the Luxembourg national investigates neurodegenerative diseases, with the aim of improving treatments for those affected.

Spotlight on Young Researchers: Sumit Gautam

While we frequently hear about new trends in mobile and wireless technologies, challenges remain, such as the need to charge devices on a stationary device. At the SnT at the University of Luxembourg, Postdoc Sumit Gautam works on solving the future information and energy requirements of wireless devices, via radio frequency (RF)-based techniques.

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: Anna Monzel

Anna Monzel cites her thirst for new knowledge and discoveries as a key contributor in her choosing to follow the path of science. Drawn to Luxembourg because of its interdisciplinary approach, the German national developed a 3D model of the human midbrain for her PhD at the LCSB at the University of Luxembourg – which earned her a Lush Young Researcher Prize.

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