Recent news

NWO grants for six new PhD positions

05-17-21

Out of the 24 applications awarded by NWO for PhD positions in the Netherlands within the mathematical clusters, 6 have been awarded to mathematicians at VU Amsterdam.

Universal equation for explosive phenomena

05-10-21

Mathematicians find core mechanism to calculate tipping points. Climate change, a pandemic or the coordinated activity of neurons in the brain: In all of these examples, a transition takes place at a certain point from the base state to a new state. Researchers at the Technical University of Munich and VU Amsterdam have discovered a universal mathematical structure at these so-called tipping points. It creates the basis for a better understanding of the behavior of networked systems.

VU Amsterdam students win prize for vaccination planning

02-16-21

VU students win a challenge to design an integrated logistical and creative solution for a long-term planning for a pandemic vaccination program that can vaccinate quickly, carefully, responsibly and accurately potentially 95% of the population in the Netherlands.

KUHN AWARD FOR MATHEMATICS RESEARCHERS

02-10-21

Optimizing barge utilization in hinterland container transportation

Stieltjes prize for Bente Hilde Bakker

01-28-21

VU Mathematics PhD student Bente Hilde Bakker awarded Stieltjes prize 2019/2020

MATHematics RESEARCHERS ANALYZE SUICIDE PREVENTION HELP CALLS DURING PANDEMIC

01-21-21

Stichting 113 Suicide Prevention helps people that are in mental distress and have thoughts about suicide through supporting conversations via telephone and chats. PhD student Salim Salmi at the Mathematics Department in the Analytics and Optimization group, analyzed conversations between Stichting 113 caregivers and clients before and during the COVID-19 pandemic, together with experts from Stichting 113, CWI and Vrije Universiteit Amsterdam (Rob van der Mei and Sandjai Bhulai). The research was partly funded by the COVID-19 programme of ZonMW.

ERC Consolidator Grant for Assia Mahboubi

01-14-21

Assia Mahboubi received an ERC Consolidator Grant for her research project "Fast and Reliable Symbolic Computation"

Predicting occupancy levels with Covid-19 patients in Dutch hospitals

12-21-20

On request of the Landelijk Coördinatiepunt Patiëntenspreiding (LCPS, lcps.nu), Prof. Ger Koole and Dr. René Bekker (VU-Amsterdam), together with Michiel uit het Broek who is a postdoc in Groningen, developed a model to predict occupancy levels with covid-19 patients in Dutch hospitals.

VU Amsterdam students win prize for vaccination planning

VU students win a challenge to design an integrated logistical and creative solution for a long-term planning for a pandemic vaccination program that can vaccinate quickly, carefully, responsibly and accurately potentially 95% of the population in the Netherlands.

02/16/2021 | 1:03 PM

The students Tara Zver, Nina Malbasic, Renze Dijkstra, Berend Markhorst, and Daan Otto won a challenge that was stated by the Top Sectors Logistics, LSH, ICT and Creative Industry in December 2020. Their submission "A fast and responsive supply chain" presents an integrated logistical and creative solution for a long-term planning for a pandemic vaccination program. The project was supervised by Dr. Dennis Moeke (HAN University of Applied Sciences) and Prof. Rob van der Mei (mathematics, VU Amsterdam). 

More information (in Dutch)

KUHN AWARD FOR MATHEMATICS RESEARCHERS

Optimizing barge utilization in hinterland container transportation

02/10/2021 | 1:03 PM

Naval Research Logistics (NRL) has awarded the Harold W. Kuhn Award 2020 to Bernard Zweers, Rob van der Mei, and Sandjai Bhulai for their paper “Optimizing barge utilization in hinterland container transportation”  

The article was selected from 120 papers published in NRL from 2017-2019. The award is presented annually to the best paper published 

in the journal in the previous three years.

Optimization of hinterland container transport

The authors focus on hinterland container transportation using barges since it is getting more and more important. They propose a re

al-life operational planning problem model from an inland terminal operating company. The number of containers shipped per barge is m

aximized, and the number of terminals visited per barge is minimized. This problem is solved with an integer linear program (ILP), yielding substantial cost reductions, about 20%, compared to the method used currently in practice. Furthermore, they developed methods that make calculations regarding practical operational problems regarding container transportation in just a few seconds. The solutions produced by these fast methods are shown to be close to the optimal solution.

NRL praises the publication for its relevance in the nomination letter: “The relevance of the problem is particularly significant in countries like the Netherlands, where barges must be used to transport containers in

Sandjai_Bhulai_photoRob_vdMei_PhotoBernard_Zweers_pic

land. If only trucks were used to transport containers, one would see a continuous line of trucks between the port of Rotterdam and the German border, for example. Barges also produce little polluting emissions and are therefore environmental friendly.”

Co-author Bernard Zweers graduated Cum Laude on 19 January 2021 for his research on the optimization of hinterland container transport, resulting in the dissertation “Optimization of hinterland container transportation and terminal operations” at Vrije Universiteit Amsterdam, under supervision of professors Sandjai Bhulai, Rob van der Mei, and Guido Schaefer.

Stieltjes prize for Bente Hilde Bakker

VU Mathematics PhD student Bente Hilde Bakker awarded Stieltjes prize 2019/2020

01/28/2021 | 1:03 PM

The Dutch Platform for Mathematics (PWN) has awarded the Stieltjes prize for the best PhD thesis in mathematics in the Netherlands in the year 2019/20 to Bente Hilde Bakker. She received her PhD degree at Vrije Universiteit Amsterdam in September 2019, with supervisors Jan Bouwe van den Berg and Rob van der Vorst, for her thesis “Nonlinear Waves in Local and Nonlocal Media — a Topological Approach”.  The jury selected the winner from a total of 76 candidates. 

From the jury report: Bente Hilde’s thesis explores the ways in which algebraic-topological machinery, originating in the Calculus of Variations, can be used to study the existence and multiplicity of traveling wave solutions to a large class of Reaction Diffusion Equations that take nonlocal interactions into account. Inspired by Floer homology and Conley’s earlier theory of isolated invariant sets, she uses topological information to count traveling waves in Morse theoretic spirit. And by adapting Noether’s theorem to a nonlocal setting she identified new conserved quantities. The abstract theory relies on technical conditions (such as ‘transversality’) and to verify these involves hard PDE analysis, in particular Carleman estimates. It was absolutely unclear that such estimates could be derived for equations with nonlocal terms, but she managed, thus showing impressive technical skills. Bente Bakker’s very general and imaginative adaptation of the Floer-Conley methods provides a new framework for thinking about traveling waves that is bound to spawn many new investigations. She deserves the prize for the abstract approach, both elegant and efficient, for the astonishing creativity in breaking down barriers previously thought impenetrable, and, last but not least, for the potential future impact on the description and understanding of coherent structures, with applications spanning nonlinear optics, fluid dynamics, and self-organized structures in biology or sociology. One of the referees wrote: “I believe Bakker’s PhD thesis is at a level that one only sees once a decade”.

MATHematics RESEARCHERS ANALYZE SUICIDE PREVENTION HELP CALLS DURING PANDEMIC

Stichting 113 Suicide Prevention helps people that are in mental distress and have thoughts about suicide through supporting conversations via telephone and chats. PhD student Salim Salmi at the Mathematics Department in the Analytics and Optimization group, analyzed conversations between Stichting 113 caregivers and clients before and during the COVID-19 pandemic, together with experts from Stichting 113, CWI and Vrije Universiteit Amsterdam (Rob van der Mei and Sandjai Bhulai). The research was partly funded by the COVID-19 programme of ZonMW.

01/21/2021 | 1:03 PM

The research shows that people need a conversation during the corona crisis, but find it difficult to talk about feelings in their own environment. Since the start of the corona crisis, men have suffered more from anxiety and young people experience less self-confidence.

Goal of the research

The main goal of the research was to determine whether the subject of help calls has changed under influence of the COVID-19 pandemic. The most common conversation topics during this period were mapped as well. The researchers also wanted to gain insight in differences between conversations of different target groups (young/old, man/woman, living alone). The study analyzed 8,589 chat conversations: 5,179 conversations prior to the corona crisis and 3,410 conversations after the introduction of government measures for corona. For the analysis, specific Machine Learning and Natural Language Processing techniques were used.

Machine Learning method BERT

The machine learning method Bidirectional Encoder Representations from Transformers (BERT) was used to find topics in the chats. This model converts texts into numerical representations that can be used for calculations. This means that each chat message is converted to a numeric representation and clustered. For each cluster the researchers used the corresponding chat messages to arrive at a number of words that describe the group. For this, a selection was made of the 2000 most used words. With help of the so-called term frequency–inverse document frequency (TF-IDF) statistic the most important words were determined. With this selection of words and accompanying chat messages, the researchers found a topic of conversation for each cluster, for example ‘panic and anxiety’, ‘suicide thoughts’, and ‘friendship’.

Conclusions

In fourteen percent of the requests for help, "Corona" was a topic of discussion, after introduction of corona measures. Problems experienced by help seekers that mentioned corona were more loneliness, fear, little distraction, less assistance, threat of unemployment and drug abuse.

Most of the changes in topics of conversation in the 113 Suicide Prevention Helpline, following the implementation of the Corona measures, are as expected. Worrying changes are the increase in panic and anxiety in men, the increase in lack of confidence in oneself or others among younger people, and the increase in suicide plans among people seeking help who live alone.

It is especially striking that gratitude for the conversation itself as well as for listening to the person in distress have increased after the introduction of the Corona measures, especially among men and youth. This means that the 113 Suicide Prevention helpline seems to meet the need for contact with these groups of clients. Fortunately, no increase in the total number of suicides in the Netherlands has been observed over the period from March 2020 up to and including November 2020. In order to ensure that the number of suicides does not rise in 2021, it is crucial to stay alert and discuss feelings together.

More information

ERC Consolidator Grant for Assia Mahboubi

Assia Mahboubi received an ERC Consolidator Grant for her research project "Fast and Reliable Symbolic Computation"

01/14/2021 | 1:03 PM

Assia Mahboubi, a permanent researcher at Inria (France) and endowed professor (by Foundation CAN) at the VU Department of Mathematics, has received an ERC Consolidator Grant for her research project "Fast and Reliable Symbolic Computation". She will investigate how computational mathematics can benefit from recent spectacular advances in software tools for expressing and verifying mathematics in a rigorous logical language. More details can be found in this interview.

 

Predicting occupancy levels with Covid-19 patients in Dutch hospitals

On request of the Landelijk Coördinatiepunt Patiëntenspreiding (LCPS, lcps.nu), Prof. Ger Koole and Dr. René Bekker (VU-Amsterdam), together with Michiel uit het Broek who is a postdoc in Groningen, developed a model to predict occupancy levels with covid-19 patients in Dutch hospitals.

12/21/2020 | 1:03 PM

On request of the Landelijk Coördinatiepunt Patiëntenspreiding (LCPS, lcps.nu), Prof. Ger Koole and Dr. René Bekker (VU-Amsterdam), together with Michiel uit het Broek who is a postdoc in Groningen, developed a  model to predict occupancy levels with covid-19 patients in Dutch hospitals. The model statistically predicts arrivals, which subsequently are translated into occupancy levels of hospitals using queuing theory. This model is used to redistribute patients over hospitals in the Netherlands and the long-term predictions are meant for political decision making.