VOLUME II
Stories of EEMCSEEMCSNODESVOLUME II

A treasure trove of stories
Preface
Dear Lucas,

Hello John,Over the past years, I’ve often been asked the question:

What a warm bath, and what a great start! In a

John, this faculty of yours... what actually goes on

world in which Covid-19 is striking mercilessly andthere? I might be asked it during a New Year’s reception

indiscriminately, and many of us are forced to work

or at a major international conference, or even at afrom home, this book is a very welcome gift. Whatfamily birthday party. So I’m really thrilled to be able to

I would most like to do is to personally shakeproduce a book from my briefcase that describes all

everyone’s hand and listen to all the research project

the fine research we do – beautifully written in simple

stories while enjoying a cup of coffee. But – sadly –language.

that is not possible. That is why this book makes meeven happier. It is the best and the quickest way to

Just like the first edition, this book is a treasure trove

get to know the faculty. John, thank you so much forof stories – stories that are set within our faculty walls

everything. In the coming years I will do my very, very

but that reverberate far beyond. These are stories thatbest to continue all your good work.

generate a sense of optimism. For example, you canread how you can use mathematics to determine theKindest regards,

germination capacity of potatoes and so contribute toaddressing the ever growing global demand for foodLucas van Vliet(Health), how computer graphics are set to broaden our

Dean of the Faculty of Electrical Engineering,experience of art (Digital society) and we will soon be

Mathematics and Computer Science (from 2021)

able to tackle worldwide energy challenges in the new
ESP Lab (Energy transition). What one word links allthese EEMCS stories? Impact! Each and every one ofthese research projects puts something in motion. I amvery proud of this. And I am very proud to present you
with this great book.
All I can say is: read and be amazed. And at the sametime, be aware that these are just a few of our stories.
You will undoubtedly read more in a next edition in thisseries. Because packing all the EEMCS treasures into
one volume would result in a book no letterbox in the
Netherlands could accommodate. Lucas, I wish you a
lot of success in the coming years and I'm sure you'regoing to enjoy all the wonderful research that is taking
place within walking distance of your new office.
Have a good read!
John Schmitz
Dean of the Faculty of Electrical Engineering,
Mathematics and Computer Science (2016-2020)

22020 | EEMCS NODES VOLUME II

3

Table of contents

PAGE

No

TITLE 		PAGE

01	A fresh perspective on potato growth

6

16

Using mathematics to explain why the River Ems is silting up

102

02	Smart data collected from grandmother’s living room

1217	From micro to macro with duality

108

03

A bit of math to constrain epidemics

20

18	Affordable MRI

114

04

The impact of algorithms

26

19	Organizing high-dimensional data with triangles and fields

120

05

Algorithms unravel cellular dynamics, and what it means for targeted therapy

34

20	So much more than 3D visualisation

128

42

21

134

No

TITLE 		

06	Increased road safety with highresolution automotive radar07	You only know the best method of defence when you understand more

How not to waste energy on 5G

22	Is sharing personal data a matter of all or nothing?

142

50

23	Solar cells available at bargain prices, but still the revolution stagnates

146

08	Protecting the electricity grid of the future

56

24

152

09	Computer as a sheepdog

60

25	Improving the effectiveness of speech recognition

156

10	Intermittent computing to replace trillions of batteries

66

26	Diagnosing tuberculosis with algorithms

164

11	Developing a digital twin for the electricity grid72

27	Tackling tumours using mathematics

170

12	How smart sensors can prevent epilepsy

7628	Ultrasound from a plaster

178

13	Modelling a flexible electricity system

84

29	A glimpse into the universe with superconducting electronics

184

14	New Electrical Sustainable Powerlab smooths the way for energy transition

90

30	We\Visit: combatting loneliness with video-calling

192

15	Understanding noise – from quantum fluctuations to climate models

96

about your opponent

4

A post-coronavirus society

2020 | EEMCS NODES VOLUME II

5

A fresh perspective
on potato growth01

Text: Merel Engelsman | Photography: Mark Prins

Requiring less water and less time to grow than rice, corn
or wheat, potatoes may well be the answer to the growing
worldwide demand for food. But what are the key factors that
determine a successful potato harvest? Asked to provide a fresh
perspective, Neil Budko develops numerical methods for the
analysis of carefully controlled potato growth experiments.

62020 | EEMCS NODES VOLUME II

7

‘It’s a typical inverse problem - theobserved vitality is the effect and now
we want to determine its causes.’

The Flight to Vitality project
The soil in the north of the Netherlands
is especially well-suited for growing seedpotatoes. Farmers buy these seeds from theproducers in order to grow potatoes for actual
consumption. Both producers and farmers
would like to know the vitality of seed potatoes

A bit of potato funprior to planting. ‘Vitality is defined as the‘About ten years ago, I switched from electrical

proportion of seed potatoes that emerges

engineering to my current position,’ says Neilfrom the soil and their uniformity of growth

Budko, associate professor in the Numericalafter emergence,’ Budko explains. ‘The current

Analysis Group at TU Delft. ‘It was a shift

standard for determining their vitality is to picktowards research with a more direct practicala bunch of potatoes, put them in a bucket for

application. I like that.’ His first exposure toa week, and see how many become rotten.

agriculture was a quirky little assignment

You would think this methodology is easy tofrom a Dutch company specialized in seedbeat, but it is actually very hard to come up

potatoes. ‘We met at a yearly industrial-

Neil Budko, associate professor in the
Numerical Analysis Group at TU Delft.

academic workshop where companies posewith a systematic procedure.’ This is what the
Flight to Vitality project is about, which also

problems to a group of mathematicians, to be

involves the two seed potato companies andsolved within a week. They wanted to know

Utrecht University. ‘As the major contributor,

how to best cut potatoes into fries,’ he says.

we are responsible for all the math and data

‘It was a fun project, although scientificallyof about twelve centimetres. It develops

not very challenging. After a few more of

sprouts, which grow into stems that willsuch projects, however, I realized there is

eventually emerge from the ground. These

Climate control and drones

something in seed potatoes that fits well withstems develop leaves. The more (large) leaves‘At the end of this project, we want to be

my background in inverse problems. That isthey have, the more excess nutrients to beable to just look at a batch of seed potatoes,

a class of problems in which the outcome isstored and the more potatoes to be harvested.

measure the few aspects that we figured out

known and where you want to determine the‘Many factors contribute to potato growth,’

to be important, and exactly tell you the batch’s

causal factors that produced this outcome.’

Budko says. ‘The potato variety and its genetic

vitality,’ Budko says. To determine these im­constitution, for example, but also the weather,portant aspects, the researchers designed asoil, growth and storage history of the seedvery broad search, focussing on the perfor­

Potatoes are so-called stem tubers. A tuber

tubers.’ Agronomists have spent decades

mance of six potato varieties in all kinds

is a storage organ for nutrients, grown bybuilding a model for growing an ideal potato,

of conditions. Tubers were simultaneously

certain plant species to survive the winter or

resulting in a very complicated equation.

planted in various countries and soils as well

dry spells. Potato plants grow up to twenty‘This model provides a lot of understanding,’

as in two custom-build climate-control roomsof such underground tubers, to be used for

Budko says, ‘but it doesn’t really work as there– a cold and a warm room, each having a dry

consumption or for growing new plants.

are no ideal potatoes. We were contacted by

and a wet section. For each batch of tubers, a

In the latter case, such a tuber is called

two seed potato companies to provide a fresh

lot of data are collected and stored: genetics,

a seed potato and it is planted at a depth

perspective on potato growth.’

microbiomics, storage conditions, organic

Ideal potatoes don’t grow8

processing during the project.’2020 | EEMCS NODES VOLUME II‘Ideal models don’t work.
They came to us for a fresh
perspective on potato vitality.’9

to transform away any of the growth.’ The

Watching potatoes grow in real timegigantic transformation process, involving

The Flight to Vitality project was already underhundreds of pictures each day and thousands

way when Budko became aware of anotherof plants per picture, has to be automated.

longstanding problem in the root vegetables‘Our computers run out of memory. We havebusiness. As all root vegetables grow under-some tricks up our sleeves, but it is not

ground, they need to be dug out for inspection

solved yet.’– a wasteful and time-consuming procedure.

Yielding control, controlling yieldand inorganic constitution. Once planted

more, setting up and conducting experiments

detailed weather data are collected as well.

and collecting data is very expensive and we

Camera-equipped drones are used to monitor

may never have a training set large enough forplant growth – when do they first appear

automated machine learning.’

above ground and how do they continue todevelop. Acquisition of images at wavelengths

Leaf it to the computer

outside the spectrum of visible light allows

Perhaps the most important aspect of thethe researchers to also track changes inongoing research is to measure the vitality ofthe biochemical composition of the plants.

each batch of seed potatoes, in which Budko‘It’s a typical inverse problem,’ Budko says.

is assisted by his PhD Student Elisa Atza

‘We observe the measured vitality, and now

and his master’s student Martijn Bos. Taking

we want to determine what caused thesedrone images is standard industry practice.

effects. We get thousands of signatures,

But rather than a one-time snapshot, theeach consisting of thousands of data points.

researchers want detailed growth information

Gigantic data matrices.’over a period of four to eight weeks. As each

Back to natural intelligenceelectrical engineer – detecting landmines with

‘Obviously, it will be the seed potato’s history

ground radar. I also remembered the limita-

and its chemical constitution that influence

tions of that technique, so we had to comevitality,’ Budko says. ‘What we don’t know yet,up with some other solution.’ Air temperature

however, is the relative importance of eachvaries, with warmer temperatures during theof these factors. The exact proportions of

day and colder temperatures at night. Budko

specific organic and inorganic substances,and his bachelor student Marissa Bezemer

for example. But potato vitality is starting

modelled how this affects the temperature in

to expose some of its secrets to us.’ Vitality

the soil and saw a temperature wave moving

and yield are related. If a plant has emerged

down. They then added the potatoes to thisand temperature and humidity are okay, it willmodel. ‘In soup, potatoes are always theinevitably produce potatoes. ‘That is why we

hot bastards,’ Budko says. ‘They have a very

focus on the first few weeks of plant growth,’

high heat capacity, which leads to local

says Budko. ‘Maximizing production is not

distortions in the temperature wave. We ran

the goal of our project. But if we know what

the simulation for potatoes of various sizes

determines yield, and it is easy to control, why

and got a very cool movie.’ Budko now wants

not?’to put an array of temperature sensors into theground, leaving it there for the whole growthseason. ‘The company involved is very excited,
as nobody can yet measure potato growthnon-destructively.’

photo only covers a small section of thepotato fields, they first need to be stitched‘We can’t use an artificial neural network to

together. They then need to align theseanalyse these data, as we do not have a clas-

aggregate pictures in space and in time, andsification problem but a so-called regression

also extract the growth information. ‘We areproblem,’ Budko explains. ‘Artificial neural net-developing an approach to automaticallyworks are extremely good at classifying things

determine the change between pictures,’– pictures of cats and dogs, or CT-scans with

Budko says. ‘Not just the difference in theor without cancer – and bad at telling you

pixels, but the actual change in the size of

how they do that. We want to understand thethe plants, in each of the leaves. How much

relationships in the data, to determine the root

have they grown in length, how much in width?

causes of potato vitality. We will then perform

Existing algorithms for such deformableadditional experiments to validate the cause-

image registration are not subtle enough. We

effect relationships we have found. Further-

had to develop our own algorithms, so as not

10‘It reminded me of a project I worked on as an‘The current standard for
determining potato vitality is
to put them in a bucket for aweek and see how many becomerotten.’2020 | EEMCS NODES VOLUME II

11

02

Smart data collected from
grandmother’s living room

At first glance, the room where Pablo Cesar works looks likea totally normal office complex, with carpeting, system ceilings
and a pinboard with posters about academic events. Behind

Text: Robert Visscher | Photography: Mark Prins

the doors, you expect to see desks with computers on whichmathematicians are doing calculations. But when Cesar opens
the door, you walk into a cosy traditional Dutch living room, one

Chatting with family on the other side of the world via a holo-

your grandmother would feel at home in. There is a photo ofgram or selecting your own camera angles for your favourite

the king next to a cuckoo clock, and a Persian rug on the floor.

club’s football match. TU Delft computer scientist Pablo Cesar

But this is not where the scientists drink coffee or relax

is researching the best ways of transmitting and receiving data

watching television. ‘This is one of our research labs,’ says

to make these kinds of applications possible. He was recently

Cesar. He points towards an antique lamp. ‘It is fitted withawarded the Netherlands Prize for ICT Research 2020.

‘In order to understandhuman behaviour in thewild, such as dancing ina club, we used machineswith artificial intelligencequickly processing datafrom sensors fromaround 450 people
simultaneously.’a microphone and there are cameras on the walls, so we cananalyse user behaviour. Next door is a computer room where
we test and compare different TV and data configurations.’

122020 | EEMCS NODES VOLUME II

13

About Pablo
Pablo Cesar (1976)has been appointed professorof Human-Centered Multimedia Systems in the
Department of Intelligent Systems (INSY) at TU
Delft (Faculty of Electrical Engineering, Mathematics
and Computer Science). Cesar also leads theDistributed and Interactive Systems (DIS) group at
CWI and is the recipient of the Netherlands Prize
for ICT Research 2020. His research focuses on‘We prefer to conduct our
research in the wild.’

modelling and controlling complex collections ofmedia objects (including real-time media and sensor
data) that are distributed in time and space. In his
research, Cesar in particular focuses on fundamental
problems related to the interaction between people
and technology, and how this interaction can bemodelled. The research of Cesar is not restricted to

Prestigious prize

the lab, but his experiments as well performed in a

The lab disguised as grandmother’s living

realistic context.

room provides an indication of how Cesar andhis colleagues approach their work. They liketo conduct research in as realistic a setting
as possible. They use this method to look at
a wide range of subjects. For example, Cesar
is investigating how we watch TV, he aims to
improve teleconferencing and wants to enable
hospitals and ill people to communicate witheach other.
The computer scientist is an associate
professor in TU Delft’s Multimedia Computing

SCAN!

group and the national research institutefor mathematics and computer scienceCentrum Wiskunde & Informatica (CWI) in
Amsterdam. For his contribution to science,
he was recently awarded the Netherlands
Prize for ICT Research 2020. In its report, thejudging panel highlighted the fact that Cesar’s
work focuses on fundamental problems inhuman/technology interaction and how thesecan be modelled. They also praised Cesar
for conducting his experiments in a realistic
context, rather than a lab setting. ‘We prefer to

Our research group focuses on facilitating and improving
the way people access media and communicate withothers and with the environment. We address key
problems for society and science, resulting from thedense connectivity of content, people, and devices. We
use recognized scientific methods, following a full-stack,experimental, and human-centered approach.

142020 | EEMCS NODES VOLUME II

conduct our research in the wild,’ says Cesar.
‘We’re developing technology for people.
That means that we have to get them to test
what we come up with in order to improve ourideas.’

15

‘It's normally the director who determines
what you see at home. I am interested
in exploring mechanisms for content
customisation and viewer personalisation.’

A good example of his approach is the British

That involves transmitting an awful lot of

FA Cup final. Cesar was asked by the BBC andinformation simultaneously, because you also

British Telecom to design a second screen

want to avoid any delay in the match you’refor people watching the final. He came up

watching. Cesar is developing ways of trans-with a menu that allows you to control all

mitting and controlling the data as smartly as

kinds of things, including the camera angle,

possible. To achieve this, he uses algorithms

extra action replays or the colours around thethat select the relevant information in a smart

screen. ‘It’s normally the programme director

way. This data only is all put in small packets

that determines what you see at home. Ourin a process known as compression – almost

technology gives the viewer more freedom.

like creating a zip file on your computer. The

The director is still in control, as is appropriate

files are pressed together, reducing the spacein view of his or her experience. But he or she

they take up and enabling them to be trans-

gives the viewer multiple options to choose

mitted faster and more easily. The files arefrom.’

then unpacked at the end user where they areconverted to make images or sound. Algo-

This made it possible to show different things

rithms also play an important role here. Cesar

on several screens in a pub full of Chelsea

is investigating how all of this can be done

supporters. One TV showed images of theas effectively and quickly as possible. In thematch whereas another just had a close-up ofprocess, he always has the viewer’s quality of

the coach. The sound came directly from theexperience in mind. What compression results

Chelsea supporters’ stand, so their chanting

in the best image quality, how much image

could be heard in the pub. The result wasdelay is permitted without undermining themuch more tailored to the specific target

connection and what bandwidth is required?

group in the pub.

Communicating with family

This approach may give viewers more options,

Cesar is not only working on watching TV

but what difference does the science makeand second screens. He’s also researching

here? ‘Our primary interest was in the how tocommunication between people. He walks intotransmit all that information at a superfast

a room full of boxes. They have been painted

speed and orchestrate the complex data onpink on one side. There are cameras aroundthe screens. Pictures of the match alreadythem and a researcher is walking round withneed to be transmitted to the TV in the pub or

his arms spread out. Cesar points to a com-

at home at amazing speed. In our case, we

puter screen showing an image of the walking

had to send and control a lot more data, suchman.

as several camera angles and different sound.’

16

Using the technology that Cesar is now working on, you
can create in real-time a highly realistic 3D representationof someone that makes it look as if he or she is standing infront of you.

Imagine you want to discuss something

The image quality required also plays a role.

important with a family member on the other

Displaying someone’s face in high definitionside of the world. It’s now already possible toand the rest of the body less clearly cantelephone them or use Skype. But using thealready make a big difference. Cesar and his

technology that Cesar is now working on, youcolleagues are testing people’s responses tocan create a hologram of someone that ma-

this. ‘We are trying to figure out which bits of

kes it look as if he or she is standing in front

data are important to send and receive andof you. He is working on this in this room.

which are not.’‘We create a 3D image of someone. The

This up-and-coming technology is not only

result is a large file that we compress anduseful for phoning your family. It can also

decompress when it reaches the receiver.

be used for teleconferences with businesses,

It’s similar to what we did for the FA Cup. But

or in hospitals. ‘For example, if you needwhat’s the most practical approach? If I wanta knee operation, you can have the necessary

to talk to a family member in Spain, whereappointments for tests in the hospital. Any

I come from, they don’t need to see my back.

other appointments can be done by a tele-

That means that we don’t have to send allconnection, with the doctor receiving a veryof the images. These are very large files, sohigh definition image of the knee. This will

we’re investigating how we can make themalso help the advance of healthcare in thesmaller by removing useless noise.’future.’2020 | EEMCS NODES VOLUME II

17

Disco of the future

When the feet really hit the floor, it was very

This is not pure chance. Cesar and his

But it’s not only healthcare – even a disco canrelaxed in the second room. If everyone oncolleagues are interested in the entire chain

benefit from Cesar’s research. Several years

the dance floor was acting like a wallflower,

across which information is transmitted andago, Cesar was asked to work on a project at

the second room was incredibly hectic. ‘Byreceived. It’s an approach he believes in.

the Amsterdam Dance Event (ADE). One of thedoing this, we learnt how to process a lot of‘We’re living in an age when many scientists

sponsors asked him to make the club of theinformation rapidly and also how to display

are focusing on a very small thing or subject.

future possible. Cesar therefore joined forces

it immediately to visitors. The result was not

We look at things from a broader perspectivewith clothing designer Borre Akkersdijk toonly a great disco, but something that we, as

and always focus specifically on how

come up with armbands packed with sensors

scientists, could also learn from.’ In scientificinformation reaches people. This has beenthat checked people’s temperature, location

research into what is known as affective com-relatively ignored in the scientific world, but

and movements. This information was thenputing, there is a lot of focus on such issues

our work at TU Delft and CWI is fortunatelytransmitted wirelessly to minicomputers on

as the recognition of emotions by software

now changing that. Winning the ICT prize

the wall. Some 450 people attended. ‘That’sand investigating audience engagement.

in 2020 will certainly help. I hope that the

an amazing number for a scientific study,’

attention it attracts will focus especially on thesays Cesar. ‘We used machines with artificial

In these kinds of projects, the researchersdevelopment of computer science aimed at

intelligence that had to understand where

make a lot of things themselves. This not only

end users and that we will be able to continue

people were and whether they were dancing.

includes the software, such as algorithms toto investigate that even more effectively.’

We then wanted to share that information withdo the calculations, but also the sensors built

the people at the event. For that, we createdinto the armband. Cesar reveals a room full ofa second room that was the opposite of theequipment where there is also a workbench on

dance floor.’

which all of the hardware is made or adapted.

182020 | EEMCS NODES VOLUME II

Cesar joined forces with clothing
designer Borre Akkersdijk to come up
with armbands packed with sensors
that monitored people's temperature,
location and movements, and helped
to understand human behaviour.

19‘For ten years I have used the course of small outbreaks and large epidemics

03

A bit of math to constrain
epidemics

to introduce the concept of mathematical modelling to new university students,’
says Kees Vuik, professor in the Numerical Analysis group at TU Delft. ‘Although
we do explore some mathematical depths, these models are essentiallyrelatively straightforward. It would be great if everybody gained some insight
into these models. We would then better understand why certain measures are,or are not, taken in an effort to control the course of an epidemic.’

Text: Merel Engelsman | Photography: Mark Prins

The dynamics of a simple epidemic

Most people like to keep both mathematics and epidemics
at a distance. But a little bit of the former can do wonders in

For well-known diseases such as the flu, measles, mumps and rubella, thecourse of an epidemic can be accurately predicted using the SIR-model (seefigure). It requires the population to be divided into three groups, so-called

limiting the latter. Supervised by Professor Kees Vuik, two highcompartments: Healthy people, Sick people and Immune people. Those in theschool students modelled a recent outbreak of cholera in Ghana.

group of Healthy people have a certain chance to fall ill, and thereby move to

He also has a bachelor student investigating the new corona
virus.

‘With a bit moreinsight intodisease modelling
we would all
better understandwhy certain
measures aretaken to constrain
an epidemic.’

the group of Sick people. The chance of falling ill increases as the number ofpeople that are already sick and therefore contagious increases. Those in thegroup of Sick people have a certain chance to recover and to thereby move tothe group of Immune people. This very straightforward model correctly predicts
there to be a peak in the number of sick individuals. The magnitude and timing

20

2020 | EEMCS NODES VOLUME II

21λhealthy peopleδ
ill people

immune people

100

The SIR-model has three

percentage of the population

90

compartments: Susceptible

immune80(Healthy), Infectious (Sick)and Recovered (Immune). As70

the number of healthy people

healthy60

continually declines (black lines),50

the number of sick people will first40

rise and then fall (blue lines). The

30

epidemic comes to an automaticill

halt. In the end, everybody has

20

fallen ill and become immune

100‘We wanted to do a project involving mathematics
and we wanted it to have social relevance.’

The SIR-model(white lines).

0

5

10

15

20

25

30 35
weeks

40

45

50

55

60

No longer containedof a single coefficient,’ Vuik explains. ‘But as‘We had to learn some additional mathsoon as they saw the predicted course of theskills,’ Mark says, ‘but we could still explain

epidemic to much better match the measured

our research and the model we used to ourrate of infections and deaths, they could

classmates and family. Not so much how to

no longer be contained. They doubted theof this peak depends on two coefficients. The

contaminated drinking water. That was new tosolve the model using numerical analysis,correctness of all coefficients and they even

first coefficient is a number, the value of whichme. I then asked two high school students tobut certainly the various dependencies in thechanged a dependency in the model.’signifies the speed of sick people infecting

try and apply this model to a recent outbreakmodel and how they influence each other

healthy people. The value of the secondof cholera in Ghana.’ In 2014, more thanas well as the course of the outbreak.’ The

A sewage system but no quarantine

coefficient signifies the speed of recovery ofseventeen thousand people were infected by

students first gained experience by applying‘With our model matching the outbreak insick people. The model can be extended withcholera, with about three hundred of thosethe simple SIR-model to an outbreak of

Ghana we could investigate the measuresaspects such as vaccinations or a latent period

not surviving. The two students, Annelotte

influenza. They subsequently focussed theiravailable to the authorities to constrain an

during which a person is infected but not yet

Baarslag and Mark Tabaksblat of Gymnasium

attention on the more difficult model foroutbreak of cholera,’ Annelotte says. ‘We forcontagious. It is harder to mathematically

Novum in Voorburg, had just been accepted tocholera, including the additional infection

example lowered the value of the coefficientsolve such an extended model.

the Pre-University College of Leiden University

pathway through contaminated drinking

representing the speed with which the cholera

and were eager to get their teeth into it. ‘We

water. The model was also extended bybacteria transfers from humans to local

had many assignments to choose from forincluding both birth and natural death. Next towaters. The authorities can achieve such

‘Early last year, at a conference, I saw a poster

our final research project. We wanted to doassuring that a model correctly represents alla reduction by building a sewage systemdescribing a disease model for cholera,’ Vuik

a project involving mathematics and werelevant dependencies, another big challenge

or by improving an existing one. Our modelsays. ‘The model showed two pathways for thewanted it to have social relevance. Modellingis to determine the correct values of all its

predicted this measure to reduce the totalcholera bacterium to be transmitted – froma disease outbreak was very appealing to us.’coefficients. ‘At first, Mark and Annelotte were

number of people being infected as well asa bit hesitant to as much as change the value

the number of deaths caused by the outbreak.’

Cholera in Ghana

one human directly to another, and through222020 | EEMCS NODES VOLUME II

23

SCAN!

‘And just to think that, at this moment,
mathematicians are actually saving lives.’

known, but the epidemic has only just started,’
Vuik continues. ‘Each day brings new data,
leading to changed insights and updated
values of coefficients: contagiousness, theduration of the latent period, and so on – perage category.’ The models used by the RIVM
are fundamentally similar to the students’cholera model, but they are extremely hard
to solve mathematically as they need to takeso many details into account. The simple

Who is that chalk-spattered individual patiently explaining
differential equations? Who is that man or woman
struggling with the smartboard? And while we’re at it...
where did the unbridled passion for blockchain originate?
These are just three of the questions you will get answers
to from listening to De ProfCast, a EEMCS podcast createdby PhD candidate Marieke Kootte and Master’s student Tijs
Ziere. The first episode will feature Kees Vuik (Numerical
Analysis). Listen to the podcast (which is in Dutch by theway) here.

models assume every person to have a similar
likelihood to be infected, and to be equallycontagious once infected. The model ofthe RIVM applies different coefficients per
age group and gender. They also take into
account highly detailed information about

A futuristic scenario with extended insight‘It is the year 2041. Following a first limited
outbreak under high school students in Voorburg,
mathematical understanding of disease models
has spread all over the Netherlands. The entire
city of Rotterdam is put under quarantine as,after nearly 200 years, it is unexpectedly hit byan outbreak of cholera in its port area. Nobody
was surprised by this drastic measure and no
parliamentary questions were tabled.’

contaminated drinking water. Quarantine or

the interactions between people – who

not, the same number of people will succumbmeets whom, how often and where? It allows

to cholera.’ Professor Vuik adds some nuance

the RIVM to determine the effectivenessto this conclusion. ‘A quarantine does workof countless and quite detailed measures,

if you do not only quarantine people, but also

such as the closing of schools. ‘I currently

the contaminated water sources. This can bealso supervise a bachelor student. He isachieved by restricting access to an entire

investigating whether or not some of thesevillage or region. More comprehensive diseasemeasures also follow from a simpler model

models therefore subdivide an area or country(see frame).

into various regions, while also modelling
travel between these regions.’

It’s in the details

The power of mathematics
Both high school students were alreadyfamiliar with the power of mathematics priorThis was an expected outcome as, mid-

‘The model we used to describe the cholera

to their modelling assignment. It is something

19th century, the Netherlands halted cholera

outbreak is quite advanced and at a scientificthey wish to continue to apply. Annelotte hasoutbreaks by adding a sewage system andlevel,’ Vuik says, ‘but the real know-how isbeen admitted to the navy and will be trained

a pipeline network for drinking water to many

concentrated at the National Institute forto become a maritime officer – a bachelorof its cities. ‘Perhaps the most interesting

Public Health and the Environment (RIVM).’

involving a lot of mathematics and physics.

outcome was that imposing quarantine

The institute houses twenty mathematiciansMark will most likely enrol at Leiden University

measures has absolutely no effect in the

dedicated to disease modelling. At thisto study mathematics and physics. ‘The

case of cholera,’ Mark says. ‘Although it

moment, with the corona outbreak, they

current corona epidemic is so overwhelming,’

reduces the rate of infection between humans,

work around the clock. ‘It is a new diseasehe says. ‘And just to think that, at this moment,

everybody still ends up being infected throughfor which the model dependencies are well-mathema­ticians are actually saving lives.’

242020 | EEMCS NODES VOLUME II

A simple disease model for corona
A bachelor student supervised by Professor Vuik iscurrently investigating if a simpler disease model
can (still) be adequate for understanding why certain
measures are proposed to constrain the current
corona epidemic, such as closing our airspace toflights from certain high-risk countries. The student
will specifically try to explain how this virus was able
to spread around the world so quickly. To answer
this question, he will model the influence of longdistance travel in combination with the probabilityof being contagious while not yet experiencing any
symptoms. ‘I think it may be interesting to add afourth category to the SIR-model, a contagious-butnot-yet-ill compartment,’ says Professor Vuik. ‘The
most important aspect of this research is educating
students. It is not our aim, or our expectation, todiscover something that is of interest to the RIVM,
but it is certainly a possibility.’

25

The impact of algorithms
Text: Merel Engelsman | Photography: Mark Prins, Inge Hoogland04

In our age of technology algorithms have become more complex
and more influential than ever before. And yet, because of theiromnipresence, we are much less aware of them. We only notice their
existence when they stop doing what they were intended for. What
exactly is an algorithm, and what is their impact?
What is an algorithm?
Many people associate algorithms with a computer solving a complex mathematicalproblem. But in its essence, an algorithm is little more than a finite set of instructions forachieving a certain goal. A recipe for preparing a tasty meal also fits this description, but theterm algorithm will indeed more often be used in combination with numbers and computers.
In general, these algorithms process information. Mathematics are important, for example
for translating a real-world problem into a model, which then determines theso-called solution space. The algorithm is a smart way to search for the best

‘Thanks to analgorithm, the user
does not need tounderstand the
problem in orderto solve it.’possible solution within this space. A good algorithm is characterised by it
being both correct and efficient. Efficiency means that the solution will bereached with as few steps – as little computing power – as possible. Thanks toan algorithm, the user does not need to understand the problem in order to solve
it. The inventor of the algorithm, on the other hand, needs to have a thoroughunderstanding on the subject.

Euclid’s algorithm
One of the oldest known (mathematical) algorithms,
defined in 300 BC by Euclid, finds the greatest
common divisor of two numbers. The algorithm
shows great understanding by its inventor, is easy forthe user to apply, and works as follows: Subtract thesmallest number from the biggest number. Repeat
for the new number and the smallest of the two
previous numbers until you reach 0 (zero).
For the numbers 49 and 21, the steps are:49 – 21 = 28, 28 – 21 = 7, 21 – 7 = 14,
14 – 7 = 7, 7 – 7 = 0.
The greatest common divisor of 49 and 21
is the number 7.

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27

SCAN!
As a consumer you often don’t realise
when an algorithm impacts your life.
When the train schedule is adapted
because of a disruption, for example.

In most recent projects Peter Bosman
focuses on topics in radiation
oncology, including automatedtreatment planning, deformableimage registration and 3D dosereconstruction, in close collaboration
with researchers and medical experts
from (academic) hospitals.

Finite applicability
As a consumer you often don’t realise when an algorithm impacts your life. When your phone
automatically adjusts its brightness setting, for example, but also when the train schedule isadapted because of a disruption. In the latter case, an algorithm could perhaps instruct trains not
to stop at your tiny train station for a few hours. It is therefore important to realise the circumstances under which an algorithm stops performing as intended. For certain algorithms, such as
the one by Euclid (see page 27), it can be proven mathematically that they will always function
correctly. For other algorithms, such as the one adjusting the train schedule, this may only be
the case as long as the underlying model accurately represents reality. Removal of a train track
may necessitate the use of a different algorithm, or at least a new optimisation using the existingalgorithm. Deep Learning neural networks, andThe role of computersvirtually all kinds of artificial intelligence, canfind very good solutions, but it is not possible

A computer program is the implementation of an algorithm. Multiple computer programs canto mathematically prove these to be optimal.

lead to the same solution, but they may differ in, for example, the number of calculations needed,

Their training datasets may furthermore beor the amount of storage space. In the early days of the computer age, computational power wasbiased (all training pictures containing catsvery much limited, and the science of algorithms focussed on the discovery and implementation

also contain furniture), resulting in unexpectedof algorithms for problems that were relatively easy to solve, such as finding the shortest route.

network behaviour.

Because of the enormous increase in computing power and in the fundamental knowledge ofalgorithms, this focus has shifted towards problems that were previously unsolvable because

New insightsof their sheer magnitude. Where the need for fast execution of algorithms used to be a driving

The use of existing (combinations of)force behind the development of computers, nowadays powerful computers and the availability

algorithms to solve real-world problemsof huge digital datasets have led to the development of new algorithms. Machine Learning isalmost always results in suboptimal solutions

currently drawing most of the attention.

that are either too slow or not accurate

Machine Learning

enough. To fix this, the underlying model
may have to be over-simplified. A researcher

In Machine Learning, a kind of artificial intelligence, it is no longer human understanding thatwill then implement

powers the algorithm. Rather, it is the algorithm itself that uses a large dataset to determine asmart improvements

relationship between input and output. In this process, the role of humans is limited to gathering

to build a suitablea correct and sizable dataset for training the algorithm, designing the underlying artificial neuralalgorithmic solution.

network (in case of the highly popular Deep Learning approach), and the decision of whether

These algorithmicor not to release the trained network into real-world operation. Machine Learning has led toinsights often have a

breakthrough successes in bioinformatics and in the fields of speech and image recognition.

significance beyond theMachine Learning networks outperform humans in certain tasks, but they do not think likescope of the problem

humans. In fact, their inner workings are so complex that it is often impossible for a human tojust solved.

‘An optimal solutionthat isn’t fair, is not
optimal to me.’Mathijs de Weerdt

determine how and why a Machine Learning network makes certain decisions. Their elusivenessmay give them a somewhat spooky quality, as their influence on our daily life is continually
increasing.

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Mathijs de Weerdt

Theresia van Essen

A fair energy transitioncase of capacity issues. This may be the best

Optimal spread of ambulance services

solution takes too much time, I work on algorithms

As associate professor in the Algorithmics

solution for all users as a group, but for me

With many medical professionals in her family,

approaching that optimal solution in much less time.

group at TU Delft, Mathijs de Weerdt employs

it is not an optimal solution.’ In the long run,

Theresia van Essen’s childhood dream was to become

One could also simplify the model, of course, foralgorithms for solving problems involving

because of his algorithms, fewer gas and coal-a surgeon. But it is algorithmics with which she now

example by assuming average response times that are

multiple parties. In his current research, he

fired power stations may be needed to handle

helps to achieve optimal medical care. As assistantconstant throughout the day. But an optimal solution

develops algorithms for ensuring an efficient

network imbalances. His research is of bothprofessor in the Optimization group at TU Delft she forfor a simplified model might not be optimal for theand fair use of the electricity network. This

practical and scientific value. ‘When modellingexample investigates the optimal spread of emergency

real problem.’ Thanks to her algorithms, an additional

is of special importance now that supply anda real-world problem, we often encounter newcare ambulance services. ‘Healthcare is expensive,

dynamic ambulance post has been introduced in the

demand are less and less in sync due to thechallenges, such as a fair distribution. We

so any improvement in services, without increasing

Utrecht area, for a number of hours each day. As atransition towards renewable energy. ‘You

then take the structure of these problems into

cost, is more than welcome,’ Van Essen says. Because

result, the region now complies with the applicablecannot generate solar power at night, or windaccount to build faster and better solutions,’of increased computer power, this problem can now

regulations regarding the maximum response time.

power on a calm day,’ he says. ‘It helps if wehe explains. ‘This way, we build new algo­be addressed at a much more detailed level. ‘In the

It is unlikely for the additional ambulance post to be

only charge our electric car and turn on ourrithms containing components of existing

Netherlands, our level of detail is down to the numericcancelled anytime soon. ‘The number of incidents inelectric boiler at moments of sufficient supply.’algorithms. We then show that our newpart of the postal codes. We take into account thea region will only vary slowly over the course of years,’

Furthermore, there are capacity constraints

approach may be more widely applicable.’current spread of emergency ambulances and their

Van Essen explains. ‘It is, however, still advisable towithin the electricity network. In theory, thishistoric response times, for example.’ The starting

rerun the algorithm each year, to see if a substantial

can all be addressed by offering a financial

point of her research is to find an optimal solution forimprovement in emergency ambulance care can be

incentive to parties that would like to supply

the highest level of detail. ‘If determining the optimalachieved after all.’or use electricity at peak moments. The
magnitude of the incentive depends on how
strong a need each party expresses. ‘This only
works when the optimal solution is found,each time,’ explains de Weerdt. ‘Otherwise,
users can abuse the system by expressing‘Our aim is tostimulate diverse
behaviour in the user.’a fake need.’ As an optimal solution isrequired, de Weerdt does not use Machine
Learning. He also insists for the solution to
be a fair one. ‘It is not fair to always cut off

Emily Sullivan

the same neighbourhood or windmill park in‘Thanks to increased computing
power, we can use much
more detail when optimising
the spread of emergency
ambulances.’
Theresia van Essen

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Emily Sullivan

Peter Bosman

Diversity in recommendations

Optimal radiotherapy

Emily Sullivan is a postdoc in the Web Information Systems group at the TU Delft, where she
works on improving so-called recommender systems. These systems generate recommen­
dations, based on the movies you have watched or news article you have read on a website,
for example. ‘We try to increase the diversity in these recommendations,’ Sullivan says.
‘If the recommendations are too similar to your preferences, you may end up in the well-known
filter bubble. But if they are too dissimilar, you will ignore them out of hand. It is important forrecommendations to be diverse, but not too diverse. If a certain user is known for only reading
short news articles, you may want to recommend short news articles about slightly differing
topics.’ Sullivan uses existing Natural Language Processing software, a kind of artificial

Peter Bosman is part-time professor in
Evolutionary Algorithms at the TU Delft, andsenior re­searcher in Life Sciences and Health at
the Centrum Wiskunde & Informatica (Centre forMathematics and Informatics) in Amsterdam.
Evolutionary algorithms are his specialty, boththeir fundamental structure and their practicalapplication. He, for example, applies them in theintelligence, to extract linguistic features from texts. ‘In our research, we use various methods
to weigh these features in order to reorder the list of recommendations. Our ultimate aim is tostimulate diverse behaviour in the user.’ Another part of their research is focussed on the best
way to present the resulting list of recommendations to the user. The recommendations may,for example, be accompanied by an explanation such as: ‘If you are interested in a more indepth understanding of this topic, you may like these articles’. ‘In our group, we are not so muchinterested in the commercial application of this research,’ Sullivan says. ‘Rather, we want therecommender system to represent the norms and values of both the user and the company.’‘We provide radiation-oncologists
with a unique understanding of
the competing requirements in theradiation treatment of cancer. ’Peter Bosman

field of brachy­therapy, a cancer treatment in which'If the recommendations are too similar to your preferences,
you may end up in the well-known filter bubble.'radiation is applied from within the patient. ‘It is
often not possible to deliver the required amountof radiation to the tumour for the patient to be
cured, while also limiting the amount of radiation tosurrounding healthy organs in order to limit the risk of treatment related complications,’ Bosman
explains. ‘Using our algorithms, the treating radiation oncologist gains a unique understandingof how these competing requirements can be balanced for each particular patient. Being theexpert, they can then select the optimal radiation treatment plan for each patient, based onthese insights.’ It is important for the selected treatment plan to be deliverable from a technicalperspective and for it to be an accurate representation of reality. ‘We basically refrain from apply­
ing simplifications to the underlying model,’ says Bosman. In order to find a suitable solution inlimited time, the evolutionary algorithm tries several possible solutions at once. Through a process
mimicking natural selection, the algorithm will combine the good features of these solutions into
ever better solutions. A close collaboration with radiation oncologists is important for the results
to be useful in the clinic. ‘Our understanding of their underlying goals in the radiation treatment
allows us to build an algorithm that calculates the desired collection of applicable treat­ment
plans,’ Bosman says. ‘These plans are sometimes radically different from what they are used to.
It prompts them to reconsider the treatment plan qualities they find most important.’
Evolutionary algorithms are a kind of artificial intelligence introduced in the ’70s. Nowadays, it isrelatively easy for anyone to apply them but, Bosman stresses, ‘they certainly are not a cure forall. Thanks to our fundamental understanding of these algorithms we are much more likely tofind a good solution. For me, it is essential to combine fundamental research with its practicalapplication.’

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05
Algorithms unravel cellular
dynamics, and what itmeans for targeted therapy
Text: Merel Engelsman | Photography: Mark Prins

Modern technology allows us to monitor the activity of tens of
thousands of genes in cells. But to understand how cells work,
it is essential to determine how these genes interact with eachother over time to carry out vital functions or adapt to changes
in the environment. Novel algorithms, designed at TU Delft,
uncover the fundamental building blocks of cellular processes
in health and disease, and could help identify new targets fortherapy along the way.

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It’s about time

modules with arbitrary ‘jumps’ in time. At best

‘I have been intrigued by the paradigm ofthese are difficult to interpret and at worst

analysing biological systems through the eyes

they are not realistic. ‘The information is inof modularity for some time,’ says Gonçalves.

the data,’ Gonçalves says, ‘but it needs to be‘Cells organising themselves into organs inproperly treated and interpreted. We needed toliving organisms is an example of modularity

develop new algorithms to do this, algorithms

as a structural concept, in which modules arethat are time-aware and able to detect local

physical building blocks. In this sense, you

temporal patterns.’

can also think of words forming sentencesin text and pixels forming objects in images.
But modularity exists in function as well, suchas when genes and proteins show concerted
activity to perform biological tasks.’ Animportant aspect of functional modularity isthat it takes place over time. To understandthe dynamics of cellular processes, the‘We use the properties of time todesign efficient computational
methods for the analysis of timecourse data.’

researchers analyse gene activity data
Joana de Pinho Gonçalves: ‘We study
gene regulation and disruptions
involved in cancer to identify driversof the disease beyond genomic
variation and discover new targets fortreatment.’‘As computer scientists we bring a fresh
unbiased perspective to the study of biology.’

measured over multiple points in time. Modern
technology can do this for all genes in thecells simultaneously. The goal is to look forgroups of genes showing similar activity,

UDDNNNUUUD

as an indication of functional similarity.

Another challenge is that it would not be

One of the challenges is that the number offeasible to try out all possible sets of timefunctional modules and the duration of thepoints and search through all possible

biological tasks they perform are unknown

combinations of genes into modules of all

beforehand. ‘Most available approaches,

possible sizes. Depending on the size of thesuch as traditional clustering methods, group

dataset, this could take forever. ‘Instead,genes by looking at activity patterns over all

we take advantage of the properties of time

time points,’ Gonçalves says. ‘This is ideal

to apply useful algorithmic techniques,’

Organs, such as the heart and lungs, areworker molecules (proteins). Very often,

for detecting genes involved in more general

Gonçalves explains. ‘The fact that time has

the building blocks of the human body.

complex biological responses are the result

biological processes, but not so much to breaka strict chrono­logical order enables us to

The organs themselves consist of manyof multiple groups of genes working in con-down the more localised coordination often

establish a direction along which the searchcells, working together, enabling organs tocert over time, with each group performing

found in adaptive responses. First responder

should be performed. Likewise, knowing that

perform the tasks needed to help the bodysmaller well-defined tasks. ‘These groups ofgenes, for instance, are triggered in the

biological processes are expected to occur

function and respond to changes in its en-

genes can be seen as functional modules,’beginning but may not continue to coordinate

within a time window allows us to impose

vironment. Another process of cooperation

says Joana Gonçalves, assistant professor

as the response progresses into later stages.

a reasonable restriction on finding modules

is going on at an even smaller scale, within

at TU Delft’s Faculty of EEMCS. ‘They may

When we require high similarity over the entire

with consecutive time points.’ Perhaps thethe cells themselves. Whenever a cell has

differ between cell types, as well as between

time course, we will likely miss these effects.’

most important aspect of the researchers’

to respond to changes in its environment,

healthy and diseased cells. We develop al-

Methods that can search for local patterns,

approach is that they look at the shape of

certain genes will increase or decrease theirgorithms to reveal these functional modules,

however, are typically not designed for time

the gene activity pattern, rather than theactivity on demand to produce the necessary

and their differences.’series data. They can generate functional

exact values. For instance, if the activity

362020 | EEMCS NODES VOLUME II

37

value of two genes increases three-fold at

criteria,’ Gonçalves explains. ‘We take intoa certain point in time, this could be con­account the likelihood of finding eachsidered a match regardless of what theirfunctional module by chance based on its

baseline and final activity levels were. To

pattern, number of genes and number ofanalyse the data, the researchers therefore

time points. For instance, we look at how

determine if the change in the activity ofoften ‘up,’ ‘down’ and ‘no change’ occur

each gene between every consecutive pairwithin the pattern of a particular functionalof time points is either going up (U), down

module, compared to their prevalence in(D), or not changing (N), based on the slope

the entire dataset.’ These are purely data-of the change. ‘This is one among many

driven criteria, independent of biologicalpossible discretization options that can beknowledge and meaning. Using biologicalused,’ Gonçalves says. ‘Translating genedatabases, the researchers can also assess

activity values into letters allows us to apply

the consistency in the biological role ofefficient string-matching techniques to findthe genes in each functional module. ‘We

maximum-sized modules which are notmake use of these and other statistics tofully contained by any others.’ The observed

filter and rank modules, in order to selectstring patterns have to match exactly, suchthe most promising candidates for furtheras ‘UDDNNNUUUD,’ but the discretization

experimental validation.’‘Our algorithms open new avenues towards
targeted therapy by uncovering groups of genes
working in concert, and the regulators controllingthese processes.’

allows for some small fluctuation in theoriginal values which makes the techniquerobust to noise. The researchers’ most recent
algorithm allows these patterns to be shiftedin time to account for cases in which genes
within a functional module may be activatedor inhibited with a certain delay. Because of
the algorithmic design strategies employed,
the LateBiclustering algorithm can be run
comfortably on a personal computer for
most available time course gene expression
datasets.

Refining modules
One of the pitfalls with algorithms ofa combina­torial nature is that they cangenerate a lot of results. ‘We develop
strategies to select the best functional
modules, according to different statistical

38

Back to biology
The researchers started off using publicly
available measured data for a proof ofconcept. For experimental validation,
they worked in close collaboration withbiomedical researchers at the Netherlands
Cancer Institute (NKI). ‘Since the genes infunctional modules show similar responses,
our idea was that they might be controlled

About Joanaby the same regulators,’ Gonçalves explains.

Joana Gonçalves, assistant

Regulators are very interesting from a bio­

professor at TU Delft’s Faculty

logical perspective, because they controlof EEMCS

which genes are expressed and at whatrates. They are a step up in the organizational
hierarchy of cellular processes, somewhat
like managers supervising collections ofgenes. ‘We identified these regulators using
an approach I published during my PhD, andwhich I then used in combination with our2020 | EEMCS NODES VOLUME II

39

‘These algorithms will allow us to discover
more robust patterns’

time-aware LateBiclustering algorithm.’ The

and development, disease susceptibility

provide a promising step in this direction,’example identify functional modules that are

researchers used this methodology to analyseand progression, or response to treatment.

Gonçalves says. ‘By revealing how genes in

disrupted exclusively in cancer cells and not

the response of human prostate cancer cells

Although there are still many steps to takeprostate cancer cells organise in response

in healthy cells. This can then be exploited

to androgens (male hormones). A number

before the proverbial ‘cure for cancer’ isto androgens, we can help understand which

therapeutically,’ Gonçalves says. ‘Or we mayof these identified regulators were inhibited

found, the idea is that these newly developed

functional modules or biological mechanisms

find functional modules that show distinct

during subsequent validation experiments.

techniques will be able to contribute toinfluence disease progression. Regulators ofpatterns of activity in subgroups of patients.

Their inhibition indeed resulted in consistentidentifying new drug targets for therapy.

such mechanisms are especially appealing

Based on this information, these subgroupschanges in gene activity in the functional

Consider prostate cancer, for example, aas drug targets, since it may be easier tomay be suitable for alternative treatment

modules that the regulators were predicted tohormone-related cancer that is strongly

target a single regulator rather than trying

strategies.’ So far, the researchers havecontrol. ‘Together with our collaborators, we

influenced by androgens. The standard

to directly control all the genes within an

looked into model systems such as cancer

showed that our algorithms have the ability

treatment blocks the binding of androgens toimportant functional module.’cell lines, which are far more homogeneous

to capture meaningful biological knowledge,’

the androgen receptor gene, which is a known

Gonçalves says.

master regulator of the androgen response.

One of the next steps of the researchers is

According to Gonçalves, ‘an important

In many patients, however, the cancer cells

to develop algorithms to identify functional

challenge in drug development is to translate

develop resistance to this treatment.

modules across multiple samples. Thinkthe knowledge we acquire from such modelof cells from different tissues, different

systems to actual patient tumours.’

Targeted therapy
The analysis of gene activity over time isthan cells found in patient tumours.

critical to advance our understanding of

It is therefore important to identify new

patients or different regions within the same

complex biological mechanisms involved inalternative targets for treatment of thistumour. ‘These algorithms will allow us

processes such as normal human growthcancer. ‘We have shown that our algorithms

to discover more robust patterns, and for40

A fresh perspective

about the experimental techniques and the biologicalAs she had contemplated studying medicine, biology

systems under study,’ Gonçalves says. ‘They draw

was one of the courses Gonçalves followed in

hypotheses and interpret observations in light ofhigh school. She chose to study computer science

existing knowledge. As computer scientists, with far

instead. Nearing the end of her studies, it turned

less prior information, we offer a complementaryout that the algorithmics professor she chose

perspective. We typically conduct unbiased dataas her thesis supervisor worked on answering

analyses, see interesting patterns emerge, and thenbiological questions. Since then, bioinformatics

start asking questions. It is a fresh approach to thehas been her focus. Coming from such different

study of biological systems, sometimes leading tobackgrounds, it sometimes takes a bit of effort for

surprising findings.’ Gonçalves maintains active links

biologists and computer scientists to understandwith the NKI, and is working on joint grant proposals

each other. But working together allows them toto expand the collaborations in a number of research

go well beyond what they would be able to achieve

directions together with groups at LUMC andon their own. ‘Biologists have in depth knowledge

Erasmus MC.

2020 | EEMCS NODES VOLUME II

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Increased road safety withhigh-resolution automotive radar

06

Text: Merel Engelsman | Photography: Mark Prins

A step reduction in fatal road accidents. Whether it is by means offully autonomous cars or the widespread introduction of advanced
driver assistance systems, Professor Vaucher works on automotive
radar technology for improved road safety. Equipped with millimetre
wave radar, cars will be transformed into securely-connected robots
with the capability of sensing the environment, thinking, and acting
autonomously.
‘Companies such as Waymo and Tesla, working on fully autonomous cars, get all the media
attention,’ says Cicero Vaucher, professor of integrated millimetre wave front-end systems at
the Electronics Research Laboratory within the Faculty of EEMCS. ‘But full autonomy is only thelast phase in a continuous process towards increased road safety, achieved bytransferring more and more responsibility from the human driver to the car. This

‘Road fatalities in
the Netherlands
peaked in the ’70s
at 3500 casualties
per year.’process started about five years ago and is now really taking off.’ Road fatalities
in the Netherlands peaked in the ’70s at 3500 casualties per year. It was theintroduction of seatbelts, followed by legislation making them mandatory, that
initiated a steep decline. Thanks to the subsequent introduction of electronics
systems, such as the anti-lock braking system (ABS), the airbag and car stability
systems, the number of fatalities has continued to decline. ‘After initially being
luxury accessories, these systems are now mandatory as well,’ says Vaucher.
‘Within the next three years, I expect currently optional radar-based technology,
such as adaptive cruise control and automatic emergency breaking, to also

become compulsory. And this is only the first step towards increased road safety and highly
automated driving that automotive radar will help enable.’

Not yet ready for full autonomy
In this first level, the car can control steering or vehicle speed, with the human driver controllingthese as well. As a society, we are already adopting the second level as well, in which control
of both steering and speed is fully transferred to the car under specific circumstances, suchas partially automated parking or driving assistance in a traffic jam. There even are companies
offering the semi-autonomous third level of fully automated highway driving and self-parking, forwhich complete control is transferred to the car. ‘Up to this level of automation, the human driverstill carries overall responsibility for safe operation under all conditions,’ Vaucher explains. ‘The

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driver therefore has to remain alert at all times.’ The fourth andfinal level, of fully autonomous driving across many driving

SCAN!

modes – in which the driver can read, work or relax while being
driven – is not yet commercially available. ‘The industry is not
yet up to that level,’ says Vaucher, ‘and legislation needs tocatch up. An alert and responsive driver is still legally required.’
For all levels of automation to become widely adopted, andthen mandatory, it is important that the underlying technology
is affordable. Lower levels of vehicle automation may require
only a handful of radars pointing forward, but for the highest
levels the car may need to be equipped with up to twenty
radars covering all horizontal directions. ‘We have now reached
the point where the hardware costs for such an advanced

Inaugural speech Cicero Vaucher.

radar system are well below a thousand euros,’ Vaucher says.
‘For high-end segment cars this is an acceptable price level,
whereas a further decrease would be welcome for cars in theentry-level segment.’

Smaller than a passport photo
Automotive radar uses a so-called chirping signal, in which thefrequency of the emitted radar signal increases linearly overtime. This chirp is repeated tens of thousands of times eachsecond, with a brief pause between each pulse. It allows forboth the distance to and speed of objects to be determinedwithin milliseconds, by comparing the frequency of the returned
radar signals to the (then) emitted frequency. ‘Current automotive radar systems use very high frequency radio signals witha wavelength of only a few millimetres,’ Vaucher explains. ‘The
three-fold reduction in wavelength compared to earlier systems,
in combination with an increased bandwidth at these higher
frequencies, comes with plenty of benefits. It has resulted ina much better resolution in both the measured range and velocity, while also enabling a substantial reduction in the size andenergy consumption of the radar.’He shows the current state of the art in automotive radar,

About Cicero
Cicero Vaucher, professor of
integrated millimetre wave frontend systems at the Electronics
Research Laboratory within the
Faculty of EEMCS.

developed by himself and his team at NXP Semiconductors.
The complete radar system consists of two tiny chips, threeradar emitters and four radar receivers, all on an integrated
circuit board smaller than a passport photo. ‘It can be inte­
grated invisibly, even into small cars,’ Vaucher says. ‘This single
solution can be used for all levels of vehicle automation. The
difficulty with millimetre radio waves is to have the technology
to reach those frequencies. But once you get there, it is a hugeresource to be used.’44

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45‘Adding affordable millimetre wave radar technology to all cars
improves road safety and reduces road fatalities significantly.’

Using the passport-photo-sized chip ‘asis,’ an angular resolution of 36 degrees canbe achieved, basically subdividing humanforward vision into only five pixels. ‘It will beable to detect an oncoming truck, but not the
motorcycle that may be overtaking it.’

Unaffected by weather
Radar alone is not the solution. Multiple technologies are driving the process
towards increased car autonomy and road safety, with each technology having
its own strengths and weaknesses. ‘I believe that radar and cameras are ideal
complementary sensors,’ says Vaucher. ‘A camera has a very high resolution
for detecting objects, but it has difficulty assessing their distance and relative
speed.
That is exactly what radar is ideally suited for. Radar, on the other hand, cannot
read road signs, see markings on the road such as lane lines, or determine thecolour of traffic lights or tail lights. Then again, radar performance is not affected by fog, heavy rain, or nightfall.’ The functionality of both systems over­laps
with the LiDAR system (Light Detection And Ranging) that is frequently used in
car automation. It is typically placed on top of the car for an all-around field ofview. Using a rotating laser, it emits millions of infrared light pulses per second.
By measuring the time it takes for each pulse to return, it creates an image of its
surroundings, with quite a high resolution. Some of these systems can even determine the velocity of what they see, but they are expensive, and their relia­bility
is unproven. ‘More importantly, it is not only about complementarity,’ Vaucher
explains. ‘The more responsibility you transfer to the car, the more redundancy
you want to build into your system.’ Having duplicate functionality means thatthe car will still operate safely, even if a certain sub-system breaks down. ‘We dowant to increase the angular resolution of automotive radar to the point where
it could replace LiDAR,’ Vaucher continues, ‘but it would then be up to the car
manufacturer to decide on the required level of redundancy. Perhaps it is best
to have both LiDAR and radar.’
Having duplicate functionality
means that the car will still
operate safely, even if a certain
sub-system breaks down.

*MIMO
By using multiple transmitters at
the same time, we get the threefold increase. This is then called
multiple-input multiple-output
technique (MIMO). The multipleinput refers to several receivers,
whereas the multiple-output
refers to several transmitters

46

The CRUISE project

Tackling interference

Improving angular resolution is one of the challenges

Automotive radar sensors share a limited frequency

addressed in the CRUISE project, a research collabo­

bandwidth. Interference will therefore increase evenration between TU Delft and NXP Semiconductors.

further as radars are integrated into more and more

Vaucher is employed at both. He explains that ‘thecars. This may result in objects with a low radar cross-project addresses challenges that we know are

section to be lost during tracking or not to be detected

coming. We can, for example, already anticipate theat all, leading to dangerous traffic situations. ‘This

need for radar systems where you make measure­

may even become a blocking point for autonomous

ments with several transmitters at the same time.’

driving initiatives,’ Vaucher explains. ‘Within the

Using the passport-photo-sized chip ‘as is,’ an angular

CRUISE project we investigate novel approaches toresolution of 36 degrees can be achieved, basicallytackle these interference issues. We are looking into

subdividing human forward vision into only five pixels.

separating the signals by coding them, for example.’‘It will be able to detect an oncoming truck, but not the

Not even the powerful linear chirping signal itself is

motorcycle that may be overtaking it,’ Vaucher says.

sacred in the quest to tackle interference and to realise‘Using the innovative antenna layout in combination

high-resolution affordable radar. ‘We work in closewith smart digital signal processing, however, a three­collaboration with experts in radar signal processing at

fold increase in image resolution can be achieved

TU Delft, such as Professor Yarovoy from the group of

by a process called (MIMO*) beamforming.’ For theMicrowave Sensing, Signals and Systems. Our aim is

overtaking motorcycle to be detected the angular

to determine the next chirp wave-form, one that would

resolution of the radar needs to be improved anotherbe less susceptible to other radars or self-interference.

ten times, down to a single degree. ‘We know how

At the Electronics Research Laboratory, we have theto get there, and even beyond, by assembling fourknowledge and means to then develop the circuits thatof these radar chips into a single printed circuit

will be able to generate and decipher these signals.

board. The difficulty is to get everything working

Automotive radar is a very exciting multidisciplinary

simultaneously as the transmission channels willproblem and it is really important to close the loop ofinterfere with each other.’circuit design and signal processing.’

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‘In autonomous vehicles, complementary sensor redundancy is
crucial. Duplicate functionality of radar and lidar sensors means
the car can still operate safely, even if a certain sub-system
breaks down.’

Despite rapid developments in sensor technology andartificial intelligence, it still is a long road towards fullyautonomous cars.

Sensor fusion for optimal use of radar images
There are even more disciplines needed, as the processed signals also need to be interpreted.
There is a lot of information coming from the radar; the distance towards many objects, theirrelative speed and at what angle they are located with respect to the car, but it doesn’t tell you
what each object is. The artificial intelligence used to interpret the images produced by on-car
cameras will very likely also be needed for processing radar images. ‘More importantly,’ Vaucher
says, ‘different sensors need to be joined for optimal decision making. A camera might classify
an object to be a pedestrian, but the radar could perhaps recognize the variety in relative speed
patterns of legs and torso to be typical for a cyclist, or even for something else.’

A long road towards fully autonomous cars
Despite rapid developments in sensor technology and artificial intelligence, it still is a long road

Millimetre wave radio signals

towards fully autonomous cars. They are already being extensively tested on the road and even

Millimetre waves are radio waves and, just like visible light, part of the electromagnetic

within cities in the United States but, according to Professor Vaucher, it may still take a few

spectrum. As all electromagnetic waves travel at the constant speed of light (of roughly

years for them to become commercially available. ‘The infrastructure in these cities, consisting

300,000 kilometres per second), it is the frequency of these waves that determinesof broad roads and having only few pedestrians and virtually no cyclists, is almost ideally suited

their wavelength. Radio waves with a frequency between 30 GHz to 300 GHz (1 GHz =for initial technological development and later for commercial introduction,’ he says. ‘But it is

1 gigahertz = one billion oscillations per second), have a wavelength of 10 millimetresa much bigger challenge for autonomous cars to navigate Delft city centre, where you have to(1 centimetre) and 1 millimetre, respectively. Visible light has a wavelength that is about

deal with ten pedestrians and fifteen cyclists simultaneously.’ Not to mention a plethora of small

ten thousand times smaller.

bridges, frequent changes in traffic situations and the erratic non-law-abiding behaviour of said
pedestrians and cyclists. Asked if he will be one of the first owners of a fully autonomous car,Professor Vaucher responds that ‘it is fascinating technology and it will represent a major step
forward in road safety. I am looking forward to it.’48

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07
You only know the best method of
defence when you understand more
about your opponent
Text: Robert Visscher | Photography: Mark Prins

Christian Doerr conducts research into cyber threat intelligence
and also devises ways of preventing new attacks.

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Your research field is digital security andyou and your team explore how cybercriminals operate. Why is this necessary?

About Christian
Christian Doerr is a professor in Cyber Security
and Enterprise Security at the Hasso Plattner‘ICT plays a huge role in our society. It ensures

Institute. Before he made the move to Potsdam

that we have water to drink, that there is food in(Germany), he worked as an assistant professor

the supermarkets and that electricity is available

in the Cyber Threat Intelligence Lab in thefrom the wall socket. All of this runs faultlesslyIntelligent Systems department of EEMCS.

because almost everything is digitised. But we

Because he is still a guest lecturer at TU Delft,have become so dependent on ICT that it’s also

you see him walking around the university

making us vulnerable. Imagine someone wants

campus on a regular basis. About his field of

to do harm and attack an electricity plant or

research: ‘I work in the broad area of network

our water supply. We would be facing a major
problem.’security and critical infrastructure protection.

Why are these ICT systems so vulnerable?

systems, localizing and estimating current

Because many of the innovations we are now

threats through real-time situational awareness

My research focus is designing resilient networkin networks as well as conducting threatusing were originally designed for anotherintelligence on adversaries. Prior to joining,

purpose. The internet is the best example of this.

I was at the University of Colorado, USA, where

It was devised as a network between computers

I received my PhD in Computer Science andthat could trust each other. This means that

Cognitive Science. While most of my work

security was not built in at the design stage. No

focuses on technology, I also integrate socio-

one predicted that we would use it to connect

technical aspects of cyber security with this

together so many computers, in a situation inbackground in my research.’which not every user can be trusted. Besides, it’salways much more difficult to integrate security
retrospectively. It should have been thought ofmuch earlier in the design process. Unfortunately,
that’s often far from being the case.

How can you defend yourself against cyber attacks?
First of all, you need to know what an attacker is doing. Imagine someone breaks in to yourneighbour’s house. You don’t want it also happening to you. It’s likely that you’ll head to the DIY
store and buy an extra lock. But by doing so, you’re assuming that the burglars will come throughthe front door. They may however throw a brick through the window or the criminal could have apasskey to open all locks. You only know the best method of defence when you understand more
about your opponent. Because if your neighbour had a brick thrown through the window, you may
be better advised to invest in some bars for the downstairs windows.

Christian Doerr: ‘I was mad about computers as a young
boy. I found it amazing to see how a computer sends
information and it suddenly appears somewhere else via
a cable. It’s almost like magic!’

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You recently conducted research into how
hackers operate by looking at attacks on
TU Delft. What did you find?
Our discoveries included an attack by 27,000
computers all targeting TU Delft. These computerscome from more than a hundred countries. They

‘Our discoveries included an attackby 27,000 computers all targeting
TU Delft. These computers comefrom more than a hundred countries.’transmit information intermittently. There may be justa few hours in-between, and then several days. It justlooks like random noise, but when you put it together,
defend ourselves more effectively. You can’t stop it,

Are companies actually willing to share
information with each other?

but it can be blocked.

They can sometimes be concerned that competitors

it’s a coordinated attack. Noticing this enables us to

Obviously, in the future, you will also want tostop this kind of attack.
How do you do that?
‘We are now working on a tool that not only monitors if something is going wrong,but also assesses how serious it is.’will see who they are doing business with or what
they’re planning for the future. This deters them fromshowing other companies in the same sector what
type of e-mails they are receiving from hackers, for

One of my students is researching this. It is all about

example if they’re pretending to be customers. There iswhether we can predict what an attacker will do. If hea solution for that. There are already ways of securing

first tries this door to see if he can enter, we know thate-mail while still informing others that it may involve an

he’ll move on to another door after that. You therefore

attempted hack.

install a firewall. Even better is when we put a so-

Is that how it also works in your field of cyberthreat intelligence?

What do you learn from analysing criminals?
We are working with a major telecom provider on

the attacker in an environment we control. This means

How do you encourage a corporate culture inwhich employees share information?

Understanding how criminals operate is an importanta project. The internet is all made up of networks

it’s not damaging to our system and we can see what

By offering extra training to make them aware ofpart of my work. What skills do they have and how doconnected to each other. Providers ensure that these

the person is doing in the honeypot. The problem

threats and security. You need to reward an employee

they apply them? Have you been targeted by a criminal

connections happen and an important part of thatis that advanced attackers, who worry us the most,

who reports a phishing e-mail. The IT helpdesk thensending out phishing e-mails in the hope that someone

involves the so-called BGP. This Border Gateway

have techniques that tell them they are in a honeypot.

sends round an e-mail praising the employee andclicks on a fraudulent link? If so, you’re a random victim.

Protocol ensures that different networks are connected

They then share that information with others. We are

warning the others. You should arrange free cake for

But if you have a Picasso painting on your wall at

to each other by exchanging information about

currently doing a study to test how they discover this.

everyone in the staff restaurant. That makes it a talking

home and a burglar tries to steal it, you’re dealing withaccessibility. It is the glue that holds together all theInterestingly, attackers are often better at sharing

point and rewards good behaviour. People are always

a different approach. That person will do everything

networks, so to speak. Criminals can attack the BGP

information with each other than we defenders are.

the weakest link. We shouldn’t blame them, but enlist

possible to break in and you need to protect yourself

in a way that causes internet traffic to be redirectedaccordingly. It’s a different threat profile. It also works

to them. Currently, we are already monitoring whether

like this with cyber threats, for example if a company

something strange is happening, but we do not yet

Why is it so important for companies to share
information with each other?

has important corporate secrets. We investigate how

know what exactly is going on.

It enables them to warn one another. For example,

I was mad about computers as a young boy. I found it

attackers may be specifically targeting several banks

amazing to see how a computer sends information andor the transport sector. Research shows that criminals

it suddenly appears somewhere else via a cable. It’s

often attack many companies in a specific sector

almost like magic! When I started studying, I became

the attackers operate and how you protect against that.

called honeypot in that place, enabling us to capture

their help instead.

Why are you so fascinated by your specialist field?

a crowbar to break in but never throws a brick throughOf course, you will want to find that out. How do
you approach that in practice?

the window, you will take that into account in the

We are now working on a tool that not only monitors

simultaneously. They also often try out attacks inmore interested in security and how attackers operate.

protection. Our work is similar to that.

if something is going wrong, but also assesses how

Germany and France first before moving onto smaller

How do you send data securely? As we have become

serious it is. For example, our algorithm may notice ancountries, such as the Netherlands and Belgium. If

ever more dependent on computers, this field of

attack on a bank that has already been tried on three

German companies have already shared information

work, still in its infancy, has only become even moreother banks and it’s targeting accounts in Western

about a phishing e-mail or hack with Dutch companies,

important. I hope that I can do my bit to combating theEurope.

the chance of them falling for it is much lower.

cyber threat.

If, for example, you discover that someone always uses

‘Our algorithm may notice anattack on a bank that has alreadybeen tried on three other banks.’

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08

Protecting the electricity
grid of the future
Text: Merijn van Nuland | Photography: Mark Prins‘Transport chaos across England and Wales after major power cuts’, ‘Huge power
cut paralyses Britain’, and ‘Urgent investigation at National Grid after worst power
cuts in decade’ – the headlines in the Guardian, Daily Mail and Sunday Times
did not mince their words when large parts of the UK were hit by a major power
failure in August 2019. Millions of households were without electricity, no trains
were running, and the roads became dangerous because the traffic lights failed.
A generator tripped off because of a fault, and as a result, less electricity was

Power failures occur in all shapes and sizes. At TU Delft,being supplied than used.

scientists conduct research on these kinds of incidents and

It is just one example of what can happen when the electricity grid is affected

search for solutions how to make the electricity grid more robust

by severe disturbances, according to Marjan Popov, associate professor inin the future. One of them, Associate Professor Marjan Popov,

Electrical Power Systems at TU Delft. He and his team are working on finding
solutions for rapid detection of failures and providing suitable protection against

has set up the Power System Protection Centre at TU Delft

power outages. That is, as yet, far from simple, because a power outage canto facilitate a smooth transition to renewable energy. Using

have various causes, from a faulty generator to a lightning strike and fromexperiences from recent black-outs, he explains what can gowrong.

‘A power outage
can have various
causes, from afaulty generator
to a lightning
strike and frombroken cables toan imbalance inpower production.’

broken cables to an imbalance in power production. In recent months, Popovand his team completed two projects that can contribute to a more stable androbust electricity grid. The main aim of both projects was the early detection andelimination of short circuits in the network, in order to prevent a domino effect.

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‘With a reliability level of 99.9948%,
the Netherlands secures power supply
almost at all times.’

Marjan Popov: ‘The electricity grid will become more
complex after the transition to renewable energy, much
more complex than most of us would imagine.’

Ridiculous mistakea handful of coal-powered plants to thousands of windThis is the reason that Popov set up the Power‘In my projects – called MIGRATE and URSES – I am

parks and solar panels will make the grid susceptible

System Protection Centre, a TU Delft collaboration

looking for a way to monitor an electricity grid,’ says

to disruption.

with the Dutch grid operators TenneT, Alliander

Popov. ‘We used big data research to identify theand Stedin, and the companies General Electric

weaknesses in the system, so that we could isolate

It is in the nature of the new phenomena that makes

and Siemens. TU Delft already has everythingthese components from the rest of the grid. Ansuch a difference. In a ‘green’ electricity grid, fault

that is needed for leading research in this field.

electricity grid can be compared to the human body:currents are usually with lower amplitude and

The existing Real-Time Digital Simulator and the

because everything is connected, and components

contain higher harmonics, and as such they may

future Electrical Sustainable Power Lab put TU

which are linked together can easily affect each other.’

have a negative effect on the efficiency of the grid.

Delft in the perfect position to study the challenges

In addition, renewable sources have little to noof the future in all their facets, and Popov will

The fact that this can be dangerous was shown in Italy

inertia, which means that future electricity grids willundoubtedly continue to play an important role.

in 2003. Some 17 years later, Popov still speaks withbe less stable than coal-powered plants. All theseamazement about the ridiculous mistake that resulted

disturbances are very difficult to detect by applying

Lightning remains unpredictablein one of the greatest ever power failures in European

classical protection.

So, have Popov and his team now tackled alltypes of power failures? No, not yet. As it turns

history. At the time, Italy imported power from France
and Switzerland. But when the Italians decided to‘In the past six years, my team and I have made a lotout, scientists are still unable to cope enough with

import more power from Switzerland, this provedof progress in this complex research field,’ says Popov.

lightning strikes. In its search for earth, lightning

to be too much for the Swiss power cables. It was‘We have developed an efficient new algorithm andusually strikes tall objects, such as electricity

not long before the first connections failed. Italy

protection platform in the MIGRATE project, which can

towers. Of course, these are well protected by

was without power for 24 hours, costing the country

detect power outages and immediately isolate affec-

lightning conductors and other mechanisms,

billions of euros. Only the inhabitants of Sardinia

ted parts of the system. In the NWO-URSES project,

but lightning still regularly strikes transformers

were unaffected. A domino effect could have also left

we have created a new platform for collecting data in

as well. For example, in June 2012 it happened

other European countries in darkness if Italy had notreal time, which allows us to measure voltages andin Nieuwegein when a lighting hit a transformer.

been quickly disconnected from the European power

currents; as a result, we can swiftly detect the ‘sick’

As many as 70% of residents – a total of 17,000

network in order to prevent the spread of the black out.

part of the grid and isolate it.’households – were without electricity for almost

Renewable energy puts the catamongst the pigeonsPower System Protection Centre

With a reliability level of 99.9948%, the Netherlands

the transition to renewable energy, much more com-secures power supply almost at all times. But,

plex than most of us would imagine,’ says Popov. ‘Asaccording to Popov, it is not inconceivable that the

we will be taking the large power plants out of operati-

electricity supply in the Netherlands could become

on, we will have to think about new ways of preventing

less reliable in the future. There is one key reason for

power cuts and electrical resonance. In other words,

this: the high utilization of renewable energy sources.

we must once again make our system immune to dis-earthing system. As part of the SINTEF project,Wind and solar power in particular are supposed toturbances. Therefore, we need to come up with reliable

I am developing a unique interface to demonstra-cause a sharp drop in CO2 emissions. However, totallyprotection solutions, and we need to do it soon.’

te how to design reliable protection.’‘The electricity grid will become more complex after

24 hours. This not only caused annoyance, but‘As it turns out,scientists arestill unable tocope enough withlightning strikes.’

also financial losses, resulting from shortageof electricity. This is not the only power outage
to have been caused by lightning. ‘There is no way
to predict the impact of lightning,’ says Popov.
‘In certain situations, the protection measures failtoo. To optimise this protection, we need research
into the interaction between lightning and therevamping the structure of an electricity grid from58

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09
Computer as a sheepdog
Text: Peter Baeten | Photography: Peter Baeten

Hybrid intelligence stimulates both human intelligence and thedevelopment of the artificial variant. Catholijn Jonker is a strong
advocate of this new vision. In other words: the computer asa sheepdog for humans.

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The question of what artificial intelligence is and what

In other words, it is essentially about building the bondComputer as co-author

problems it should solve has shifted with the passage of time.

between the computer and people, especially for the

Potential areas of application for hybrid intelligence

In the past, people were far better and faster at calculating

longer term. ‘Currently, for example, coaching systems

include healthcare, education and science. ‘A goodthan any machine. Since then, the problem of calculation has

work for a few weeks at most. But the interaction in

future example could be in my work as a scientist.

been totally solved by computers. But, quite aside from this, thea hybrid intelligence system needs to be able to adapt

You could imagine a scientist having a hybrid intelligent

mainstream approach in artificial intelligence (AI) has always

over a long period; and it needs to remain engaging andagent as a research assistant. This assistant would

focused on autonomous systems that can replace people

enthralling. This means that the development of hybrid

start by searching for what else has been publishedand human activities. ‘However, I see much more potential inintelligence will very much depend on knowledge fromabout a particular research subject, or checking if yourintelligent systems that collaborate with humans, can adapt toother disciplines, such as psychology.’

specific hypothesis has already been tested. The next
step would involve this kind of system in thinking aboutchanging circumstances and explain their actions. The idea isthat you make much greater progress by combining artificial

This is why it is particularly useful that Jonker not

your research strategy or even brainstorming with you

intelligence with human intelligence. This enables both of

only works at TU Delft (since 2006) but also at Leiden

about the subject. The ultimate consequence of thisthem, human and computer, to grow. Compare it to a sheepdog

University. Since 2017, she has also been a part-

would be that the agent would need to be credited asthat accentuates the sheep-herding capacities of a shepherd.

time professor at the Leiden Institute for Advanced

co-author of the scientific paper. But that’s still quite

We call that hybrid intelligence’, explains Catholijn Jonker,

Computer Science (LIACS). ‘This enables me to seesome way off, by the way.’ ‘I would be so bold as to say

professor of Interactive Intelligence at the Faculty of Electricalconnections with other disciplines, in a way that’s notthat this new approach makes us quite unique in theEngineering, Mathematics and Computer Science (EEMCS).

possible at TU Delft. Within hybrid intelligence, theseworld of artificial intelligence. Although other research

external connections are absolutely essential.’

programmes have touched on this vision, they haven’t

Gravitation programme

done it in the same way as we’re doing. This alsoThis radical basic idea was last year awarded funding by the

makes it difficult. Perhaps you could compare us toso-called Gravitation programme, financed by the Ministry of

Baron van Münchhausen: we’ll need to pull ourselves

Education, Culture and Science (OCW). This funding will enable

out of the swamp by the hair.’leading researchers to spend ten years working on fundamental
research and collaboration. The research proposal HybridIntelligence: Augmenting human intellect was awarded a totalof €19 million. Together with colleagues at Amsterdam’s Vrije
Universiteit (the main applicant), the University of Amsterdam,and the universities of Leiden, Utrecht and Groningen, Jonker
and her Delft-based Interactive Intelligence department will set
to work developing theory and methods for intelligent systems
that collaborate with humans. The aim is for these systems toenhance our strengths and compensate for our weaknesses.
Jonker: ‘In the Faculty of EEMCS, our main focus is on the dialogue between humans and machines, in which they each help

‘I think that the rise of artificial
intelligence will certainly havepainful consequences in many
individual cases and we need
to be vigilant about that.’each other by shining their own light on the shared challenge.
This means having the capability to explain your thoughts tothe other, and the social intelligence and ability to learn fromthat dialogue.’Social robot used for entertainmentor to stimulate physical activities

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The pocket negotiator is a good example of

In any case, the subject of artificial intelli­an AI development that has enjoyed years ofgence evokes all kinds of emotions, especiallysuccess. Jonker was awarded a Vici grant

among the general public. One recurringin 2007 for the project. Since then, a spin-off

fear is that artificial intelligence could makecompany (WeGain) has developed aroundenormous numbers of jobs surplus to

the technology and various customers are

requirements, resulting in very high levels

showing an interest. ‘It works in two ways.

of unemployment. What does Jonker think

On the one hand, the pocket negotiator helps

about that, as a scientist? ‘I think you needto think about your preferences for potential

to draw a distinction. Are you thinking aboutoutcomes in the negotiation. On the otherindividual cases or the fate of humanity in

hand, it’s now becoming possible to actually

general? For humanity as a whole, I actually

ask the pocket negotiator for advice during thethink there‘s nothing new under the sun, apartnegotiation itself.’

perhaps from the pace at which changes are
now happening. Jobs will certainly disappear,

Emotions

You could imagine a scientist having a hybrid intelligent agent as a research
assistant. This assistant would start by searching for what else has been
published about a particular research subject, or checking if your specifichypothesis has already been tested.

Ethics‘It basically comes down to not doing every-

If all goes well, the Gravitation programme willthing just because you can, which is an easy

not only deliver new scientific insights andtrap to fall into, especially in technology. If you

applications, but will also play a crucial role

don’t think carefully all the time, you eventuallyin the debate about artificial intelligence andhave no idea what it is you’re doing. And once

policy relating to ethics around AI. This subject

you’ve introduced a new technology, it’s veryof ethics touches on an essential point fordifficult to remove it from the system. Just

Jonker: ‘For example, I’m one of the founders

think about a problem like asbestos and howof the Delft Design for Values institute andlong we’ve been dealing with it.’

I’m also involved in that other programme thatreceived Gravitation funding: Ethics of socially

Pocket Negotiatordisruptive technologies (SDTs).’ New techno-

One area affected by an ethical issue was

logical advances, such as robotics, synthetic

the development of the so-called pocket

biology, nanomedicine, molecular biology andnegotiator: an AI system to support humanneurotechnology, but also artificial intelligen-negotiators. ‘I could have opted to equip thisce, all have potential to bring about major

negotiator with the ability to recommend lying

changes to day-to-day life, culturally, sociallya little; after all, that could have been usefuland economically. But they also raise complex

strategically, but I chose not to incorporate

moral issues that call for ethical reflection.

that option.’64

but others will replace them. That’s always

Ethical considerations are always an issue

what happened throughout history. I think thatin artificial intelligence, even in the very long

the rise of artificial intelligence will certainly

term. ‘For example, I sometimes think about

have painful consequences in many individual

the following dilemma: what happens if wecases and we need to be vigilant about that.

keep making everything easier for ourselves

What will the people who lose their jobs bethrough the development of AI? Would it makeable to do? AI might actually be able to help

us increasingly lazier and would that ultimately

in answering that question.’

become part of our DNA?’

SCAN!

‘What happens if we keep making everythingeasier for ourselves through the developmentof AI? Would it make us increasingly lazier
and would that ultimately become part of ourDNA?’

What is intelligence? A dog that can smell better and thus
serves us in hunting or in disaster areas, complements
human intelligence in a beautiful – symbiotic – way. Can
we look at computers like that? That's one of Professor
Catholijn Jonker's areas of expertise. In a conversation
with Jim Stolze, she talks about her research and how
TU Delft pays attention to the ethical aspects ofdatascience through Design for Values.

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Intermittent computing
to replace trillions ofbatteries

10

Text: Merel Engelsman | Photography: Mark Prins and C. Jason Brown

Few things change as fast as the future of computing. Most experts andlarge chip manufacturers agree that the world’s ever-increasing appetite forcomputing will culminate in an omnipresent Internet of Things – trillionsof devices taking sensor measurements, performing calculations andcommunicating with each other. Intermittent computing will not change that,
but it may transform how these devices are powered, changing their operation
at a fundamental level.

Warehouses full of dead batteries‘For a sustainableinternet of things,
batteries must beleft behind.’‘Batteries are the biggest threat to a sustainable Internet of Things, or tocomputing in general,’ says Przemysław Pawełczak, assistant professor in theEmbedded and Networked Systems Group at TU Delft. ‘The one big advantage
of a battery is that it provides continuous power, allowing for uninterrupted
operation of a device. But a battery is hazardous, bulky and it has a chemical
impact on the environment. Without regular maintenance or replacement, it also
limits the useful lifetime of any wireless device to about a year, perhaps two
years.’ His words of concern are echoed by Josiah Hester, assistant professor

in the Computer Science department at Northwestern University, in Evanston, Illinois (USA).
‘A trillion battery-powered devices averages to 130 batteries for each person on earth. Do wereally want to spend a lot of time replacing them and building these giant warehouses full ofdead batteries? Rather than try and change people’s behaviour, we may be able to provide sometechnological solution to mitigate or delay the environmental impact of computing.’
Obviously, your internet-connected alarm clock or fridge can be plugged into a wall outlet.
But when you bury thousands of small sensors into concrete to monitor a skyscraper’s structural
integrity over its lifetime, or when you envision the future of preventive medicine to be poweredby deep-tissue micro-implants, these devices need to operate, maintenance-free, for decades.
According to Pawełczak ‘it is unrealistic to expect improvements in battery technology to solve
this. To allow near-permanent sensing at low cost and at a reduced ecological impact, we haveto rethink how we design these systems. We have to let go of the concept of continuous
operation. Batteries must be left behind.’

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Remember, remember, remem…
From left to right: Vito Kortbeek,
Jasper de Winkel, Przemysław
Pawełczak and Carlo Delle Donne.

Whereas classical programming and hardware architectures for wireless devices assume
a continuous power source to be present, a batteryless sensor harvests its energy fromthe environment – by using a solar cell, scavenging energy from radio waves or by converting
thermal or kinetic energy into electricity. ‘These are virtually unlimited energy sources,’ Pawełczak
says, ‘but next to providing only weak power they are unpredictable and can only power a device
intermittently.’ Removing the battery therefore only works in situations where you are lax about
the exact time something is supposed to happen, such as a temperature measurement or

About Przemysław

computing a moving average. ‘It also introduces a whole spectrum of new problems, threatening

Przemysław Pawełczak was born in Poland.

proper operation of these devices,’ Hester explains. ‘Buffered energy may be depleted up to

In 2009 he obtained his PhD at TU Delfta hundred times per second. Such power failures require a reboot, resetting computationalon ‘Opportunistic Spectrum Access’ andprogress and deleting any data stored in volatile memory.’ A new approach to computing was

subsequently joined research groups in Los

needed to ensure proper computational operation under these circumstances. It has led to

Angeles and Berlin. About five years ago he

the paradigm of (batteryless) intermittent computing.

‘Basically, grandma herself
should be able to build anInternet of Things device tomonitor her pills.’

changed from telecommunications to the field

Intermittent computingof batteryless intermittent computing. Now, as

In intermittent computing, sensing,an assistant professor in the Embedded andNetworked Systems Group at TU Delft, he mainlycomputation and communication tasks

works on the software-side of intermittent

proceed when enough energy has been

computing, sometimes building his own

harvested to turn on the processor.

hardware from existing components. He likes to

Program execution will continue until the

do long-distance runs, intermittently of course.

stored energy is exhausted again and thedevice abruptly fails. ‘The paradigm ofintermittent computing is to frequently

save the program state into non-volatile memory,’ Hester explains. ‘But the more often you dothat, the less time you have for local computations and the less memory you have available
to store local sensor data. Writing to memory also drains the device’s stored energy.’ Most
contributions in the field of batteryless intermittent computing are about how to implement thisstrategy on existing computer hardware. ‘It is about how to write the code in such a way that it
will sustain computation regardless of frequent power interruptions, while also introducing theminimum amount of overhead,’ Pawełczak says. Having met at multiple conferences, Pawełczak
and Hester discovered their shared interest in proving the feasibility of a sustainable Internet ofThings; energy-neutral, low maintenance and with a low ecological impact. They decided to join
forces rather than compete. Together, and with their group members, they have now addressed
two major challenges in intermittent computing – how to reliably keep track of time and how toease the burden of programming these devices.

The researchers integrated theirtimekeeping solution into a custombuild hardware and software platform,
called Botoks.

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It’s about time

‘The major advantages of a remanence

Timeouts and timestamps are the backbone oftimekeeper are that it can be miniaturised

any computing application, in particular thoseand that its components cost less thandesigned for sensing and communication.

a penny,’ Pawełczak says. ‘Combining various

Therefore, reliable timekeeping is one of theremanence timekeepers, we were able tocore challenges in intermittently operating

design a solution that allows batterylessbattery­less sensors. ‘Knowing how much time

timekeeping with millisecond resolution

has elapsed also allows a device to decide on

for power outages lasting up to seconds.

the validity of any stored data,’ Hester says.

It also has a very low start-up time of only

‘A device may experience a prolonged power

milliseconds and a low energy demand.’failure right after taking a measurement.

The researchers integrated their timekeeping

When it comes back online, should it transmit

solution into a custom-build hardware andthese stored data or first take a new andsoftware platform, called Botoks. Aside ofmore representative measurement?’ Existing

the new timekeeper, it consists of a sensor,

solutions for tracking time, such as ultra-low-

solar panel, micro controller, radio platform

power real-time clocks, have start-up times ofand an antenna. ‘We don’t want to just do

up to seconds and require a substantial energy

a simulation and write a scientific paper,’boost after each power outage. They are

Hester says. ‘We have to show that it actually

therefore unfit for intermittent computing.

works. We therefore benchmarked Botoks

The researchers instead focussed on thefor computational speed, energy efficiency

use of so-called remanence timekeepers

and memory overhead under various energy(see image on the previous page).

harvesting conditions.’

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Just an extra piece of code

to intermittent computing. ‘The research

At the moment, batteryless intermittent

community is starting to recognize this ascomputing is still a niche topic within the fielda very interesting and solvable problem, thatof computer science. ‘There may be aboutpromises to have a huge impact,’ Hester says.

ten groups involved worldwide, but these‘We see that in the increase in scientific publi­

are all based at preeminent universities,’

cations on this topic. With the community

Pawełczak says. The topic is, however, rapidly

convinced, funding agencies will follow.’ Forgaining traction. For the first time ever, onea sustainable Internet of Things to becomeof the major computer systems conferences

a reality, however, batteryless intermittent(ASPLOS) has featured a session dedicatedcomputing has to become much more widelyadopted by both consumers and businesses.

Remanence timekeepers‘It is about perception and people using
these devices,’ Hester emphasizes. ‘Basically,

A remanence timekeeper essentially consists of a

grandma herself should be able to build

capacitor and a resistor. A capacitor is a device that canan Internet of Things device to monitor her

store electrical charge, a resistor is a device through whichpills.’ The researchers took a large step inan electrical current can flow. You can think of them asthat direction by developing and releasing

a bucket and a faucet connected to the bottom of the

TICS (Time-sensitive Intermittent Computing

bucket. Using available electrical energy, the capacitor is

System). ‘There are millions of existing

charged (the bucket is filled). With more electrical charge

computer programs out there, designed forstored, the voltage across the capacitor increases (thecontinuously-powered systems,’ Pawełczak

water level rises). When power is lost, the capacitor will

explains. ‘To run these programs successfullydischarge through the resistor (water will flow through theon intermittent devices, under frequent power

faucet, emptying the bucket). The change in voltage acrossfailures, would normally require massive

the capacitor (change in water level) once power returns

re-engineering. TICS allows these old legacy

is a measure for the time elapsed between two reboots.

codes to run as is, handling such importantBy varying the size of the capacitor (bucket) and resistor

aspects as memory management, the passing(diameter of the faucet) it is possible to optimize thetiming characteristics of a remanence timekeeper.

of time and data-validity.’ TICS also brings batterylesscomputing right up to the doorstep of computer
hobbyists. ‘They can continue to use their classicalprogramming skills, including all advanced features ofthe programming language,’ Pawełczak continues. ‘They
just have to rely on an extra piece of code that they haveto upload to the system.’

Unlimited applications
Batteryless devices open up whole new application
domains, way beyond an Apple watch that you neverneed to plug in, should that have been the first thing tocome to your mind. Think of wildlife tracking, massivescale agriculture via augmented insects and satellites
the size of postage stamps that collect atmospheric
data and orbit for years. So, not even the sky is the limit.
And the impact of batteryless computing may go wellbeyond tiny devices. ‘From a scientific point of view, we
design things that are the ultimate of resilience,’ Hester
says. ‘What is harder than making a computer work while
experiencing a hundred power failures per second? Wetherefore expect developments in batteryless computing
to show up in other fields of computer science as well.
After all, people in large-scale computing, in spacesystems and security systems, are also continuously
wondering how to make their systems more robust to
failures.’ Although it is hard to predict its arrival, we canall look forward to a future with batteries not included.
‘But for now,’ Pawełczak says, ‘for our work to really
become generally known, we may have to prove thatbatteryless computing is not limited to tiny sensors forscientific use, and that it also works for larger devices
such as consumer electronics. We are working on that.’

About Josiah
Josiah Hester comes from an indigenous,
native Hawaiian background and grew up
caring about the environment. In 2017 heobtained his PhD on ‘Sophisticated BatterylessSensing’. He is currently an assistant professor
in the department of Computer Science,the department of Electrical and Computer
Engineering and the department of Preventive
Medicine, all at Northwestern University inEvanston, Illinois, USA. He works on both thesoftware and hardware side of intermittent
computing because ‘codesign allows you tomake something small, lightweight and perfectly
tuned to the problem you are trying to solve.’
His favourite areas of application are preventive
medicine and large-scale smart agriculture.

SCAN!

During ASPLOS, Jasper de Winkel (one of the members of the TU Delft team) gave a presentation
about reliable timekeeping for intermittent computing. ASPLOS is a multi-disciplinary conference
for research that spans the boundaries of hardware, computer architecture, compilers, languages,
operating systems, networking, and applications. ASPLOS provides a high quality forum for scientists
and engineers to present their latest research findings in these rapidly changing fields.

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11

Developing a digital twin
for the electricity grid
Text: Merijn van Nuland | Photography: Mark Prins

Imagine you have been working quietly for years in the confines of a large
academic institute, and, all of a sudden, dramatic changes turn your familiar
world on its head. The spotlights are pointing in your direction and suddenly
all eyes are on you. What would you do?
This is exactly what happened to Peter Palensky, professor at TU Delft.
His specialism – intelligent electricity grids – has suddenly become a hot
topic in recent years. The rapid transition to renewable energy has raised an

The rapid transition to renewable energy threatens to cause

important question: is our existing electricity grid capable of withstanding

major problems to the very expensive electricity grid in thesuch far-reaching changes? Palensky and his colleagues need to answer

Netherlands. In his quest for solutions, Professor Peter Palensky
is now working on a digital twin to make it possible to study thegrid effectively.

that key question to prevent the move towards increased sustainability fromfaltering.

Everyone an energy producer

This green revolution
brings somehuge problems ofadaptation with it.
Connecting a windfarm can completelychange the dynamics
of a country's
electricity grid.

For around fifty years, everything remained more or less the same. Everycountry had several large energy plants that delivered electricity on the gridfor millions of customers, in other words citizens and companies. But the
emergence of renewable energy has suddenly added countless new energy

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About PeterPeter Palensky (Austria, 1972) has been professorof Intelligent Electric Power Grids at TU Delft since‘We have a moral obligation towards the younger generation to combat
climate change. Technology is an important way of achieving that.’2014. Previous positions included principal scientist
in the Complex Energy Systems research group at
the Austrian Institute of Technology. He has also
held posts as assistant professor or researcher atthe universities in Pretoria, Vienna and Berkeley. He
is currently editor-in-chief of the IEEE Magazine on
Industrial Electronics.
Palensky is certainly not the type to shy away from achallenge like that. Quite the contrary. ‘As a scientist,
it’s actually quite a privilege to find yourself in thisposition,’ he says. ‘It’s as if we are at a turning point inhistory and have a real chance of changing the world
for the better. It’s an absolutely huge responsibility,
but one day we may be able to say to our children:
we did it.’

network. Before that, the existing High-Voltage Lab at‘hard facts’ from TU Delft will prove crucial because

TU Delft will need to be converted into an Electrical

it would otherwise take much longer to resolve these

Sustainable Power Lab, the ESP Lab for short. In it, it

kinds of complex infrastructural issues. Besides, thiswill be possible to combine crucial elements from theinvolves sensitive information that it is advisable notelectricity grid, such as high-voltage masts, wind andto obtain from distant countries: recent cyber attacks

solar energy, energy storage and distribution networks,

abroad have shown that the electricity grid is a popular

into one functioning whole.

arena in which to wage an electronic war.

Palensky’s first objective will be to investigate how

Palensky and his colleagues are currently working on athe existing Dutch electricity grid responds to stimuli

proposal for funding from the Dutch Research Councilor shocks, such as new wind farms or foreign cyber(NWO), to enable them to complete their digital twin.

attacks. But, in the near future, he also intends to do‘It would be a terrible waste if we can’t make progress

what scientists love best: innovate. ‘I’m interested innow. TU Delft is a world leader in this field and we see

finding out if we can develop an alternative electricity

on a daily basis how much Dutch grid operators cangrid that’s more adapted to the modern age. It’s very

benefit from our knowledge.’

unlikely to replace the existing grid any time soon,
but I think we have a lot to learn from this theoretical

So what is Palensky’s secret weapon? ‘My students.

exercise.’

They’re the ones who often have the smartest andproducers, because every wind turbine or solar panel

Digital twinis actually an energy plant in itself. All of a sudden,

Palensky hopes to answer these questions withthe citizens are no longer customers, but actually thethe help of a digital twin, a digital copy of the Dutch

Hard facts from TU Delft

suppliers! Very variable suppliers, as well, since windelectricity grid. On a digital copy, you can experiment

The digital twin will provide grid operators, such as

more, we have a moral obligation towards the younger

speeds and solar power tend to fluctuate.

and research to your heart’s content without the risk

TenneT, with a lot of information on how to make andgeneration to combat climate change. Technology isof breaking anything. ‘It’s actually a dream version of

keep their networks stable. Palensky believes that thean important way of achieving that.’‘This green revolution brings some huge problems of

the real grid,’ he says. He adds with a laugh: ‘Obviously,

adaptation with it,’ says Palensky. ‘For example, think

we’re not allowed to tinker with the real electricity grid,of the countries that have to connect large wind farms

so we have to do it this way.’most creative ideas. I also think it’s important to givethem access to the best machinery possible. What’s

to the existing electricity grid. Suddenly connecting alarge amount of new capacity can completely change

Palensky and his colleagues have actually borrowed

the dynamics of a country’s electricity grid, eventhe idea from large companies. Aircraft and car manu­

leading to a power failure in the worst case.’

facturers have long been using digital twins to test
their planes and vehicles. Examples include simulators

This means that research is required. A great deal ofthat use 3D images, sound and movement to replicate

research. Will the Dutch grid be capable of withstan-a real car ride or aircraft landing. Palensky’s digital gridding a new wind farm off the coast of Zandvoort?

is similar, but obviously without a driver’s seat and seat

How will we keep everything stable when, in the nearbelts.

future, millions of solar panels have been installed byindividual house owners? And how can we ensure thatOne small digital twin is already operational. The real-

everyone will be able to charge their electric vehicles intime digital simulator (RTDS), packed with software full

the future?

of mathematical calculations, can simulate a quarterof the Dutch grid. In the near future, this version is
set to be replaced by a digital copy of the whole74

The digital twin will provide grid
operators, such as TenneT, with a lotof information on how to make andkeep their networks stable. The ‘hardfacts’ from TU Delft will prove crucial.

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12
20

How smart sensors can prevent
epilepsy
Text: Koen Scheerders | Photography: Mark Prins

In Delft and Rotterdam, Wouter Serdijn and Christos Strydis arecollaborating on a network of sensors and stimulators for the
body. By picking up signals and sending the brain a rapid wakeup call, they hope to be able to predict and prevent epileptic fits.
‘If we can close the loop, we’ll have the technology ready within
three years.’

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Epilepsy is a collective name for disorders of the brain caused by a change in the brain cells’
electrical activity. These neurons suddenly become overactive, firing their electric signals
uncontrollably. This sometimes results in a ‘short-circuit’: seizures where a patient loses
consciousness or has involuntary muscular spasms. For the more than 200,000 Dutch people
with epilepsy, this can be very dangerous. But what exactly happens during an epileptic
seizure? What exactly do the overactive brain cells do? And how can we influence that process?
Wouter Serdijn, professor of Bioelectronics at TU Delft, is trying to answer these questions byresearching and designing technology for monitoring, diagnosing and treating epilepsy.

Get-together‘Do you know the band Rage against the Machine?’ asks Wouter. ‘I always compare epilepsy totheir song Killing in the name of. Epilepsy experts
say I’m mad for making the comparison, but that’s
what the signals remind me of. In the chorus,
everyone’s jumping all over the place.’ That’s what
happens with brain activity during a seizure. All
the neurons synchronize, reducing the exchange

About Wouter and Christos

of information to zero. The result is an epileptic fit.

‘It’s actually totally logical for neuroscientists andengineers to join forces,’ says Wouter Serdijn. He is

That kind of seizure can really affect patients’professor of Bioelectronics in TU Delft’s Faculty ofquality of life, says Wouter. ‘All of those 200,000

Electrical Engineering, Mathematics and Computer

Dutch people are prohibited from driving or using

Science. He has spent his academic career inheavy machinery.’ They also need to exercise

Delft: from his Master’s degree to his appointment

constant caution in their day-to-day lives: stress or

as professor. ‘I’m a Delft boy. In some ways that’s

flashes of light can trigger a seizure. In addition,

actually quite boring. But I just think TU Delft is an

drugs are not always successful in preventing

amazing place.’ Wouter is one of the few engineers

seizures. ‘In major seizures, the brain cells simply

with an innate interest in medical technology.

break down. They literally become exhausted andHe applies his expertise in bioelectronics to his work

die.’ Wouter is therefore applying a technologicalon such areas as pacemakers, hearing implants andperspective in his search for solutions that could

neurostimulators.

help the body prevent these ‘wayward gettogethers’ between brain cells.

‘You call it boring, but you have quite a few miles
on the clock,’ says Christos Strydis. He did his
Master’s degree in Computer Engineering in TU Delft
where he also completed a doctorate. His careerin neurosciences took off in Rotterdam, first as a
postdoc and now a tenured assistant professor with
the Neuroscience Department of the Erasmus MC.
Since then, he has worked as an assistant professor
in the Neuroscience Department at Erasmus MC in
Rotterdam. As an engineer there, he forms a bridge
between neuroscience and technology. Together with
Wouter, Christos was recently awarded a grant by
the Delft Health Initiative to develop the ECLEPSys
project as part of Convergence, the joint programme‘In the chorus, everyone’s jumping allover the place.’

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of TU Delft and Erasmus MC in Rotterdam.

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79‘In a fit, all the neurons start jumping at thesame time. In major seizures especially, theyliterally become exhausted.’

Wake-up callRocket science with patients

As professor of Bioelectronics, Wouter is

Christos Strydis is one of the researchers ofworking on technology that interacts with theErasmus MC who is bridging the gap between

electricity in the body, attempting to measure

the clinic and the technology. A computerand influence it. But, for epilepsy, that’s easierengineer with roots in Delft, he works as

said than done: just like with the crowd

an assistant professor in the Neuroscience

jumping up and down, you have little control

department. ‘I sometimes feel like a translator,’over it. The entire cerebral cortex – the area ofsays Christos. ‘In Rotterdam, there’s a lot of

the brain that receives, interprets and analyses

knowledge about brain function and how the

information – is involved in the process, says

different parts of the brain interconnect andWouter. ‘So, what you need is a wake-up callthe people in Delft have a lot of experience

for the whole cerebral cortex that can restore

in building technological solutions.’ Christos

normal communication without bringing it to a

has to speak both languages. ‘Some ofstandstill.’the bioelectronic solutions we devise for‘In Rotterdam, there’s a lot ofknowledge about brain function andhow the different parts of the brain
interconnect and the people in Delft
have a lot of experience in building
technological solutions.’

neurosciences are not rocket science, but
Together with the Erasmus MC in Rotterdam,others are. If we stayed in Delft, we engineers

he is conducting research on the role ofwould never be able to gain experience withthe cerebellum in conveying information.

patients or, we would never really understand‘The cerebellum regulates the body’s motor

the essential minutiae actual neuroscientists

movements and it branches into all parts offace.’

the brain. These connections can help us close

Sandboxthe loop: accurately detecting where and whenWith that in mind, Wouter and Christos are

ECLEPSys involves building a medical body area network (MBAN). This is aa seizure develops, making an intervention

setting up a platform to explore the medical

partly wireless network made up of wearable, injectable and implantable nodes,that can reach all parts of the brain and thenissues surrounding epilepsy from an engi-

each with its own task: sensors, stimulators and a computer that coordinates

measuring the effect of that intervention.’

neering perspective. They have received athe signals with each other. An MBAN is more effective than existing technology

grant from the Delft Health Initiative for their

because it is capable of measuring on or next to the body and intervening in realwork. Their project ECLEPSys – Ensemble,

time, tailored to each patient's particular needs. ECLEPSys can therefore make

Closed-Loop, Epilepsy-Prevention System –a difference in epilepsy in particular, but Christos has even bigger ideas. ‘The

consists of a prototype of a sensor network

MBAN could also be used to treat other disorders: heart arrhythmia, Parkinson’s,

made up of implantable and wearable sensors

migraine or tinnitus. We aim to demonstrate that it is possible to help patientsand stimulators. The first group measures

by applying machine learning and smart algorithms to biosignals.’ ECLEPSys

signals from the brain and the second links a

can be compared to a sandbox, where diverse ideas and novel technologies

signal back into the body. The idea is that thecan be tested. ‘Examples could include new sensors, new forms of stimulation

signal should stimulate the brain cells in suchand ways of analysing personal data. But the project also encompasses data

a way that they revert back to normal.

security, which has already become a nemesis in the modern digital world.’

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By measuring brainwaves andstimulating the cerebellum, Wouterand Christos were able to suppress
an epileptic fit elsewhere in the brain.

‘There is significant variability
between patients. That calls
for a different approach.’But before epileptic patients can start driving again, there’s still a lot of work

SCAN!

to be done. The energy management of the sensors and stimulators requires
improvement, for example. The technique that Wouter and Christos are using
has still not been cleared for use on humans. ‘Our system is still not a network.
We’re working on other ways of getting signals into the brain. Instead of EEGs,
we’re working on different types of feedback. We know that the body sends
signals before a fit starts: sweating, dilated pupils or an increased heartbeat.
We need to learn to use that information.’Translating‘If we engineers all
stayed in Delft, we
would never haveexperience withpatients.’

For epilepsy patients, it is hoped that ECLEPSys will bring about

Before Wouter and Christos can use the system on patients, they aim to makea new treatment method, combined with drugs. ‘I expect thatit as efficient as possible first. The collaboration between Rotterdam and Delft is

this will enable us to suppress or control epilepsy,’ says Wouter.

essential in this: the realism of the medical experts in Rotterdam keeps the Delft‘The great thing about this type of neurostimulation is that you

engineers and their get-things-done mentality in check. ‘We would never havejust switch it on and it works immediately. And vice-versa: you

made such progress without our contact with Erasmus,’ says Wouter. ‘Engineers

stop if you no longer want it. That makes treatment personal

believe in the power of repetition. If we make something twice the same way,

and targeted. Drugs can never be so fast: they don’t know

it also needs to work the same way. That principle does not work on patients.

where in the body they’re supposed to go.’There is significant variability between patients, and even in the same patientWork to be done82

Wouter Serdijn was a guest lecturer
on the Dutch show Universiteit van
Nederland. Scan the QR-code to hear
Wouter explain his research(in Dutch).

at different times. That calls for a different approach.’

But that is still some way off, says Wouter. ‘We already haveBesides that, it’s not only about the technology, adds Christos. ‘Before rollinga system that can detect and suppress epileptic fits but it

this out to more people, you have to discuss such issues as ethics and qua-

only works with mice at the moment. Their cerebellum islity-of-life. You cannot measure brain activity everywhere in the body. Do you

very similar to that of humans.’ By measuring brainwaves

really want to burden a patient with all kinds of sensors on his head?’ Despiteand stimulating the cerebellum, Wouter and Christos were

this, Wouter thinks that the technology behind ECLEPSys can be translated forable to suppress an epileptic fit elsewhere in the brain. That

human use within the foreseeable future. ‘You cannot apply substandard work

demonstrates that the principle works, says Wouter. ‘We wereon people. But I’m still optimistic. If you can predict epileptic fits with the rightable to detect that a fit was coming within 0.4 seconds andsignals, we can close the loop. Then we’ll have the technology up-and-runningstop it.’

within three years.’

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Modelling a flexible
electricity system

13

Text: Dave Boomkens | Photography: Mark Prins

In most cases, electricity is transported from point A (where it is generated)to point B (where it is used). Huge quantities of electricity are sent over thehigh-voltage national electricity network, while the electricity that comes outof the plug socket at home is part of the low-voltage distribution network.
Using numerical analysis, TU Delft PhD student Marieke Kootte is developinga model to link these two networks. ‘Because,’ Kootte explains, ‘the energy
transition, which is having a huge impact on our national grid, makes it
increasingly important to also focus on the low-voltage distribution networks
in more detail.’

It is hard to imagine a landscape with no power lines, buthave you ever thought about the route that the electricity
takes through the thick cables before eventually reaching your
iPhone? Marieke Kootte didn’t really think about it either, until‘There is still muchto be done when it
comes to coupling
low- and highvoltage electricity
networks. That’s
how the wholething started.’a call was released by the Dutch Research Council (NWO)
for research to give the energy transition a push in the right
direction using computational intelligence (the learning abilityof computers). ‘This closely matched the expertise available
in Professor Kees Vuik’s team, which is high performance
calculations in large electricity networks,’ explains Kootte.
‘I decided to take a closer look at the subject, and found that
there is still much to be done when it comes to coupling lowand high-voltage electricity networks. That’s how the wholething started.’

Generated energy
Marieke is now a PhD student and the NWO call forms thebasis of her research. In this research, she also makes useof knowledge gained in earlier projects. ‘I once took part in a
project to find out how quickly drug waste enters the seweragesystem. I simulated how the mix of chemicals spreads in 2D,
and did the calculations on my laptop. But to do this for thewhole of the groundwater system in the Netherlands, you
would really need to use numerical analysis. Using computer

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About Marieke
TU Delft PhD student Marieke Kootte is developinga model to link two networks. ‘Because,’ Kootte
explains, ‘the energy transition, which is having
a huge impact on our national grid, makes it
increasingly important to also focus on the lowvoltage distribution networks in more detail.’models that you develop using numericalown way, and they are hesitant to share thisanalysis, you can map this kind of thing really‘sensitive’ information. When I started myquickly, saving a lot of time and computing

research, this was a huge problem. Luckily,

power. For this study, I am applying the same

now that the energy transition is taking off,

trick to the electricity grid in the Netherlands:

more information is being shared between thea network that is made up of thousands ofoperators.’

cables and connections. Each cable has acertain resistance, and a connection is a point

Flexibility

at which energy is either generated or used,

In Delft, Kootte focuses mainly on analysing

such as a house, or a whole neighbour­hood.

the electricity network, but 70 kilometres

Once we have mapped the details, we can run

away – at Sympower, an Amsterdam start-up

a powerflow simulation to obtain a voltage– she is working on another part of her PhD

profile. This gives an idea of what is happening

research. Kootte: ‘If there are fluctuations inin the grid. It provides useful information for thethe supply and demand of electricity in thegrid operators, especially if they want to build

network, gas- or coal-fired power plants area new network or connect a renewable energy

usually used to make up the difference. That issource to the grid.’

often expensive, and it’s not very sustainable.

Sharing is caring

If there is a shortage or surplus of electricity inthe network, Sympower switches appliances

The electricity network is so big that simple

that are not directly needed on or off, or higher

models (which describe a few connections)or lower. They therefore play with the demand

are often not enough, and can give a distortedside of the electricity network. For example,

picture of reality. So, for modelling at suchlots of cold storages in the Netherlands area large scale, numerical analysis really is theset at 7°C. If there is a shortage of electricity

best option. ‘But even so,’ says Kootte, ‘there

somewhere, then Sympower could switch off

are still some complicating factors. One

those cold storages (in participating super­

example: the generated energy is transported

markets) for a few seconds. As a result, theover long distances through the nationaltemperature may increase to 8°C, for example.

grid and transformed to a lower voltage

The demand for electricity decreases locally,at certain points in the network for use in

and balance is restored to the network.

homes and industry. What makes things

Controlling the storages remotely in this way

difficult, is that each of these networks hasmeans that no polluting resources need to be

its own grid operator. These grid operators

used to restore the balance.’

each map the distribution networks in their

86

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87

‘There are two ways to do it. One way is

A huge laboratory is currently being built at

to assume that grid operators share all

TU Delft – the ESP Lab – to investigate thetheir data with one another. The other is tobest way to transport electricity produced byassume that grid operators keep all theirwind turbines and solar panels to the pluginformation to themselves, except when it

sockets in our homes. One of the people

concerns a common connection. In the caseinvolved in the ESP Lab is Peter Palensky.

of the second scenario, you can use a simple

He is developing a digital twin for the elec-

model for the calculations.’ However, notes

tricity network, to answer the question how

Kootte, at the same time more and more

to keep everything stable when, in the nearenergy is being consumed and more is being

future, millions of solar panels are installed byproduced locally. This increases the level ofindividual home­owners. ‘Peter is specialised indetail required, and therefore the size of theintelligent electricity networks,’ says Marieke.

models needed. Furthermore, energy from

‘It therefore makes sense for us to meet up

sun and wind is inherently unpredictable. ‘If

now and again to discuss the issue. He knows

you then link the high-voltage network to theeverything about the network, and we do the

low-voltage network, the model becomessuperfast analyses.’pretty complex, with more than a million
connections. The best thing then is to use a

Well-known pass

GPU – a special processor that is designed to

It is not just in her work that Marieke tries

process graphical data. A GPU can process

to make sure that we use the earth in a way

multiple tasks simultaneously, so that thethat ensures its continued use for future

analysis can be done more quickly. A GPU

generations. One of the things that she does,

is used differently from a normal computerin addition to her PhD, is make sustainable(CPU), and that is where we – mathematicians

clothing. ‘On Tuesday evenings, I follow– come into the picture. What my goal is? To

a seamstress course,’ she says with a grin on

Finnish greenhouse horticulturists

To the emergency room

apply GPU processing to increase the speed

her face. ‘That means, making new clothes

A flexible electricity system that matches

Another optimisation issue that Kootte hasof the software that grid operators use, so

and altering existing clothes. I love doing it,

demand to supply could make an importantworked on relates to electric cars. What isthat they can respond more effectively andtaking along my own fabrics, learning thecontribution to the energy transition. Testing

the most efficient way to charge, let’s say,so that electricity is always available, with aold-fashioned techniques… I am also a pretty

such a system does not stop at the Dutcha group of 8,000 cars? ‘You can predict whensimple push of a button, even in this rapidly-

fanatical cyclist. I take part in the Amstel Goldborder. For her research, Kootte ‘controlled’

each driver leaves or returns home, but you

developing world.’

Race every year, and I have cycled the Liège-

the lamps in greenhouses for growers in

can also calculate how many cars leave andFinland. ‘Plants need water, food, humidity

return each hour. If the electricity network

Huge laboratory

and a minimum temperature, but of course

is experiencing a peak load, you let lessMarieke is not the only one working on thisI wanted to cycle the Stelvio pass, a well-known

also light to grow. It does not really matter at

electricity out of the charging point so that

subject at the Faculty of Electrical Engineering,climb in the Italian Alps.'

what time the plants absorb this light during

the car charges more slowly. And therefore

Mathematics and Computer Science (EEMCS).

the day, as long as they get a certain minimum

prevent overload on the grid. Of course, youamount of light. That means, enough light forneed to build in a safety margin so that you

photosynthesis to take place. The plants dodon’t have a situation in which you need to

however need a certain amount of light eachdrive to the emergency room at 2 o’ clock inhour to stop them from ‘falling asleep’. So

the morning only to discover that the battery’s

what we did was to predict the daily energy

not even half full. Nobody wants that.’

price fluctuations as precisely as possible.
Then, during the most expensive hours, we let

Back to the future

the plants sleep, and turned up the lamps to

Back to Delft, where Marieke is connecting

maximum during the cheapest hours. No morehigh-voltage and low-voltage distribution

than a simple optimisation issue.’networks. How exactly does she do that?

88

Bastogne-Liège race several times, the final
race of the spring classics. This summer,

A flexible electricity system thatmatches demand to supply could
make an important contribution to
the energy transition.

2020 | EEMCS NODES VOLUME II

89

14

New Electrical Sustainable
Powerlab smooths theway for energy transition
Text: Robert Visscher | Photography: Mark Prins | Infographic: Dirma Janse‘A power outage can have various causes, from a faulty
generator to a lightning strike and from broken cables
to an imbalance in power production.’

In a large hall, exploring the most effective way of getting electricity from wind turbines and solar
panels across the country to the wall socket in your home. This will be the mission of the new

A new laboratory, the only one of its kind in the world, is being
built in Delft. The Electrical Sustainable Powerlab will bringwill be operational in the beginning of 2021.

together under one roof scientists researching the generation,

According to TU Delft Professor of Photovoltaic Materials and Devices Miro Zeman, there istransfer, distribution and use of electricity by households anda real need for this new Electrical Sustainable Powerlab (ESP Lab). ‘The electricity system ascompanies. The aim is to ensure a smooth transition to moresustainable energy.

90laboratory in the Faculty of Electrical Engineering, Mathematics and Computer Science, which

we now know it is set to change completely,’ he says. Currently, most electricity is generated
centrally at coal-, nuclear- and gas-powered plants. They provide a stable supply of energy tothe electricity grid.

2020 | EEMCS NODES VOLUME II

91

ACTIVITIES ESP LAB
1O2

TU Delft program for developing
an electrochemical-based
technology for the conversion ofsustainable electricity into fuels.

H2

2
3

1
2

E-REFINERYNEIGHBOURHOOD
TU Delft program for developing
BATTERYanelectrochemical-based

E-REFINERY
O2

H2

4

MICROGRID
A microgrid is a localized groupof distributed electricity sources and loads that can operateautonomously or connected to
the general grid.

7

HOUSE OFTHE FUTURE
House of the future isequipped with an own PV
electricity generation,
storage and intelligent
control system.

10

SOLAR ENERGY
The renewable energy sourcewith the highest energy
potential. Solar energy can beconverted to heat using solar
collectors or directly toelectricity using solar cells.

13

DIGITALCOMMUNICATIONIn the future, more use will bemade of smart devices in thehome. They will 'talk' more toeach other for an optimal easeof use.

TU Delft Electrical
Sustainable Power Lab

ACTIVITIES ESP LAB

NEIGHBOURHOODCONTROL ROOMBATTERY
THE FUTURE
AOF
neighbourhood
battery

An increased
complexity
andenables
to storeselffast phenomenain the bygrida
generatedclean energy
require newfor
monitoring
andcommunity
use at a later
control principles
appropriate
time. facilitated bydigital technologies.

A neighbourhood
battery oftechnology
for the conversion
enables to store
self- into fuels.
sustainable
electricity
generated clean energy by acommunity for use at a later
appropriate time.

5
6

4
5

MICROGRIDELECTRIC CARSVEHICLE TO
Anelectric car is a car with an
GRID

ELECTRIC CARS

A microgrid is a localized group
electric carelectricity
is a car with
anofAndistributed
sourcelectric
motor
poweredbyesand loads
that
can operate
electricity fromoraconnectedbattery or toaautonomously
fuelgeneralcell. grid.
theelectric motor powered by
Vehicle-to-griddescribes
electricity
from a(V2G)
batteryor aa system
fuelcell. in which electricity canbe exchanged between the gridand a battery of a vehicle.

7
8

8
9

DOMOTICSHOME BATTERY

HOUSE
OF
DOMOTICSTHE FUTURE

A home automation system that
Home battery
is intendedfor
controls
householdappliances,home energy
storage,storeslighting,
climate,entertainment
excesselectricity
from
a
home
systems. When connected with the
PV system
to beInternet,they
areuseda partforof theload-demand
management
Internetof Things.
and off-grid use.

A home automation system that
House of the future iscontrols household appliances,equipped with an own PV
lighting, climate, entertainment
electricity generation,systems. When connected with thestorage and intelligent
Internet, they are a part of thecontrol system.
Internet of Things.

11
12

10
11

SOLAR ENERGYHIGH VOLTAGE
The renewable energy source
COMPONENTS
with the highest energy

HIGH VOLTAGE
WIND ENERGYCOMPONENTS
A renewablethat
energyofComponents
aresource
used forenergyof airtransmission
flow that canofbe
highvoltageconverted into electricity using
electricity.
wind turbines.

Components
are usedforpotential.
Solarthatenergycan behigh voltage
transmissionofconvertedto heatusing solar
electricity.or directly tocollectors
electricity using solar cells.

3

CONTROL ROOM
OF THE FUTURE

An increased complexity andfast phenomena in the grid
require new monitoring andcontrol principles facilitated bydigital technologies.

6

VEHICLE TO
GRID

Vehicle-to-grid (V2G) describesa system in which electricity canbe exchanged between the gridand a battery of a vehicle.

ENERGY TRANSITION,
HOW DOES IT WORK?

F

FOSSIL ENERGY TOO
1 FROMSUSTAINABLE ENERGY

11

In the Netherlands we are
currently using an energy system
based on fossil fuels. This ischanging to a system based
ed onrenewable energy sourcess such as
wind- and solar energy.

Variable and intterrmittentrenergy supply
If the sun doesn't shhine orhclouds pass by,b , no electricitylwill be ggeneerated byy solarpapanpanels.

39Home battery is intended forhome energy storage, stores
excess electricity from a home
PV system to be used forload-demand management
and off-grid use.

12

WIND ENERGY
A renewable energy source ofenergy of air flow that can beconverted into electricity using
wind turbines.

14
15

DIGITALURBAN ENERGYCOMMUNICATIONURBAN ENERGYPV TECHNOLOGYTU Delft program for delivering
PV technology
and
optimizing converts
the use ofsunlight
directly intoenergy
electricity
andissustainable
in thebuilt
expected to be a major supplierenvironment.
of useful energy in the built
environment.

Delftprogram
InTUthefuture,moreforusedelivering
will beand optimizing
the useinofthe
madeof smart devices
sustainableenergythe built
home.
They will'talk'inmore
toenvironment.
eachother for an optimal easeof use.

15

PV TECHNOLOGY
PV technology converts sunlight
directly into electricity and is
expected to be a major supplierof useful energy in the built
environment.

This infographic is made by Studio Dirma Janse

15

YOU KNOW, IT'S NOTT JUST
2 BUT,
LIKE THAT...

13

1

A electrical energy system
m based on
renewable energy sourcess is
confronted with many challenges,
allenges,such as weather dependent
nt
variable energy supply andddisturbances in the grid due
ue topower-electronics components.
nents.

O2

10
7
H2

14

9

4
2

Active cooperation
with external parties,
such as TenneT.

8

3 THAT’S WHY: ESP LAB

System integration
Integration of newelectricity generating
technologies and new gridcomponents ( ) into theexisting system.

ESP Lab is a unique facilityy whichenables to work on solutions
ons forthese challenges; secure power
quality and stability of thee grid. The
ESP Lab helps to acceleratee theenergy transition.

Autonomous energy cell
(Basic unit of a microgrid)
becomes an active player inelectricity generation andtrade.

6dc

ac

Disturbances are caused by thee
implementation of new gridcomponents suchh as powerelectronics that introduce fasttransient phenomena into thegrid.

Working together on a sustainable
and intelligent electrical energy
system of the future.

Main challenge of thesustainable energy system
Main solution of thesustainable energy system
1

Activities ESP Lab

electricity more unpredictable, so we need to

We are already seeing increasing numbers

use more measurement and control techno-of sustainable generators of electricity, suchlogy. Ensuring everything runs smoothly is

as wind turbines and solar panels. According

becoming a more complex process. That’s why

to Zeman, that will only increase in the years

we’re developing new methods to gain greaterahead. ‘People with solar panels can supply

control of electricity generation and consump-

power back to the grid. This means that powertion. It involves collecting a great deal of data.

is being generated not only centrally, but also

We use the term digital energy to describe thisat local level. It’s not only controlled by big

new approach.’

ACTIVITIESElectrical Sustainable
Power (ESP)ESPLab LABDelft University of Technology is working on one of the major societal issues of our time; the transition

companies, but by ordinary people like you andme. This two-way traffic is an important factor

This change will come about in the comingthat we need to take into account.’

years. Currently, research work on the energy
transition is done in separate labs in the

For the electricity grid of the future, the fact

department. For example, work on transportthat the supply from sustainable generation

over long distances takes place in a High-fluctuates also matters a lot. If it’s very windy

Voltage Hall and, in another lab, scientists

or there’s a lot of sunshine, more energy will

are testing components as converters for the

be available. ‘This has made the supply oftransport of electricity.

92

12

D

5

13
14

Research including the entire
electrical energy chain(electricity generation,transmission, distribution andconsumption) under one roof.

HOME BATTERYThis infographic is made by Studio Dirma Janse

Digital Energy

First laboratory in the world enabling researchand education in system integration of newcomponents and electricity-generating
technologies into the existing electrical grid forthe acceleration of energy transition.

pgyWhen no wind is blowing, no electricity
will be generated by wind turbbines.

Digitalization
With the help of digital technologies, thecomplex electricity grid is accurately
monitored, measured data arecommunicated and processed, resulting ina better control of the grid performance

towards sustainable energy. With its MSc and PhD
educational programmes TU Delft is preparing
young
3
2

1

O2

engineers both nationally and internationally to
become future energy leaders in realising thisCONTROL
far-reaching
E-REFINERYNEIGHBOURHOODROOMBATTERY
OF THE FUTURE
TU
Delft program
developingchangein theforenergy
supply and market. Industry and academic experts are working togetheroninnovations
An increased complexity andH2

A neighbourhood battery
an electrochemical-based
fast phenomenain the gridenables to store
selftechnology
for the conversionofthat contributeto a higher
efficiency for the electricity
generationfrom renewable energy sources,
electricity
require new monitoring andgenerated clean energy by asustainable electricity into fuels.
control
principles facilitated bycommunity
for compromising
use at a latertransmission & distribution and system services
without
the reliability of energy
supply.
digital technologies.
appropriate time.

In order to tackle the challenges of energy transition, multidisciplinary research programs based on system
54integration are required. The Electrical Sustainable
Power Lab will be a unique location where6these research

MICROGRID
programs will be executed.

A microgrid is a localized groupof distributed electricity sources and loads that can operateautonomously or connected to
the general grid.
2020 | EEMCS NODES VOLUME II

ELECTRIC CARS

An electric car is a car with anelectric motor powered byelectricity from a battery or afuel cell.

VEHICLE TO
GRID

Vehicle-to-grid (V2G) describesa system in which electricity canbe exchanged between the gridand a battery of a vehicle.
93About Radek

He is also keen to emphasise thetransmit but to distribute energy under‘Over the years, I’ve worked atimportant role set aside for the businessdirect current. The energy distribution

electricity companies and seen a lot

community. The scientists aim toat medium voltage direct current levelsof laboratories. The new Electricaldevelop new solutions in the lab thatat large scale has to be done in a safe,

Sustainable Powerlab will take uniquewill go on to be used by real companies.

efficient and reliable way,’ says TU Delft

position among other laboratories due‘Businesses will also need to see thescientist Armando Rodrigo Mor. He

to integral research approach covering

benefits of the solutions we devise. We

specialises in components that work at

the whole energy chain. That’s why I call

can come up with the most ingenious

high voltage.

it the laboratory of the future,’ says thedevices, but if they’re not used, nobody

In the near future, Rodrigo Mor expects

current manager of the High-Voltage

gains anything. We want to develop

to see two electric sockets in the home:

Hall, Radek Heller. He will also be thethings that really benefit people and help

one for direct and one for alternating

manager of the new ESP Lab.

society to progress. This new lab will

current. But that is still some way

certainly contribute to that.’off. The reliability of transporting

Heller is most enthusiastic about thehigh-voltage direct current over longsharing of ideas between the different

About Armando

researchers. Several research groups

In the coming years, new, large wind“The new lab will prove particularly

will soon be working in the same lab. ‘At

farms will be developed off the coast ofsuitable for that because we’ll be able tothe moment, there are lots of scientists

the Netherlands. They will produce direct

see what works most effectively for theworking on different pieces of thecurrent, but the electricity grid uses al-whole system”, he says.

puzzle, but we’ll soon all be solving theternating current and that means losses

whole puzzle together. I’m also looking

over long distances. Interestingly, mostThe lab will be operational in theforward to the mutual conversations

household devices use direct current,

beginning of 2021.

between the researchers in the lab.

including TVs, tablets and smartpho-

People from different departments will

nes. ‘We’ll soon be using the new lab tosoon be able to chat there.’

explore whether it´s possible not only to‘We'll now bebringing all of thisresearch together inthe ESP Lab.’

Radek Heller, Miro Zeman
and Armando Rodrigo Mor.

distances still needs to be improved.

From generation to the wall socket

Researchers will soon be able to investigate which cables are‘We’ll now be bringing all of this research together in themost effective, from generation through to the wall socket.

ESP Lab,’ says Zeman. ‘This will involve looking at the whole

Or to see what the effect is of converters that convert direct

system. Imagine we’re devising a new piece of equipment, suchcurrent from wind turbines and solar panels into the alternating

as a transformer or converter. The new laboratory will makecurrent on the electricity grid. ‘Other examples could include

it possible to test how everything connected to the electricity

a type of converter that enables energy from your solar panels

grid will react to it. In order to check that no faults develop andto be stored directly in the battery of your electric car. And if

to see if it works the way we think it does. In other words, we’ll

there is not enough electricity in the evenings, you can use

be testing the whole system rather than just the performancethe same energy again to keep the lights on. There’s so muchof the individual components. This is why the Electricalresearch to be done on everything from generation through to

Sustainable Powerlab will be essential in smoothing the way

the user and we can do all of that in the new lab.’‘We’ll be testing
the whole systemrather than justthe performanceof the individualcomponents.’

for the energy transition.’

94

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‘The apparent random motion of pollen inwater is a good way to model noise in, forexample, the realm of economics.’

Understanding noise –from quantum fluctuations
to climate models

15

Text: Merel Engelsman | Photography: Mark Prins

Noise adds arbitrary fluctuations to both physical and economical
processes. As a consequence, there are many abrupt variations insignals and measured values that should be either constant or varying
only relatively slowly. Although noise itself is unpredictable, its
influence can certainly be modelled. Using the correct mathematicalinsights, these models can then be solved.

962020 | EEMCS NODES VOLUME II

97

SCAN!

‘The more we know about the smoothness of afunction, the more efficient we can approximate
it with numerical methods.’

Inaugural speech.

Noise at any scalea model may more closely conform to reality.

About MarkAs professor in the Analysis group at theIt also allows us to make statements as toMark Veraar is professor in the Analysis

Delft Institute for Applied Mathematics

the likelihood of such unwanted behaviour,’Group at the Delft Institute for Applied(DIAM), Mark Veraar has a wide range of

Veraar explains. ‘It is for this reason that I also

Mathematics. In 2017, Mark Veraar wasmathematical interests. Noise has been one

investigate the long-term behaviour of model

voted best teacher of the department ofof these interests ever since he was a PhD

solutions. Will an equilibrium be reached, andmathematics as well as of the entire EEMCS

student. ‘Noise is everywhere, at every scaleat what timescale?’

Faculty. He has been the runner-up threeof observation,’ he says. ‘From quantum
fluctuations at the level of elementary

Hopping pollen

particles, through random motion of dust

‘I use the mathematics of the so-called

particles in a gas or a liquid, to turbulence inBrownian motion to model noise in problems

the atmosphere and in climate models. Noisein the realms of physics and economics,’

is not only a physical phenomenon, it is also

Veraar says. The Brownian motion is thea characteristic of economic processes suchphenomenon that small particles, such as

as a sudden rise in the financial markets

pollen, display a seemingly arbitrary patternor the fluctuations in the price of shares.

of motion when immersed in water. Their

Rounding errors in a computer are yet anothererratic bouncing around is a consequence ofkind of noise.’ It is fair to say that our world

many random collisions with the even smaller

is a noisy place. More importantly, noise canwater molecules. The mathematics of thehave a decisive influence within the models

Brownian motion is over a century old, butthat engineers and other scientists use to

new features continue to be discovered. ‘When

make predictions about this world. The few

modelled as such, noise is unpredictable andmeters rise in sea level as predicted by climate

it will have a uniform intensity,’ Veraar says. Inmodels will most likely be the consequencea climate model, for example, this means thatof (modelled) human activity. But it could,

the impact of noise does not depend on where

in a manner of speaking, also be due to a

you look (the location) or when you lookseemingly harmless rounding error running(at what modelled time).

times.

out of control. ‘By specifically modelling noise,98

2020 | EEMCS NODES VOLUME II

99

Hard and soft techniques

an indication of how efficiently you can makeMathematicians like their models to be as

statements about a certain mathematicalclose to reality as possible, making noise ansituation. It is often relatively easy to prove

important ingredient. Such models are often

the existence of an optimum – a best possible

based on so-called differential equations

outcome – using soft mathematics. Defining(see frame). Not the easiest subject matter

an efficient algorithm to find that optimal

to wrap your head around, but as a former

solution can, however, be very difficult. But

best teacher of the Faculty of EEMCS Veraar

sometimes it is much more difficult to use soft

knows how to explain patiently and clearly.

mathematics. In my research I try to stick with

‘A model and its solution are two entirely

soft techniques, resorting to hard techniques

different things,’ he says. ‘It may be clear for

only when absolutely necessary.’ At suchan aircraft engineer that, when put in a winda moment, a computer may be required

Partial Differential Equations (PDE)
A relatively simple example of a PDE is the heat equation. It describes
the temperature distribution in a one-dimensional rod and how itchanges over time.
∂u(x,t)∂t

the numbers 1 to 100.

∂X2

time t. On the left of the equal sign you find the time derivative of u(x,t) –how quickly does the temperature at point x vary, in degrees per second.
On the right side you find the second derivative to the location – if I
look in the neighbourhood of x, do I observe an increase or a decreasein the speed with which the temperature changes. The heat equation isan exact description of the solution. It does, however, not give you theapproximation or a technicalA soft mathematical approach is much more efficient for adding∂2u(x,t)

The function u(x,t) describes the temperature for each coordinate x at

to perform a numerical

Hard and soft mathematics=k.

function u(x,t), and thereby the solution.

estimation.

A smooth solution
Thanks to the ever-increasing
computational power, themathematical models usedsmoothness of a solution. In mathematical

moments while for an aircraft engineer it may

by engineers and otherterminology this is called ‘regularity’ and it ismean that, next time, he may not have to build

scien­tists have become more

an indication for how often one can determinea scale model and put it in a wind tunnel.

and more realistic. ‘It may,the derivative of a function (a measure for how

Nevertheless, Veraar is already considering

however, still be the case thatquickly a function value varies, see frame),a further expansion of his knowledge. His

tunnel, his experimental wing design results ina prohibitively large number of calculations isand whether or not these derivatives are ‘well-

one-and-a-half-year-old daughter adds somea certain airflow. Using a mathematical model,

required to approximate the solution of

behaved’. ‘It is especially this smoothness ofvery positive noise to his plans, but he may

however, it isn’t always possible to makea model,’ Veraar says. ‘The better under­a solution that allows the implementation ofuse the first semester of the upcoming

any statements about that airflow.’ Veraar isstanding we have of the properties of aefficient numerical approximations,’ Veraar

academic year for an international researchinterested in a fundamental understanding

solution, the more efficient an algorithm

explains.

sabbatical. ‘I don’t yet know at what universityof the underlying equations, including noise.

we can implement, thereby staying within

In his research, he applies both soft and hard

computational limits.’ To attain such

Deep connections

mathematics (see frame). ‘Soft and hard has

understanding, Veraar enthusiastically

His current research interests are at the

research and mine, so that we can understandno relationship to the mathematics being

explores the depths of mathematics. One of

cutting edge of three mathematical researcheach other. On the other hand, their interests

simple or difficult,’ he explains. ‘Rather, it is

the aspects he delves into is the so-called

areas (functional analysis, harmonic analysis

should also be sufficiently dissimilar to allow

and probability theory) and have been quite

me to write an interesting follow-up projecta treasure trove. ‘At a very fundamental

proposal to my currently ongoing VIDI-grant.’level I have found unexpected connections

Wherever he may end up, noise will still be on

between these research areas,’ he says. For

his mind.

I wish to broaden my perspective. There has
to be sufficient overlap between their ongoinga mathematician these are satisfying eureka-‘Noise can have a decisive influenceon the predictive power of models’‘It may be clear for an aircraft engineer that, when
put in a wind tunnel, his experimental wing design
results in a certain airflow. Using a mathematicalmodel, however, it isn’t always possible to make any
statements about that airflow.’100

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Using mathematics to explain
why the River Ems is silting up

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Text: Robert Visscher | Photography: Mark Prins and Herman Verheij

Why are the River Ems and the Dollard inlet so turbid that theybarely harbour any life? Mathematician Henk Schuttelaars is working
on new models to improve our understanding of this puzzling riverand find solutions to the problems involved.
The River Ems and the Dollard inlet are located in the border area of northern
Germany and the province of Groningen in the Netherlands. The water there has
almost completely clouded up to the extent that it resembles liquid mud. Why isthat?
It’s caused by silt, a muddy substance that consists of clay particles and dead organisms. The
amount of silt has been increasing over the past decades and parts of the river are basically now
just liquid mud. This impedes the growth of algae, that are at the base of the food chain. Algae
are the food of shrimps and shellfish, which in turn are eaten by birds. This has led to severe
ecological degradation of the area and there is now almost no life left in the water.

But how did all that silt get there?

‘I work on newmathematicalmodels to better
understand theenigmatic riverand find solutions.’

We’re not exactly sure of the answer yet, which is why we are currently
researching this. What we do know, is that much has changed over the past
decades. For example, the Ems has been dredged to make it considerably
deeper, for instance to cater for the increasingly larger cruise ships being built
at the Papenburg shipyard in Germany. But land reclamation around the Dollard
inlet has probably played a role too, because this has reduced the size of theestuary. We also want to know more about the origin of the silt and where it
ends up. Before we can arrive at solutions to reduce the amount of silt andmake the water clearer again, we first need to understand which processes
affect this ecosystem. Otherwise there is no point changing anything; you
might even end up making things worse.

How are you conducting your research?
We’re studying various factors that all influence the transporting of silt. One of these is the
distribution of sediments throughout the water column, i.e. from the surface of the water tothe bottom of the river. We also want to find out where the silt is entering the water and we are
examining what happens under hyper-turbid conditions, which occur when a large amount of
sediment collects in one place in the water. This influences the flow of the water and so changes
the distribution of the silt. In short, we’re studying a whole lot of things at once.

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In the past, among other things, water was not hyper
turbid. If we know exactly what caused this, we can better
predict the effect of future interventions.

You are developing a model of the Dollard and the Ems
to gain a better understanding of the processes at work.
What kind of model is this exactly?
Large numeric models are already being used by the
Directorate-General for Public Works and Water Management
and the Deltares applied research institute among others.
However these models are not tailored to the situation in theEms. As mathematicians, we are developing a new model thatcan be seen as complementary to the numeric models. One of
the ways we are doing this is by looking into the past. The water
was not hyper-turbid in 1965 and the area was ecologically
healthy back then. We are curious to know what has happened
since. If we know exactly what caused the turbidity, it will help
us predict the effects of future interventions.

How do you know what the situation was in 1965?
It was anything but easy to find out. We didn’t know if any data
was available, so we just drove to the German city of Emdenand tried our luck. We ended up in an archive in an attic withcupboards full of stacks of paper. It was a wintry day, there
was no heating in the attic, and it was cold and draughty. We
leafed through the papers, hoping to find something useful.
And we did! We found tidal data from 1965; the numbers had
been written by hand on a large sheet of paper. We also foundsoil maps with depth indications and samples of soil profiles
from various years. We were very happy with this information,
because it allowed us to reconstruct the situation in 1965.
We discovered that in later years, and in particular from the
1980s onwards, the river became deeper and deeper and there
was less underwater friction. The increase in silt made theriver bottom muddier but also smoother. This resulted in lessturbulence and other water movement, which was also reflectedin the water levels. In 1965, the water level on the seaward side
was higher than inland. It’s now the other way round.

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About Henk
Henk Schuttelaars (1970) graduatedUtrecht University in 1993 witha degree in physics. He obtained his
doctorate at the same university in1997 on the analysis of underwater
soil patterns. He then participatedin various projects at TU Delft andUtrecht University as a post-doc.
Schuttelaars has been associate
professor at TU Delft since 2006.
He is currently building a new model
to develop a better and more detailed
picture of how silt behaves in theRiver Ems and the Dollard inlet.
He hopes this will allow a better
understanding of how silt hasdeveloped in the Ems estuary.

Photo: Herman Verheij

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How did these discoveries improve your model?
We now have a better understanding of which processes played a role. Our model can describe
what has changed between 1965, our baseline, and today. This will also tell us more about therole of turbulence and friction underwater during this period. When the river was made deeper,it also meant more sediment was introduced into the system. This decreased friction and

The survey involves a large number of parties
mainly from the Netherlands and Germany. It isbeing coordinated by the Directorate-Generalfor Public Works and Water Management andRoyal Haskoning, but TU Delft, the universities
of Oldenburg, Maine and Rostock (Warnemunde)and many local authorities are involved too.
What is it like to work together with so manydifferent parties?

You were on board one of the research vessels
during the survey. What was that like?

We need all these partners, because otherwise weperiod of three months. It’s easy to think up a plan likecannot produce a complete picture of the estuary.

that sitting at your desk just because you want theThis is a huge project that encompasses a large region

information, but it’s not really something you’d ask

in two countries and involving an enormous number ofpeople to do, to work for so long on a project. I alsomeasurements. That costs a lot of money, so you canenjoyed talking with the captain. While on board, I

only do it if you join forces. For example, we are using

noticed that parts of the river flowed constantly while

vessels provided by partners and highly specialised

other parts did not. The captain explained that this ismeasurement equipment. We get together a few

common and is caused, among other things, by small

times a year to discuss progress and participate inrivers branching off from the main flow. I was surprised

workshops. I know almost everyone involved and we all

to learn this. We spend all our time measuring andwork together well. We’re now waiting for the data frommaking calculations about the Ems, mainly searching

the most recent survey to be processed. We’ll importfor patterns, and so we view the river as a single

this data into our model too, and of course use it insystem. By sailing with a survey vessel, I gained new

publications. Similar areas such as the Scheldt estuary

insights and came to see the river in a new light.

I sailed with one of the boats for three days. One of
the measurements lasted 13 hours. We measured silt
concentrations, among other things. I had to pull up abottle filled with water once every twenty minutes. This
gave me even more respect for the people who do thiswork on a daily basis. It is hard work on board. Ideally,
I would have preferred to have collected data over aand some regions in Asia where heavy dredging takes
place could also profit from our findings. It is in all ourinterests to cooperate, because it decreases costs andinconvenience, the river will be made safer and we’ll
generate knowledge we can all use.

turbulence which in turn led to more sedimentation. This was the cause of the extremely highsediment concentrations. There are other aspects, though, which we’re still unaware of, such as
the influence of the sediment on the mixture in the water column, from the surface of the water
to the bottom of the river, and how this changes under the influence of the tide.

In early September, a major survey was carried out involving no less than eight ships
all across the Ems. How important was this?
One of the things the survey measured was the influence of the tide on the transport of silt.

'Henk is studying various factors that all influence the transporting of silt. One of these is the distribution of
sediments throughout the water column; for example from the surface of the water to the bottom of the river.
He also wants to find out where the silt is entering the water and we are examining what happens under hyperturbid conditions, which occur when a large amount of sediment collects in one place in the water.'

We can use this information to improve our model. It’s an interactive partnership; we can tell thesurvey team what information we need and then input the results into our model to improve it.
That is why the September survey focussed on what happens to the silt in the river under the
influence of the tide. Of course, the survey gathered a lot of other data too. We used special
vessels to measure the water velocity, silt and salt concentration, and turbulence. Four ships
were anchored in one place, while three others sailed back and forth across the flow of the river.
One boat went from Papenburg in Germany and sailed downstream through the Ems estuary
and into the Dollard inlet. This provided us with information about specific sites, but also about
possible differences in the water over a long distance.

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From micro to macrowith duality

17

Text: Merel Engelsman | Photography: Mark Prins

Reality, how do we get there? We know how certain features of ourmacroscopic everyday world unfold and we capture these in mathematicalformulas, but often these explanations do not have a basis in the microscopic
world of colliding and randomly moving molecules. Frank Redig wants tounderstand the relation between microscopic and macroscopic reality, inparticular for non-equilibrium systems. He was awarded an NWO TOP1-grant
for his research into the conditions that must be met by a model of a nonequilibrium system, for it to be mathematically solvable using a powerful
technique called duality.

Mathematicians and physicists use models‘Non-equilibrium means thatthe reversal of time results ina different movie being shown.
For such systems, we try tomathematically explain how
macroscopic laws emerge fromthe underlying microscopic
world.’

to describe reality and to try and understandit. Models are simplifications of microscopic
reality, but sometimes they allow us to derive
macroscopic laws of physics and to provide
explanations for natural phenomena. For
example, the freezing of water at a certain
temperature or why certain materials can beturned into permanent magnets. These are,however, examples of systems in equilibrium.
Models of non-equilibrium systems are often
not mathematically solvable, and there is no
general theory linking the micro-world to themacro-world, such as the Boltzmann-Gibbs
distribution for systems in equilibrium.

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Behind the formula‘The physics of non-equilibrium phenomena is predominantly
undiscovered territory,’ says Frank Redig. ‘We know what

About FrankFrank Redig completed his
MSc and, in 1992, his PhD at

happens at equilibrium, and close to equilibrium, but not

the University of Antwerp. He

far away from it.’ He explains that a metal rod, of which

subsequently spent six years

both ends have a consistent but different temperature, isa good example of a non-equilibrium system. ‘We know theformula that describes heat conduction from the hot end of
this rod to the cold end. This formula can be easily deduced
from the law of the conservation of energy and the fact thatheat flow is proportional to the temperature gradient. But
this is a phenomenological description. What is lacking isa mathematical proof based on a model of the underlying
microscopic world of individual vibrating atoms. I want

as a monk and two years as
a postdoc. From 2000 till 2005
he was assistant professor at
the Eindhoven University ofTechnology, followed by four
years of associate professorshipat Leiden University and an
appointment at the Radboud
University Nijmegen. As of 2011

to understand the emergence of the macro law from themicroworld. How does the time evolution of the degrees of
freedom of these individual atoms result in the heat flow?
To develop such a proof, my colleagues and I apply statisticalmodels that are simplifications of the microscopic quantum
world.

he is full professor in Applied
Probability at the Department
of Applied Mathematics of theFaculty of Electrical Engineering,
Mathematics and Computer
Science of the Delft University ofTechnology.

Boltzmann-Gibbs distribution

Model

The Boltzmann-Gibbs distribution is a probability distribution

A model is a mathematical representation of a physicalof the microstates of a system in thermal equilibrium. The

system. For example, particles jumping independently, and at

higher the energy of a microstate, the lower the probability

random intervals, on a two-dimensional lattice. Or a chain ofof this state to be occupied or present. The probability

particles connected by springs to their nearest neighbours.

of a high-energy microstate increases with increasing
overall temperature of the system. The Boltzmann-Gibbs
distribution provides the exact compromise between
maximum entropy (amount of chaos in a system) andminimal energy.

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Many models, few solutions‘To study thesesymmetries, theresearchers use
the so-called
Lie-algebraic
approach.’‘A prerequisite of the systems we investigate is that there isa conserved quantity. The total energy in the system, forexample, or the number of particles,’ says Redig. Even though
the models are caricatures, and simplifications of the physicalreality, most of them are not mathematically solvable. But if
certain specific conditions are met, it may be possible to findan exact solution using duality. ‘Most dualities so far have beenfound ad-hoc. Suddenly people found a much simpler systemthat could be connected to a certain non-equilibrium system.
What we have developed is a constructive mathematical theory
that can explain why certain models can be solved with duality
and others cannot. It also tells us how to constructively findthese systems and the corresponding duality functions.’

Powerful symmetry

Microscopic wealth
An important aspect of their research programme is the application of their
theory to inhomogeneous systems, such as impurities in the metal rod
mentioned earlier. ‘Nearly everything in the world is inhomogeneous,’ Redig
explains. ‘It only appears to be homogeneous when observed at a certain scale.
Just like Redig’s interests, the application of duality is not limited to fundamental
physical processes. ‘Think of the distribution of wealth in our society. The
same mathematical models are applicable, because ‘something’ (money) is
distributed while the total amount is conserved (if you look at the correct time

‘We hope todiscover equations
describing amacroscopic
system ofneurons.’

scale). The fact that someone in the USA may handle money differently fromsomeone in the Netherlands, can be modelled as a form of inhomogeneity.
Through the ages, the distribution of wealth has satisfied the Pareto-distribution,
80% of wealth for the 20% most wealthy people. I want to know if a microscopic
theoretical explanation exists, just as it does for the distribution of particle
speeds in idealized gasses.

The mathematical formalism used by the researchers, is at
a higher level of abstraction than duality itself, and depends
on the presence of additional symmetries in the models. To
study these symmetries, the researchers use the so-called
Lie-algebraic approach. According to Redig ‘this approach does
not only indicate if duality is possible, it even automaticallyprovides all duality functions. Depending on what you areinterested in – the physical current, the number of particles,
etc. – you only have to pick the appropriate duality function.’
In a collaboration with Frank den Hollander from Leiden

DualityNon-equilibrium

Under certain conditions, a model that is not mathematicallyNon-equilibrium means that the movie of a physical systemsolvable may be ‘linked’ to a simpler model that typically has

looks different if you reverse time. A flow is present. In an

no physical meaning but that is solvable. The link between

infinitely large hourglass (sand timer), the same number ofthese two models is the so-called duality function.

grains of sand will pass the narrow opening each second.
If you reverse time, the grains will no longer fall downward

University and Cristian Giordinà from the University of Modena

but upward.

and Reggio Emilia (Italy), Redig received a TOP1-grant from
NWO to further develop and apply this methodology.

Dreamlike improvisation
Duality can also be applied to biological systems – the conserved quantity being
the population size. Think of how population characteristics develop over timethrough evolutionary forces such as mutations, selection and migration. Though
speculative, even human consciousness may be a consequence of a micro-tomacro transition, related to the physics phenomenon of a phase transition.
‘A single water molecule does not freeze, but a large number of such molecules
can undergo a phase change from liquid (water) to solid (ice). This phasetransition can be mathematically explained by applying the thermodynamic
limit – an unlimited number of particles in an unlimited volume. The same may
be true for various phenomena in the brain. We hope to discover equations
In an infinitely large hourglass (sandtimer), the same number of grainsof sand will pass the narrow opening
each second. If you reverse time, thegrains will no longer fall downward
but upward.

112

describing a macroscopic system of neurons.’ This would mean that Redig,
who thinks of both his mathematical work and his hobby of playing the piano as
dreamlike improvisation, would possibly reduce his own creative processes toan equation.

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Affordable MRI
Text: Annelies de Bakker | Photography: Mark Prins and Io Cooman

18

Modern MRI scanners for disease detection are commonly usedin the West but in developing countries hospitals are simply
unable to afford them. Mathematician Martin van Gijzen ispart of a team helping to develop a simple MRI scanner fora children’s hospital in Uganda. ‘Suddenly I am learning allabout hydrocephalus.’

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SCAN!

The joint venture of Rob Remis (Circuits & Systems), Martin van Gijzen(Numerical Analysis) and Andrew Webb (LUMC) is a great example of a fruitfulcollaboration. This video describes the partnership between Rob, Martin and
Andrew.

‘This scanner is specificallyused to detect hydrocephalus
but the design, the magnet
and the algorithms can also
be used to diagnose otherdiseases.’

Our aim is to develop a simple scanner which
will cost no more than fifty thousand euros.

A simple MRI scanner can play a vital role in

Weak magnet, complex algorithm

Using a weaker magnet makes the results of

The partnership with British MRI physicist

the diagnosis of hydrocephalus, a condition

Van Gijzen goes on to explain his role: ‘A

the scan less accurate. That means it is very

Andrew Webb, American neurosurgeon

that affects over a hundred thousand children

normal MRI scanner has a superconducting

important to gather as much information as

Steven Schiff and Ugandan biomedical

in sub-Saharan Africa. An early diagnosis

magnet and liquid helium for cooling. It

possible via other methods,’ Van Gijzen says.

engineer Johnes Obungoloch is a truly

can prevent severe brain damage. ‘Once

produces a complete, high-resolution picture.

‘For example, better images can be madeinternational one, which, Van Gijzen says,

the outward signs of the disease manifest

But scanners like this can cost up to three

if we also use features indicative of hydro­

gives it something even more special.

themselves it is usually too late,’ Van Gijzen

million euros and it takes highly specialised

cephalus. By using all the data and combining‘Andrew Webb works at LUMC and is a world

says.

knowledge to operate them. Our aim is toimages a simple scanner will, in the end, give

specialist on MRI. Steven Schiff is headdevelop a simple scanner which will cost no

us a fairly accurate reconstruction.’of the Neuroengineering Department of

Van Gijzen’s field is numerical linear algebra,

more than fifty thousand euros.’ The reason

or the algorithms behind technical applicati-

it can be made so much more cheaply, Van

Multidisciplinary and intercontinental

ons and simulations. He deals with numbers

Gijzen says, is down to the use of a weak

Apart from the mathematical aspect thein Uganda. Johnes Obungoloch is vice-

and abstractions and the results of his work

magnet. ‘This means the mathematical side

project is also an educational one for Van

dean of the new biomedical engineering

are often not immediately obvious to theof things is much more complicated and that

Gijzen. ‘I come into contact with fields I am

department at Mbarara University in Uganda.

outside world. ‘Writing a scientific article

is what we, that is what my colleague Rob

not very familiar with, medicine, for instance.

A very diverse and inspiring group of people

or developing an algorithm clearly matters

Remis and PhD students Merel de Leeuw den

And I am learning a lot about hydrocephalus,

to work with!’to science but this project also has a much

Bouter and Xiujie Shan are working on.’which is very interesting. At Delft I am also

more direct social objective. It helps find aworking with the DEMO engineers who aresolution to a major problem in the developing

responsible for the hardware. So you see

world, one that involves children as well.’

I’m not just staying in my own mathematical

Pennsylvania State University and manages alarge research programme on hydrocephalus

bubble.’116

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The team
From left to right: Merel de Leeuw den Bouter,
Martin van Gijzen, Xiujie Shan, Rob Remis.

‘At the start of the project, we were developing our first MRI‘By using all thedata and combining
images a simple
scanner will, inthe end, give us
a fairly accurate
reconstruction.’scanner together with LUMC. That scanner never yielded
images of sufficient quality. But we learned a lot from it.
Based on the lessons learned, LUMC designed a new proto­
type that does give images. Together, we are improving their
quality, both by image processing techniques and hardware
improvements. We expect that this prototype will be ready for
replication at MUST, our partner university in Uganda, in 2020.

Contribution to the medical science in developing
countries
Now the prototype is successful there will be a number ofother challenges that will have to be overcome. The scannerneeds to be able to withstand temperature changes andmust be easily transportable to remote areas. The design
also needs to take into account that babies tend to movetheir heads a lot. ‘And of course it’s important that doctors in
Uganda can operate the scanner and that there are specialists
on the ground to maintain it.’
Although the first phase of the project has taken place mainlyin the Netherlands and the US, Van Gijzen says its ultimate
goal is to broaden the base for medical science development
in developing countries. ‘The techniques and software will be
publicly accessible. This scanner is specifically used to detect
hydrocephalus but the design, the magnet and the algorithms

This scanner is specifically used to detect
hydrocephalus but the design, the magnet andthe algorithms can also be used to diagnoseother diseases

118

can also be used to diagnose other diseases. In time thescanner will be manufactured locally. Most diseases are notthat difficult to detect but you do need the right equipment.’

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19

Organizing high-dimensional
data with triangles and fields
Text: Merel Engelsman | Photography: Thierry Schut‘The mathematics of algorithms and scalability problems.
That’s what makes my heart beat faster,’ says Nicola
Pezzotti, former PhD-student in the Computer Graphics andVisualization group. He thinks of himself as an archetypicalcomputer scientist, but the first ten minutes of our interview
he highlights a number of practical applications of his work,with great enthusiasm. In a collaboration with the LUMC hediscovered new cells of the human immune system. They also

Fast rendering of triangles appears to have little in common withidentified new differentiation stages of stem cells. ‘Our dataneural networks. They are, however, linked by a clever insight byvisualization indicated their existence. Knowing what to look

Nicola Pezzotti. Exploring the similarities in high-dimensionalfor, the LUMC researchers were able to detect these cells.’ The
most important application of Nicola’s research, however, is thedata through visualization no longer takes tens of minutes on avalidation of neural networks. Some background knowledge

fast computer. The required computations can now be handled inis required to understand his work on the t-SNE algorithm

real-time by a web browser. His breakthrough research is ideally‘The mathematics
of algorithms andscalability problems.
That’s what makes
my heart beat faster.’t-distributed Stochastic Neighbor Embedding.

suited for the validation of neural networks. But biomedical
researchers at the LUMC are eager users as well.

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Many dimensions
Nicola’s work isn’t so much focused on big data, as it is on

About Nicola

high-dimensional data. ‘This means that each data point has

Nicola Pezzotti is a researcher focusing onvery many characteristics,’ says Nicola. ‘In the LUMC they can

the development of algorithmic solutions.

determine the presence of tens of different proteins on the‘My algorithms and tools are used in several

surface of individual cells. That makes each cell a data point

research groups and led to discoveries

with tens of characteristics.’ Visualizing these data would

presented in important venues such as Nature

require tens of dimensions, something humans can’t handle.

Communications, Nature Immunology and the

Other examples of high-dimensional data are pictures of

Journal of Experimental Medicine. I do not focus

animals or hand-written numerals. When digitized, a computer

only on fundamental research, but also on

can process and organize these. But with each pixel a variable

the development of large, scalable and stable(color, intensity, etc.), each data point has up to thousands ofsoftware and its path to useful products.’ Aftercharacteristics.

his masters, he worked for more than three years
in an Italian start-up developing 3D scanners.

Warping space

From September 2014 to October 2018, Nicola

Whether it be the recognition of pictures of animals or the

did his PhD at TU Delft. At the moment of

discovery of genes that may play a role in developing breast

publication of this volume, Nicola is currently

cancer, deep neural networks are the power tool to findworking at Philips. ‘As a research scientist in

similarities in such high-dimensional data. ‘After a neuralArtiﬁcial Intelligence, I lead the development of

network has been setup for a particular application, it has tomachine learning solutions for image formation

be trained,’ Nicola explains. ‘This requires a large set of training

in MRI. Among the other duties, I set up twodata. Pictures of animals, for example. The network will lookresearch teams in collaborations with academic

for similarities that we know or suspect to exist.’ The goal

institutions.’

could be for the network to differentiate between a parrot,
a pigeon and a giraffe. You tell the network what each training
picture represents, and it will look for the characteristics that,apparently, fit this description. ‘Colorful’ can be one of thedescriptive characteristics for ‘parrot’. ‘You can think of a neuralnetwork as warping high-dimensional space,’ says Nicola.
‘Pictures of the same animal will then form high-dimensional
clusters, even if there is quite some distance between thesedata points in the unwarped space. When the network has been
trained, it will be able to instantaneously label any new picture
based on its location in high-dimensional space.’

An elephant is not a pigeon‘A visual representation
is an effective method
to judge the quality of aneural network.’

It is, however, a bit more complicated. ‘The output of a neuralnetwork is also high-dimensional,’ Nicola explains. ‘It is a seriesof numbers, a so-called feature vector, with each number aprobability.’ The first number may be the probability of the
new image being a parrot, the second number the probabilityof it being a pigeon, and so on. All these probabilities add up
to unity, to one hundred percent. ‘If the network hasn’t been
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various animals,’ Nicola explains. The network may then label‘It is essential thatthe low-dimensional
representation
preserves thecharacteristics of thehigh-dimensional data,such as their clustering.’

all parrots and pigeons, or all winged creatures, as one and thesame animal. And if the pigeon is the only gray animal in the
training set, it may label an elephant and rhinoceros as such.
Developers also want to compare two or more neural networks.

If the network hasn't been
properly designed or trained,
it can't distinguish between
the various animals.

Which one is best-suited for the task? ‘A visual representation
is an effective method to judge the quality of a neural network,or to determine whether or not more training is needed,’says Nicola. Humans can only deal with up to three spatial
dimensions. Therefore, plotting the (warped) high-dimensional
space ‘within’ the network is not an option. But certain
algorithms can provide insight into the similarities that exist
in a high-dimensional data set, such as the output of a neuralnetwork. Nicola’s research focuses on the t-SNE algorithm,
which is especially well-suited for this task.

Back to two dimensions
In 2008, Laurens van der Maaten - a former associate professor of TU Delft and now researcher
at Facebook AI - published his t-SNE algorithm as an improvement of the existing SNE algorithm.
The goal of both algorithms is to visualize the similarities in a high-dimensional data set bymeans of a representation in a reduced number of dimensions. ‘This can be a three-dimensional
representation, but in my work, I focus on the representation in a two-dimensional plane (2D),’
says Nicola. ‘It is essential that the low-dimensional representation preserves the characteristicsof the high-dimensional data, such as their clustering.’ Nicola explains that the t-SNE algorithm
is a two-step process. Imagine a dataset of a few hundred thousand feature vectors, the resultof feeding pictures of animals to a trained neural network. First, the algorithm determines the(high-dimensional) distances between all feature vectors. Data points that are alike, with little
distance between them, will form a cluster in high-dimensional space. Second, the algorithm
uses a process of optimization to search for the 2D-representation of all data points that best
matches these high-dimensional distances. Data points that are alike should be clustering in 2D
as well. Likewise, there should be large 2D distances between data points that are not alike inhigh-dimensional space.

Attractive and repulsive forces

Einstein’s gaze

The algorithm translates the distances between data

Nicola’s most recent and breakthrough insight,

points into attractive and repulsive forces. The more

however, relates to the computing of the repulsive

similar two data points are, the larger the attractive

forces. This was the only remaining time-consuming

force. ‘All data points are at least somewhat similar,’component of the algorithm. He perfected andsays Nicola. ‘It is therefore important to have a

implemented his insight during an internship at

repulsive force as well, or all points may end up

Google’s Zurich office. His peers in visual analytics

forming a single blob.’ The original SNE algorithm was

are more than enthusiastic. One fan twitters aboutslow because it calculated both forces between all‘new research from a clerk in our Bern office,’ thereby

data points. ‘In this case, the number of calculations

referring to Einstein, who developed his theory ofof distances and forces scales quadratically with thespecial relativity during his time at the Swiss Patent

number of data points, as does the computing time,’

Office in Bern. A comparison with Einstein is typically

Nicola explains. ‘And you need many data points toflawed, but there certainly are similarities between

get an intuition for the quality of the neural network.’

Nicola’s work and that of Einstein. ‘Point to point

It is this quadratic explosion in the number of calcu-

interaction is the standard way to see the t-SNE

lations that makes the t-SNE algorithm a scalability

optimization problem,’ Nicola explains. ‘You typicallyproblem, one to which Nicola is particularly drawn.

do not want to change the dominant paradigm.

Over the years, the original SNE algorithm has been

I decided to replace the point to point calculations

improved a number of times. The t-SNE implementati-

for the repulsive force with the idea of a ‘field’.’on by Laurens van der Maaten limited the calculationof the attractive forces to those points already in close

In Nicola’s approach, each data point in theproximity. ‘The attractive forces are very small for data

2D-representation projects a repulsive force onto a

points that are unalike, that are far-removed. They cansquare piece of ‘space,’ thereby creating a small field.

Once training has been completed, a neural network can instantaneously classify new

therefore be ignored,’ Nicola explains. It was Nicola

Other data points that are in close enough proximity

data. It can, for example, label a single subsequent picture to be ‘a parrot’. The t-SNE

himself who recognized that the distances between

will experience a repulsive force because of this field,

algorithm visualizes the similarities within a high-dimensional dataset. Its output is a

the high-dimensional data points could be calculated

and vice versa. Instead of calculating all these forcesgraphical representation of clusters of data points, without any indication whether awith some inaccuracy. ‘This dramatically reduced the

between data points one by one, Nicola sums up all

cluster represents, for example, ‘birds’ or pictures of ‘a parrot’.

computation time without sacrificing the end result.’

small fields into a global field in the two-dimensional

Neural networks versus t-SNE

space.

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2020 | EEMCS NODES VOLUME II125

At some locations these small fields may add up toeach data point (see figure) consist of two textured

analyzing neural networks. ‘It is important to me

to independently enter and analyze their researcha very strong global field, at other locations the global

triangles. Graphical processors have been optimized

for software to be open source and readily usable

data.’ The applications of Nicola’s work are, however,field may be much weaker or even be negligible.

to process such triangles at a very high speed. As aby anyone. My software should not require a large

not limited to neural networks and the biomedical

Subsequently, Nicola determines the repulsive force

result, Nicola’s implementation of the t-SNE algorithm

computer infrastructure that only universities andfield. A master’s student used his algorithm to analyze

to each individual data point. This force depends onlyis about a hundred times faster than any previous

companies can afford and maintain. I wanted mybaseball player statistics. Nicola himself applied it toon the location of a data point within this global field.

implementation. A researcher can now observe thealgorithm to be fast enough to be run on a single

analyze social media filter bubbles. All that is needed

The field and the resultant forces are recomputed

optimization process in real-time, even within a web

desktop computer.’ Nicola also published his research

now, is an algorithm that clarifies my electricity bill.

during each step in the optimization process. In its

browser, rather than having to wait tens of minutes

in scientific journals, but even that doesn’t satisfy him.

final implementation, the algorithm creates three

to see the end result. ‘My implementation can handle

For someone who is not an expert, analyzing high-global fields; for the horizontal repulsive forces, for the

much larger datasets, and the real-time visualization

dimensional data still is a very difficult task. ‘I am lucky

vertical repulsive forces, and a normalization field thatprovides additional opportunities. A researcher can

to be part of a research group that consists of many

ensures a smooth optimization.

interrupt the optimization process at any moment toexcellent and highly motivated computer scientists,

decide on additional training of the neural network, oreach with their own specific interests.’ His colleague

to zoom in on a specific cluster for additional detail.’

Thomas Höllt is building a software platform, named‘It may seem that my algorithm performs unnecessary
computations as it calculates fields at locations

Cytosplore, that bridges the gap between the algorithm

where there are no data points. But the fields have

Publicly available

a very low resolution and, more importantly, theNicola’s algorithm has been incorporated intomuch more than a graphical user interface on top of

approach is ideally suited for implementation on a

Tensorflow.js, Google’s open source software platform

some data processing routines. Thomas listens tographical processor.’ The square fields surroundingfor – among other things – designing, training andtheir exact needs and creates a tool that allows themand the biomedical researchers at the LUMC. ‘It is

Normalization Term
Exploding complexity:

Horizontal Shift

Vertical ShiftMax

The original SNE algorithm computed forces between all data points.
Having three data points, there are three forces to compute; between the points A-B, A-C
and B-C.
Having four data points, there are six forces to compute (A-B, A-C, A-D; B-C, B-D; C-D).
Having ten data points, there are 45 forces to compute.
Having N data points, there are (N•(N-1))/2 = (N2-N)/2 forces to compute. The
computational complexity scales with N2.

MinHaving (only) 10,000 data points, there are nearly fifty million forces to compute!
For an acceptable calculation time, even for large data sets, computer scientists try tofind solutions that scale with N or, at most, with N•log(N).
Replacing forces with a field is very similar to what Einstein did. He replaced thegravitational force – between planets, stars and other objects – with curved spacetime.
In his theory, the gravitational force experienced by any object is a result of the local
curvature in spacetime.

126

A magnified representation of thethree fields that each data point
projects. The data point would be in
the center of the three images. In thetwo images on the right, a negativevalue (blue color) represents arepulsive force directed towards theleft or downward.

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So much more than 3D
visualisation

20

Text: Merel Engelsman | Photography: Mark Prins

In recent months, EEMCS scientists Elmar Eisemann and Ruben
Wiersma attracted a lot of attention with their three-dimensional
augmented reality experience of a work by 17th century painterPieter de Hooch. This is just the beginning of how mathematics andcomputer graphics will enhance our perception of art.
‘I like to tell stories, using film or plain text,’ Ruben Wiersma‘There are similarities
between the work of the Dutch
Masters from the Golden Ageand some of the researchgoals of our group.’says, ‘but the medium of computer graphics adds entirely new
possibilities.’ The essence of a story is not so much in thebeauty or realism of its setting, but in the message it conveys.
It would therefore be too simple to characterise their 3D
visualisation of the painting Woman with a child in a pantry as
a gimmick, as a modern-day twist applied to a 17th century
piece of art. ‘Pieter de Hooch paid a lot of attention to linear
perspective to add depth to his paintings, just like his contem­
porary, Johannes Vermeer,’ Wiersma explains. ‘We specificallyhighlight this aspect of his work. We use computer visualisation
to tell the story of De Hooch and his use of perspective.’

The overlap between art and science
SCAN!

The idea for their visualisation is rooted in the organisation,by the Foundation Delft in-Ovatie, of an exhibition of the workby Pieter de Hooch, who resided in Delft from 1652 to 1661.
Elmar Eisemann, professor in the Computer Graphics andVisualisation group at TU Delft, was one of the scientists
approached by the foundation for a symposium to be heldin parallel to the exhibition. He more or less succeeded in
combining his love of mathematics with his childhood dream of
becoming a Disney illustrator. ‘There are similarities between thework of the Dutch Masters from the Golden Age and some of
the research goals of our group,’ Eisemann explains. ‘They weremasters of light: the incidence of light, shadows, indirect lightingof surfaces, transparency, the accurate portrayal of complex
materials such as clothing or metal objects. Within our researchgroup, we aim to achieve a similar realism using computers, andto achieve this as efficiently as possible. Sometimes we have todevelop completely new physics models.’

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How did the De Hooch visualisation come to be

horizon towards the same vanishing point.

between the characters in the painting and youFirst, each pixel was assigned a value for its depth, using an existing machine learning tool and the software‘To strictly apply this perspective, De Hoochas an observer. We think De Hooch may havefor manual depth annotation as developed by the researchers themselves. They subsequently transformed

marked such a vanishing point with a pin toapplied this false perspective intentionally.’

this depth map into a three-dimensional model inspired by the perspective as used by De Hooch. The model

which he attached a piece of string serving

had to be simplified as the augmented reality toolkit of the phone

as a construction line,’ Eisemann says. ‘In

A different perspective on art

would otherwise not be able to provide a smooth experience. Usingsome paintings you can uncover this tiny hole

The researchers also noticed that De Hooch

the phone’s camera, this toolkit projects the three-dimensional model

underneath the layers of paint using x-ray

often had his virtual horizons coincide withon top of (the image of) the painting, allowing the observer to moveimaging techniques.’ At first, the researchers

objects in the painting, such as the seataround the scene.

tried to reconstruct these vanishing pointsof a chair, a table top or a windowsill. The

by hand, just like many art historians still do.

algorithm also exposed composition lines

This turned out to be very time consuming aspresumably used by the painter to arrange

it required extreme precision. They therefore

the scene and to direct the observer’s gazewrote an algorithm that automatically extracts– a nobleman’s pipe pointing at the eyes ofVarying rules of perspective

Pinning down the perspectivelines and vanishing points from a painting.

the servant maid near the opposite edge of

De Hooch often painted the same scene

The characteristic feature of linear perspective‘It turned out that, next to multiple vanishing

the painting, or a lower leg pointing at thetwice. ‘At first, our idea was to make a 3D

is that it uses one or more vanishing points

points, De Hooch also used multiple horizons,’

pinnacle of a church tower. Quite often, De

reconstruction of a room using both paintings,’

located on a real or imaginary horizon (seeEisemann explains. ‘A room appears to be

Hooch marked such composition lines with

Eisemann says. ‘That didn’t work out well, as it

figure). Lines that run parallel in the realmuch larger when the central vanishing point

light and dark accents. ‘All this information

turned out that De Hooch didn’t always apply

world, such as the seams between tiles orof the floor is located below the ‘real’ horizon.

came to light using a very simple line

linear perspective very strictly. Sometimes hethe edges of a table, appear to recede to theIt also increases the perceived distancedetection algorithm, and it already tells us anpainted somewhat freely or at least applied

intricate story of how the artist composed his

different rules of perspective. We then decided

paintings,’ Eisemann explains. The augmented

to specifically focus on his use of perspective

reality experience is only a simple application

for adding depth. It fit well with our ongoingof the actual scientific research performed

work in computer graphics in which we, forin the Computer Graphics and Visualisation

example, showed that you don’t need to haveGroup. Based on their reaction, the visitors

maximum accuracy in depth for a scene toof the exhibition and the symposium weren’t

be perceived as being realistic. We had also

any less impressed. ‘Some visitors told us

already developed software to transform athat they can no longer look at a painting

two-dimensional image into an interactive
three-dimensional scene, requiring only very
little user input. That’s how we came up with
the idea of developing an augmented reality
experience for the De Hooch exhibition.’

About Ruben
Ruben Wiersma recently started as a PhD
candidate at the Computer Graphics andVisualization group. His interests include
graphics, machine learning, and art. Ruben

About Elmar

130

will start working on extending his MSc thesis

Elmar Eisemann is currently heading the TU

research into geometric deep learning for

Delft Computer Graphics and Visualization

publication and, in his PhD research, will workgroup, and he received the Dutch Prize foron computer graphics and machine learning

ICT Research 2019 for his research into theapplications for painting analysis underaccurate, detailed depiction of visualisations

supervision of Prof. Dr. Elmar Eisemann andusing modern graphics hardware.

wProf. Dr. Joris Dik.

2020 | EEMCS NODES VOLUME II

131‘Imagine that we employ the full powerof artificial intelligence and computervisualisation to enrich the experience andunderstanding of art lovers.’

size using mathematical techniques. He will
also apply advanced computer visualisation
techniques to present his scientific findings
to both experts and laypeople. ‘The end goalof my doctoral research is the developmentof algorithms that can be used for any painting‘I find it interesting to apply mathematicalprecision in an area that, typically, is a bit
less exact, a bit more elusive.’by any painter, and in any museum, such as
the Mauritshuis and the Rijksmuseum.’

Art, not artificial
The question remains whether the researchof Eisemann and Wiersma may somehow
diminish the magic of art. ‘Actually, we add
magic,’ Wiersma says. ‘The presentation ofart nowadays is very factual and scientific.

The research into the use of perspective byPieter de Hooch was a collaboration between
Elmar Eisemann (professor), Ricardo
Marroquim (assistant professor), Ruben
Wiersma (doctoral student) and Yoann
Coudert-Osmont (visiting student), all within
the Computer Graphics and Visualisationgroup at TU Delft.
A three-dimensional visualisation of thepainting Woman with a child in a pantry by
Pieter de Hooch. In augmented reality, acomputer adds objects and information
to a live image of reality. In this case, theiPhone replaces the image of the painting
by a three-dimensional representation. This

without wanting to find the imaginary horizons

specifically focusses on the use of computer

They show you an x-ray image or a sample ofand vanishing points,’ Eisemann says. ‘And agraphics for the analysis of paintings.

the paint that was used. We can present this,photographer who didn’t like the paintings by‘I am a frequent visitor of museums and thisand so much more, in an exciting manner,

De Hooch, because he intuitively grasped theresearch is a good fit to my general interest

increasing the observer’s connection toperspective to be off, now wondered how toin art,’ Wiersma says. ‘We will use modern

the piece of art.’ Eisemann adds that thisuse false perspective in his own work. Imagine

data analysis techniques, such as machineresearch is certainly not purely driven bythat we employ the full power of artificial

learning, to increase our understanding of

the technical challenge. ‘I find it interesting

intelligence and computer visualisation topaintings. Think of an even more profound

to apply mathematical precision in an area

enrich the experience and understanding ofanalysis of the use of perspective, of thethat, typically, is a bit less exact, a bit more

art lovers.’ That is exactly what Wiersma andunderlying layers of paint and of the colour

elusive. Our De Hooch visualisation stimulated

Eisemann intend to do.

palette used. The researchers teamed up withthe observer to have a deeper experience

Professor Joris Dik, professor of Materials inof his use of perspective.’ Both researchers

you: ‘I believe that art is communication

Art and Archeology at the 3ME Faculty. Overstress the importance of having a continual

between people. It is meaningful only because

Immediately after obtaining his cum laude

the past decade he has used and improved

discussion with the art community as tothe person observing it has emotions,master’s degree, in October last year, Wiersma

x-ray techniques to non-destructively dissect

the use and added value of their research.

memories, experiences, that allow him or her

started with his doctoral research, again in thepaintings, layer by layer. Such an analysis

Should you still have doubts about their use of

to empathise. This is why art, by definition,group of Eisemann. This research is partiallyresults in massive data, which Wiersma

computers to analyse paintings then, perhaps,

is something uniquely human. A computer

financed by the Delft University Fund andintends to reduce to a more manageable

Wiersma’s personal opinion will reassurecannot diminish that.’

Combined with x-ray imaging techniques132

2020 | EEMCS NODES VOLUME II

representation updates in real-time whenever
the phone changes its position or viewing
angle relative to the image.
As an homage to the play with perspective of
De Hooch, the application strikes a balance
between a 3D reconstruction and the flat
appearance of a painting.

133

How not to waste energy
on 5G

21

Tekst: Merel Engelsman | Foto: Marcel Krijger

From an energy point of view, humanity’s insatiable hunger formobile data is unsustainable, unless you’re willing to break a
few long-held believes in the field of wireless communication.
Professor Earl McCune was geared up to do just that.

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135

Many bits of energy make a big problem
You may be jumping with joy when your mobile phone provider quadruples your data planeach year, for the next five years. A thousand times more data sounds great. ‘But there isalways a cost,’ says Earl McCune, professor in the Electronic Circuits and Architectures group at
TU Delft and specialized in sustainable wireless systems. ‘All of the systems needed to provide
these services, available on demand, draw power. The digital network core, the electronicsystems processing and building the signals, the switching and data centres and, most of all,the transmitters and receivers.’ Three percent of the global energy demand goes into wirelesscommunication services. And with projections of the demand for mobile data to increasea hundred to ten thousand times over the next five to ten years, we are in trouble. ‘The problem
is that the communication industry in general has pretty much focused on trying to maximize
the number of bits that can be transmitted per second,’ McCune explains. ‘Very little attention
has been paid to the energy efficiency that goes along with that. I want to fix this.’

5G: a solution in the making
About Earl
On Wednesday 27 May 2020 ouresteemed colleague Earl McCune
has passed away. As of last year,
Earl was (part-time) professor
at the Electronic Circuits andArchitectures research groupat TU Delft and grew, in a shortperiod of time, to become anincredibly popular expert in thefield of sustainable wirelesscommunication systems. In oneof his last interviews (this article),
Earl told us that he was willing tofight a few persistent beliefs in the

Most of the hype in wireless communications focusses on
5G – the fifth-generation cellular network technology. ‘The
eventual switch to 5G comes with two major improvements,’
McCune explains. ‘One is the intended use of millimetre-wave
directed beams for communication, saving lots of energy. The
second improvement allows for a major increase in the speedof communications. This will enable, for example, internetof things controllable factories.’ The official goal of the 5G
communications standard is a ten thousand times increase indata traffic, at flat cost and flat energy use. ‘What they didn’t tellus, however, is how to exactly implement the standard and toachieve all this,’ McCune continues. ‘We know the math behind
5G, but it simply is not yet ready to be deployed on a massive
scale. In order to reach the 5G energy efficiency goal, all links inthe communication chain need to be overhauled.’

field of wireless communication.
Earl will not only be remembered
for his boundless enthusiasm
for the improvement of systems,

The official goal of the 5G communications standard
is a ten thousand times increase in data traffic

and the inexhaustible amount ofknowledge he brought with him;
more than that, Earl was a mentor,
an inspirer, an adventurer and awarm personality who put a smileon many people's faces with his
dry sense of Californian humour.

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‘In order to reach the 5G energy efficiency
goal, all links in the communication chain
need to be overhauled.’

The continuous effort to increase data rates has comewith a continuous decrease in energy efficiency. Goingfrom 2G to 4G, it has dropped from 60% to 20%‘Presently rolledout 5G networks
are about as energy
efficient as theold incandescentlightbulb.’

Power to the signal

Writing the textbook of next generation signal amplifiers

The present paradigm in wireless communications, laid down

There is a catch, though. ‘We need to build these square signals at communications-usefulin 1915, is to first build a very low-power signal. It consists oftransmit power levels, not in the microwatt range,’ McCune explains. ‘There is no textbook

the addition of many sinewaves, simultaneously carrying a few

explaining how to build a sampling system with high output power. We’re going to be writing

bytes of information. Next, this jumbled signal is amplified to athat.’ Being both a part-time professor at TU Delft and part-time consultant and entrepreneur incommunications useful power level of several watts. ‘There is

California, McCune is involved in two separate approaches to build these untraditional amplifiers.

something called Ohm’s law,’ McCune explains. ‘It says that if

In Silicon Valley, he pursues the idea of building one big switch, adjusting the power that is madeyou have certain signal properties, then you will not be efficientavailable to it. Here at TU Delft, the focus is placed on a new solution consisting of hundreds ofat amplifying these, particularly when you require linearity

smaller transistors, in varying sizes. ‘It’s like playing a very big organ, adding the power signals

in your circuitry.’ Linearity means that the high-level output

up to make the desired output,’ McCune explains. ‘For the lower range of 5G frequencies, this has

signal coming out of an amplifier is a faithful representation

to be below 6 GHz. But most of the unused 5G bandwidth is the millimetre wave bands, havingof the low-level input signal. To ensure linearity under all

frequencies above 24 GHz,’ McCune says. ‘We don’t yet have transistors with the capability thatcircumstances, the signal amplifiers will most of the timeeffectively can perform a switched operation at these operating frequencies, requiring transistor

operate well below their maximum output level.

speeds in excess of 600GHz, so we need to improve them by another threefold or more.’

As a consequence, the continuous effort to increase data rates has come with a continuous

No time to idle

decrease in energy efficiency. Going from 2G to 4G, the transmitter efficiency without any adjust­It’s not just the power supply for amplifying the wireless signals that has to be revisited.

ment of its topology has dropped from 60% to 20% when going from 2G to 4G signals. A twenty‘On average, when switched on, your desktop computer is not performing any useful tasks

percent efficiency means that for every watt of useful signal, four watts of energy will just end

for 96% of the time,’ says McCune. ‘Likewise, the components making up the digital core ofup as heat. ‘For 5G, the efficiency will be only 10%, meaning that nine watts will be turned into

the communications network – the switching and data centres – are idle about 72% of theheat,’ says McCune. ‘We’re paying for the power, we’re paying for the huge power supply, andtime. The logic components in the computer switch about a million times faster than the power

we’re paying to move that heat away into a giant block of aluminium serving as a heat sink.’ For

supplies presently used. To have immediate performance when needed, we just leave the power

presently rolled-out 5G using millimetre-waves, which is still based on 4G like technologies, theon.’ His proposed solution is quite like the modern cars that turn off and back on when waiting

efficiency is only a few percent. ‘That’s even worse than the old-fashioned incandescent lightat a traffic light. It takes so little time that it doesn’t interrupt your driving experience. ‘We canbulb,’ McCune continues. ‘The old tradition of using the linear amplifier, trying to find a version that

already build the power supplies that respond in less than one microsecond,’ McCune continues.

is efficient, has run its course. But, in our digital age, physics gives us another way to make an‘The problem is that the computing chip community has interleaved their computer logic circuitry

accurate signal. If you have a sampling-based system, using square signals, Ohm’s law then says

with some of the memory. Switch your computer off, and you’ll erase a part of its memory too.

you can be as efficient as you want it to be, bringing the efficiency of amplifiers up to 70%. That’s

We have to slightly rearchitect the chips, separating memory from logic. Then, we can reducea huge improvement, just by letting go of linearity and changing the circuitry. And we don’t have tocomputing power consumption by a factor of four, saving millions of euros.’

touch the signal standards themselves.’

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Line of sight communications
Probably the most hyped promise of 5G telecommunications is the use of directional beams
for communication, transmitting power only where you need it. The present 4G network relies onantenna’s that put out their radio signal across vast areas. As you move around campus, you’ll
always find the same signal everywhere. ‘From a transmitter point of view, that is silly,’ says
McCune. ‘This way, almost all radiated power is just going to warm up the grass. Using directed
power, the antenna will create small beams, sending radio waves of the same strength only towhere you are. When you move around, it will follow you like a theatre spotlight.’ It works a bit
like the satellite dishes used for satellite communications. But instead of parabolic antennas,
it takes the coordination of hundreds of small antennas to create a beam covering only a verysmall segment of the sky. ‘It is solved, but only in computer simulations,’ says McCune. ‘It willtake some years for it to work in real-time in the real world, especially for 5G in the millimetre
wave bands. The signal will be interrupted by bouncing off spinning windmills, cars driving by,
the buildings people enter and exit. Even you yourself are a reflector, as millimetre-waves cannot
penetrate the human skin.’‘There is no textbook explaining how to build a samplingsystem at power. We’re going to be writing that.’

The love for building things

overlapping. At just over a meter in diameter, it will hang in the middle of the

One evening, when McCune was twelve, his now late father explained a few months’ worth ofstadium. To handle the massive amount of wireless data, a bundle of optical

network theory of electrical circuits to him. ‘He was a good explainer, and it just made sense,’

fibres will connect the Fly’s Eye to the internet, much like your optic nerves aresays McCune. He now has more than 45 years of experience in technology development in

the communication highway between your eyes and your brain. ‘I just love thethe field of radiofrequency and wireless design, most of which he spent in industry. ‘I justeye metaphor,’ McCune says.

love to build things,’ he says, ‘and I have seen a lot of what works, and what doesn’t work.’
Enjoying an early retirement in California, but still wanting to help solve society's problems, he

Only a few minutes to dump satellite memory

accepted a professorship at TU Delft. ‘When pressured, industry will change its technology only

McCune was also intrigued by the communications problem posed by cubesats.

incrementally, just enough to keep making money. I thought we were missing something, there’s

These tiny satellites, consisting of up to a few ten-centimetre cubes, are cheap

so much room for big improvements.’

to build and to bring into earth orbit. They are often equipped with one or more

The Fly’s Eye project

Instead of having spots movingaround the stadium, the idea of the
Fly’s Eye is to ‘just make a lot ofspots,’ covering the entire stadium.

camera’s for earth observation, collecting huge amounts of data. At their altitudeof 500 kilometres they move so fast that direct line of sight communication‘Now here’s a challenge,’ McCune says. ‘Imagine the world cup soccer final with eighty thousandwith a ground station is severely limited. ‘We have only a few minutes tospectators who all, simultaneously, want to post their own high-resolution video of the winningtransmit gigabytes of data, and there are some very limiting constraints,’

goal. Can we do that?’ This is what the Fly’s Eye project is about, one of the ongoing TU Delft

McCune explains. ‘There isn’t much energy available in a ten-centimetre cube.

projects McCune is now involved in. ‘It is very multi-disciplinary, with Nuria Llombart-Juan from

The antenna can’t be very big either, limiting us to high radio frequencies. Then,the Terahertz Sensing group as the lead researcher,’ he says. ‘Instead of having spots moving

there’s the oxygen in earth’s atmosphere, which is very efficient at absorbing

around the stadium, the idea of the Fly’s Eye is to ‘just make a lot of spots,’ covering the entire

millimetre wave radiation.’ His voice sounds more and more enthusiastic

stadium. We simply hand the signal off to the next spot, should a user move around too much.’with every added challenge he mentions. ‘It’s a 5G type of problem,’ he says.

One of these passport-photo-sized spots is already being tested in the lab. It consists of a bunch‘It involves energy, antennas, all kinds of things. To boost efficiency from twoof transmitters covered by a clear plastic lens that is able to focus radio waves in the millimetre-

percent to fifty percent, we have to overhaul everything.’

wave spectrum. The eventual structure will have 1500 of these spots, their beams partially140

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141

Technology is constantly on the move. Applications now

22

Is sharing personal data amatter of all or nothing?
Text: Merijn van Nuland | Photography: Annelies van ’t Hulavailable were unthinkable in the past, from sensors in watches
that can count your steps to apps that help to improve yoursleeping pattern. This technology is used not only to collectdata for the user, but also to share this data with others.

Keeping track
GPS trackers are tiny transmitters, often concealed in a watch
which can, for example, be used to help parents track thelocation of their child. Very convenient, because it enables

New digital technology is making it increasingly easy to shareparents to keep an eye on what their child is up to. ‘The

personal data. This brings all sorts of benefits, but it can also

problem is that with current technology you often have tolead to loss of privacy and sense of responsibility. Birna vanintentions, but it also leads to all kinds of ethical concerns.

Riemsdijk, computer scientist at the Delft Data Science initiative

Constant surveillance by a parent may affect the privacy of theat TU Delft and former lecturer of the Intimate Computing

child and lead to a diminished sense of responsibility. After

master course, is looking for the golden mean.

142

share all the data at once. That might be done with the best

‘The problem isthat with current
technology you often
have to share all thedata at once. Thatmight be done withthe best intentions,but it also leads toall kinds of ethicalconcerns.’

all, it means there is always someone watching you who canintervene when necessary,’ says Van Riemsdijk.

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Flexible technology

About Birna

Psychiatric disorders

Van Riemsdijk is looking to find the golden

Birna van Riemsdijk is associate professor Intimate

Developing technology to share data in a more flexible

mean with her research. She wants to take

Computing at University of Twente. She is also guest

way also has important applications in other areas,full advantage of the latest technology while

researcher in the Interactive Intelligence section at TU

such as healthcare. Generating and sharing data

doing justice to the privacy and responsibility

Delft. Her research mission is to develop theory andcould facilitate the work of healthcare providers, whileof users. This will be done by making thesoftware for creating intimate technologies that takepatients can also use the technology to help manage

technology’s software more flexible. ‘Indeed,

into account our human vulnerability in supportinga disease or disorder. The University of Twente andhow exactly data should be handled depends

us in our daily lives: intimate computing is computing

Scelta (GGNet), an expertise centre for treating

greatly on context,’ says Van Riemsdijk. ‘For

with vulnerability. For her research she was awarded apersonality disorders, are conducting research into

example, you would probably like to keep

Vidi personal grant and the Dutch Prize for Research

the use of technology to treat people with a borderline

a closer eye on a child with behavioural

in ICT 2014. During this successful period she worked

personality disorder. There are indications that temper

problems. The thing is that each parent has

at the Faculty of EEMCS. ‘At the Interactive Intelligencetantrums and self-injury or suicidal behaviour are

his or her own view on how to raise a child.

section at TU Delft the human-centered focus of mypreceded by physical signals such as an elevated

There are wide differences among families,

work really started to take shape. Not only by inspiring

heart rate. Once such signals can be identified, it may

for instance, concerning the time of day

computational notions, or by studying how programmers

be possible to perform an intervention.

children need to be at home. We are therefore

use our created languages, but more and more throughaiming for technology that meets the norms

a focus on supportive technology: creating agents toTogether with Van Riemsdijk, research is being

and values of its users.’

support people in their daily lives, requiring collaboration

carried out into how this technology can be madebetween human and machine.’

more flexible with regard to data sharing between thetherapist and the patient, based on the technology
developed for GPS tracking. This too requires taking
into account the privacy and responsibility of users.

User freedom
Ultimately, Van Riemsdijk would like software andapp users to have greater control of how they share
their data, and with whom. ‘We have to realise that

Integrating agreements
However, current digital technology is not yet capable oftechnically representing and using the various agreements
made between users. This is going to change, if it is up to
Van Riemsdijk. She is working on technology which will

‘Children considered theflexible version of theapp more usable, andit gave them a greater
sense of friendship andindependence.’

not only enable users in the near future to represent theirmutual agreements on data sharing in the software, but will
also enable the software to interpret these agreements. For
example, the software could decide that agreements on safetyissues take precedence over conflicting appointments of lessimportance.

Developing such software is not straightforward.

functionality reflects the designer’s views on what it

It means giving users much more freedom to definemeans to be human. It is important that we, the users,

their data-sharing preferences. ‘Of course, all thoseare able to determine the way in which we want to use

additional options improve the technology, but they

an application. Sharing personal data should no longer

also add to its complexity. It is therefore important tobe a matter of all or nothing. We must strive to find afind out if users can still understand the technology.’

golden mean. It is therefore important that we develop

All in all, the initial field study was quite encouraging!

technology that supports this.’

Dr. Alex Kayal, one of Van Riemsdijk’s graduates
developed a new app for families for sharing location
data as part of the COMMIT/ project, which was
subsequently tested in an out-of-school day care
centre. It turned out that the children considered the‘We have to realise thattechnology is never valuefree.’144

technology is never value-free. Every new app or

flexible version of the app more usable, and it gavethem a greater sense of friendship and independence.

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145

Solar cells available atbargain prices, but still
the revolution stagnates

23

Text: Merijn van Nuland | Photography: Thierry SchutIn its Climate Agreement, the Dutch government aims to reduce CO2
emissions by as much as 49% compared to 1990-levels by the year 2030.
That’s a laudable aim, says solar energy Professor Arno Smets, but achieving
it will be a major challenge. ‘It’s difficult to estimate how much reduction in
CO2 emissions each measure will actually deliver.’Arno Smets clearly sees the Climate Agreement as a positive step forward.
He pays tribute to the fact that, with this agreement presented, the Dutch
government is accepting its responsibility in the global challenge of the
21st century. He is also gratified to see the same government take the first
far-reaching policy steps towards reducing the emission of greenhouse gases.
But there is still something troubling TU Delft’s solar energy professor. Will it
really be enough? ‘I fear not,’ says Smets. ‘The energy transition is an extremelycomplicated political, administrative, economic, social and technologicalchallenge for our society. Although some measures will definitely deliver better
results than anticipated, achieving other key targets will not prove so easy or
predictable in practice. That could quickly put the 49% reduction at risk.’

Mission Innovation Champion
In the spring of 2019, Arno Smets has been named as one of the first
Mission Innovation Champions. Mission Innovation Champions is a new
initiative to honour pioneers in the field of clean energy. The programme
is part of Mission Innovation, a coalition of countries that agreed toaccelerate their efforts in the field of energy innovation at the Paris
Climate Summit. Arno Smets was chosen because of the impact of his‘The energy
transition is anextremely complex
challenge for oursociety.’teaching and research on the energy transition. ‘Climate change is thegreatest threat to humanity. I believe we can develop sustainable energy
systems that allow us to live in harmony with the planet. But we alsoneed to change people’s mind-sets and educate the world,’ Smets says.

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Unreliable energy sources
In his own research on solar energy, Smets has seen renewable

About Arno

energy production develop at an unimaginable pace. The produc­

Arno Smets researches

tion and upscaling of solar panels is happening much faster thantechnologies to convert solar

everyone expects. Solar panels are being produced in Asia atenergy into usable energy, suchbargain prices, making them available for less affluent households

as electrical or chemical energy.

even in the Netherlands. And whereas the 2013 Energy Agreement

In 2009 he received a Vidi for

did not feature even a single section on solar energy, in the 2019his research into the use of

Climate Agreement it has developed into one of the key pillars inthin silicon films to increase

the fight to tackle the climate issue.

the efficiency of solar panels.
In 2016, he was the first-ever‘Despite this, I can still see huge obstacles that we will needwinner of the edX Prize forto surmount before solar energy can really become part of a

Exceptional Contributions insustainable energy supply,’ says Smets. ‘This is because windOnline Teaching and Learning. In

and solar energy are still relatively unreliable sources of energy.

2015 he was appointed Antoni

A coal-fired power station is adjustable: you increase its output

van Leeuwenhoek professor at

if you need more power. But with clean energy, you’re completely

TU Delft.

dependent on the wind and sun: when the wind drops and it’s
cloudy, production is too low to meet the demand for energy.’

Tesla powered by grey energy
Another problem is the fact that electricity is difficult to store.

SCAN!

Technically, it’s not yet really possible to store solar energy fromthe summer for the darker days of winter. This means we’re stilllargely dependent on grey energy for now, says Smets, which again
has serious repercussions for other sustainability measures. ‘Takeelectric driving, for example. With government subsidies, you cancertainly ensure that more Dutch people start driving electric carsin the short term, but what benefit will that have if all of the Teslasneed to be charged using electricity from coal-fired power stations?’
Finally, but equally importantly, the integration of large-scale solarparks could be delayed. A solar park is a collection of a large
number of solar panels that can quickly generate a lot of electricity

Arno Smets about the amount ofenergy Stephen Kiprotich, a Ugandan
long-distance runner, produces during
a marathon.

locally. Smets: ‘In recent years, the government has been generous
in offering subsidies for these parks, but the initiators struggle tofind other investors. Grid operators can sometimes find it difficult
to make the necessary expansions to the electricity network tokeep up. What’s more, we’ll face a real shortage of electricians to
install solar panels if this market continues to grow.’‘We are unawareof the complex world
behind the wall
socket.’148

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MOOC’s
Solar energy Professor Arno Smets has already reached hundredsof thousands of viewers with his MOOCS (Massive Open Online
Courses). He has even inspired his viewers to install their own solar
panels in places where there is poor electricity supply. Smets’ online
lectures are popular because of his lively style of presentation. But,of course, the topic also appeals to lots of viewers. ‘When we started,
no MOOC had been made about solar cells. We explain how solar
power works and explore the fundamental principle of photovoltaic (PV)energy conversion. How do you convert solar energy into electricity?
We demonstrate how the technology works and how you can build amodest system yourself. There’s a lot of interest in sustainability and thisappeals to lots of people.’

Take electric driving, for example. With
government subsidies, you can certainly ensurethat more Dutch people start driving electriccars in the short term, but what benefit will thathave if all of the Teslas need to be charged using
electricity from coal-fired power stations?

Integrated approach

Raising awareness

Smets’ basic message is that solar energy is currently not yet

However uncertain the solar revolution may be, solar panels area miracle cure. Existing scenarios may predict a key role forgood for one thing at least: raising awareness. ‘All of us want tosolar energy in the global energy transition, but all kinds ofuse electric devices and appliances, so we can use WhatsApp

conditions will first need to be met for that to be achieved.

and watch Netflix. But we are unaware of the complex world

According to Smets, the key is to pursue an integrated

behind the wall socket. How is electricity produced, what is

approach, because solar energy can only become a success

its impact on life on Earth and why isn’t it done completely

with a good electricity grid, better opportunities for storage,

sustainably? We don’t ask ourselves these questions often

sufficient investors and fitters, space for solar parks, social

enough. But if you have a few solar panels on the roof, thisacceptance, etc. The success of any solar revolution in theelectricity production suddenly becomes much more tangible:

Netherlands will depend on all of these factors. ‘Things could

you can actually reverse the dials in your meter cupboard!’‘How is electricity
produced, what is
its impact on life on
Earth and why isn’t
it done completely
sustainably?’

progress quickly or slowly, which makes it difficult to makeuseful predictions. Currently, we just don’t know how much CO2This helps consumers to understand the ethical issue that

reduction every euro you invest will deliver.’the energy transition really is. In that respect, the energy
sector is quite similar to other sectors of industry, such as

When he refers to an integrated approach, Smets means thatthe clothing industry. We like to buy cheap T-shirts, but never

all stakeholders take responsibility for achieving a smooth

wonder about the conditions in which they are manufactured.

energy transition. An example: the last two years have seen

And we certainly don’t want to see these poor conditions ina slight drop in worldwide investments in renewable energy.

our backyard, any more than we want to see wind turbines

This lack of investment could prove an obstacle for the energy

or large solar parks. But in a small and busy country like thetransition. ‘I recently checked and my own pension fund, forNetherlands, there’s no escaping the fact that the energy

example, invests only 1.3% of the budget in renewable energy.

transition will make visible changes to our surroundings, feels

That’s nowhere near enough to achieve all these projects.’

Smets. If we want to make the transition to renewable energy,
we need to be willing to make sacrifices.

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24

A post-coronavirus
society
Text: Dave Boomkens | Photography: Marcel Krijger

The COVID-19 pandemic is not only putting society to the test, but also
science. Scientists who have been able to spend their lives working quietly inthe background suddenly find themselves the centre of attention. One suchresearcher is Piet Van Mieghem, a professor at TU Delft. He usually researches
all kinds of complex networks that describe interactions. For example theinternet or a more complex topic like the brain. But since March of this year,
Van Mieghem has been using his knowledge as a weapon against COVID-19.
At the request of the RIVM (National Institute for Public Health and theEnvironment), and with the help of three PhD students, he tries to predict thecourse of the virus and is working on a so-called exit strategy.

It was exactly ten years ago that Piet Van Mieghem

are known, then the the spread of an epidemic canbegan to investigate digital viruses that sneak into ourbe computed. In particular, if the correct COVID-19

networks via emails or system faults, with undesirable

parameters and an accurate transmission map of theconsequences. Now that we are experiencing theNetherlands were available, then we could determine

deadliest pandemic since the Spanish flu, Van Mieghem

the infection chance in any region.

is shifting his focus from a digital to a biologicalvirus. ‘Because,’ says Van Mieghem, ‘the undelying

You can calculate how many people are being infected

mathematical models are basically the same.’

per municipality or province. With NIPA we are doing

NIPA

exactly the same, but in reverse as we don’t know the
precise parameters associated with COVID-19. So

With this in mind, Van Mieghem and his colleagues

instead, we are recording the number of infections per

are applying their special algorithm, NIPA*, to themunicipality per unit of time. The more frequently welatest data supplied by the RIVM. They hope that NIPA

sample the number of infected individuals, the more

will enable them to chart the progress of COVID-19.

accurately we can determine the parameters for an epi-

‘Epidemic models on any network rely on both virus

demic model. Once we have recorded time series longspecific parameters and the underlying contact graph,enough, NIPA returns accurate enough parameters toover which the virus propagates. If these parameters

predict the near future, i.e. a couple of days in advance.’*NIPA =
Network-Inference-based Prediction
Algorithm

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153‘Once we have recorded enough time series,
we can start making simulations and models.
So we are trying to look one, two, three oreven four days ahead.’

Human brain

for destroying a network? And in this case we are also

NIPA brings various academic disciplines together.

reversing things. The coronavirus crisis has degraded

One of these is network science, a relatively new

our society to a certain extent. What steps will we

discipline that studies the functions of a complex

need to take together in order to return to some kind

network and its associated underlying structure. Weof normality soon? We call this recoverability. The

can use this discipline to study critical infrastructures,

Dutch government has imposed all kinds of measures

such as the internet and power grids, but also to study

concerning the coronavirus, but these cannot all be

epidemics, or the human brain. Questions you may try

lifted at once as there are plenty of scenarios possible

to answer – when it comes to the brain – include: what

in which the virus could start to spread again.’

are the topological properties of such a brain-activity
network? How does the structure of the brain change

Financial contribution

with age? Can you determine whether someone is

But that is still some way off. For the time being, Van

intelligent (or has a high IQ) from their network?

Mieghem and his colleagues will be continuing to work

Exit strategy

overtime. In order to support Van Mieghem and all theother researchers at TU Delft who are working round

Back to COVID-19. Van Mieghem is also busy trying

the clock to combat COVID-19, we have set up theto propose and assess exit strategies. Together

TU Delft COVID-19 Response Fund. The fund is being

with a number of fellow professors, Van Mieghem

used to provide rapid financial support to researchers

is part of a team put together by RIVM to combat

and students, ensuring no valuable time is wasted.

the coronavirus. For the time being, Piet also gets
help from a PhD student who recently defended his
doctorate, but is unable to return to China because of
the coronavirus crisis. ‘Since he has nowhere else togo, he is keen to do something useful and help us withthis exit strategy,’ explains Van Mieghem. ‘For us this isactually a piece of cake, as we have carried out a gooddeal of research in recent years into the effects ofearthquakes, floods and terrorist attacks on a network.
This kind of thing puts a network under pressure, so
it doesn’t function perfectly everywhere. Questions
we examined in recent years include How quickly can
you degrade a network? and What is the best strategy

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25

Improving theeffectiveness of speech
recognition‘Siri, find the quickest route home.’ An instruction like that given in a quiet room
is no problem at all for Apple’s virtual assistant, used on mobile phones andtablets. But if you ask the same question in a busy restaurant or with a strong
regional accent, Siri will find it slightly more difficult to understand what you
said. This is not pure chance. Speech recognition software currently only works
effectively if the person talking to it can be clearly understood, has reasonably
standard pronunciation and there is little background noise. If not, we hit thelimits of current technology, not only in the case of Siri, but also Google or

Text: Robert Visscher | Photography: Mark Prins and Dave Boomkens

How can you ensure that a computer understands exactly

Amazon, for example, who use similar software.
‘Currently, speech recognition has little to offer to people with speech
impediments, the elderly or someone who cannot speak clearly because of anwhat someone is saying even if they cannot speak theillness. These are the people who could benefit most from it, for communicating

language perfectly? In her quest to make this possible, Odettewith friends and family or controlling appliances and devices, for instance,’ says

Scharenborg is researching automatic speech recognition.

‘I actually knew
nothing about
speech, but at thevery first lecture,
I knew I was in theright place.’

Odette Scharenborg. As associate professor in TU Delft’s Faculty of EEMCS,
she is researching automatic speech recognition, exploring how you can teacha computer to recognise languages more effectively.

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Psychology of language
The current technology works thanks to a huge body of data that is used to train speech
recognition systems. The body of data is made up of two parts: speech and the textual
description (verbatim) of what was said (the transcription). Recordings are made of the speechof people having conversations, reading texts aloud, speaking to a robot or computer or giving
an interview or a lecture. All of these hours of audio material are written down and an indication
is given of where there is background noise or where noises occur made by the speaker, such as
laughing or licking their lips. But this system falls short. It is simply impossible (in terms of time,money and effort) to collect and transcribe enough data for all languages and all accents. Partly
because of this, the focus has been on collecting data from the ‘average person,’ which meansthat the elderly and children are not properly represented. People with speech impediments canalso find it difficult and tiring to speak into a machine over long periods. Equally, something saidby someone with a foreign accent will often not be properly recognised because of a lack oftraining data.

There are also some unwritten languages
that are still spoken widely. ‘Take the Mbosi

About Odettelanguage in sub-Saharan Africa, for example,

As associate professor in TU

a language spoken by around 110,000 people.

Delft’s Faculty of EEMCS, Odette

For the existing speech recognition systems,

Scharenborg is researching

there is simply not enough training material

automatic speech recognition,

available for that language. In addition,

exploring how you can teach a

the main problem is that training a speechcomputer to recognise languages

recognition system not only calls for the

more effectively.

speech data, but also a textual transcriptionof what was said. Of course, you can record alot, but quite aside from the fact that it takes
a lot of time and costs money, transcribing
what was said is not possible in an unwritten
language,’ says Scharenborg.

In her current research, Scharenborg
is combining insights frompsycholinguistics with the technologyof automatic speech recognition anddeep learning.

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159

Foto: Herman Verheij

On the ground floor of building 28 (Mathematics &Computer Science) there is a cabin that is about the size ofa garden shed. In this cabin Odette Scharenborg’s listening
experiments take place.

Whenever we learn a new language, we create new phonetic categories. For
example, when a Dutch person learns the English word the. This is different
from the familiar Dutch de or te or the a in bad or bat mentioned earlier. The
researchers aim to teach the computer this process of creating a new phonetic
category. In the future, this should enable speech recognition to teach itself to

Is it possible to develop a new form ofspeech recognition that does not use textual
transcriptions, bringing an end to the exclusionof certain groups? This is what Scharenborg
is currently researching. She is taking afundamental look at automatic speech
recognition. This involves such issues as how
you recognise and categorise sounds. She isalso exploring the psycholinguistic side, thepsychology of language.

New phonetic categories
In one of the methods Scharenborg is
researching, she is looking at the sounds oflanguages and how they differ and what theylearn languages in this way and recognise pronunciation, even if it deviates fromthe average.

Safe door
The approach is based on experiments that Scharenborg conducted with humanlisteners. Test subjects listened to sounds or headphones. ‘L and r are two
separate phonetic categories, but you can also mix them artificially. The soundyou then pronounce sounds just as much like an r as an l. We gave test subjects
words that ended with the letter that sounds something like a cross between r
and l. If you give them the word peper/l, they interpret the sound as a r, because
it makes peper, which is actually a real Dutch word (pepper). After that, the test
subjects start classing it as an r. The opposite happens if the same sound isgiven in the word taker/l, when people will interpret the same ambiguous soundas l, because takel is a Dutch word and taker isn’t. You actually retune it in yourhead.’

have in common. Every language has its own
set of sound classes, or phonetic categories,
and associated pronunciation. Take thepronunciation of bed, bet, bat or bad in English.
‘If a Dutch person pronounces these words,‘The current technology works thanks to a huge bodyof data that is used to train speech recognition systems.’

they will sound the same to many people. But
that’s not the case for an English person, forwhom these are four different words with four
different pronunciations,’ says Scharenborg.
So even in languages like Dutch and English,
which have a lot of overlap, there are different

In her current research,
Scharenborg is combining
insights from psycholinguistics
with the technology of automatic
speech recognition and deeplearning.

sounds (the vowel in bed and bad) and thesame sound is sometimes pronounced
differently (the d and t at the end of theword sound the same in Dutch but different
in English). ‘When developing a speech
recognition system for an unwritten language,
you can take advantage of the things that
languages have in common. For example, theDutch e sounds approximately like the Englishe, but the a in bat sounds something like a

For these listening experiments, test subjects sit in a room that has been
specially developed. On the ground floor of the Mathematics & Computer
Science building, Scharenborg points to a cabin, roughly the size of a garden
shed. She opens the heavy, wide door. It is so thick that it looks like a safe
door. ‘It’s in here that we do the experiments. There’s no distraction from othersounds. Can you feel the pressure on your ears? That’s because the room is
low-noise,’ says Scharenborg.
In the cabin, there is a chair and a desk. On that, there are headphones anda computer. On the screen, test subjects can read words and they can hearsounds via the headphones. There is also a window. This ensures that thetesters always have contact with a supervisor who can see if everything is
working as it should.

cross between the Dutch a and e. You can usethat knowledge to train a model of the English
a based on a model for the Dutch e,’ explains
Scharenborg.

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The current technology works thanks
to a huge body of data that is used totrain speech recognition systems.

The data that the scientists collect in the test is being used to make a new model that should
ultimately result in better speech recognition. In it, the model itself judges whether or not a newphonetic category is needed and you no longer have to enter it. This is a major step forward forautomatic speech recognition. The model was inspired by our brain and our deep neurologicalsystem, says Scharenborg. It is known as a deep neural network. ‘We are the first to investigate
self-learning speech recognition systems and we are currently working with a colleague in the
United States to develop technology for this. I expect to see the first results within two years.’

Bridging the divide between humanities and sciences
Will this soon produce an effective system that can rival Siri?
We cannot really expect that any time soon. The technology is
still in its very early days. Scharenborg’s research is primarily
fundamental in nature. Despite that, it is laying the foundations‘Everyone knowsthat it’s harder tounderstand someone
you are talking to
if there’s a lot ofbackground noise.’162

for a new type of automatic speech recognition. A program that

The academics working in the two different fields

Even at secondary school, Scharenborg was goodworks perfectly is still a distant prospect.

often don’t even know each other. This is somethingat both humanities and science subjects. ‘I wasthat Scharenborg aims to change. For years, she

unsure about what to study, which is why I chose

In a previous NWO Vidi research project, Scharenborg also

has been organising the largest conference on thea programme focusing on language, speech andexplored speech recognition. ‘Everyone knows that it’s harder tosubject of speech recognition, bringing together bothcomputer science at Radboud University. I actually

understand someone you are talking to if there’s a lot of back-communities. ‘Both groups still focus too much on

knew nothing about speech, but at the very first lecture,ground noise. It becomes even more difficult if someone isn’t

their own field. For applied scientists working on

I knew I was in the right place. Almost everyone talks

speaking their native language, but another language because

deep learning, speech is a type of data that they use

to each other and a lot of communication is done

they want to order something to drink in a busy café on holiday.

to develop technology. However, psycholinguistic

through speech. You can look at it from a physics

But why is it so much more difficult to understand each otherresearchers often have relatively little knowledge ofperspective by focusing on waves that propagate

when there’s background noise? And why is this more difficult

computers. In my view, these fields complement andspeech, but also explore how people recognise it.

in a foreign language than in your native tongue? I was keen to

can learn from each other, in terms of knowledge about

Being able to approach it from different sides reallyfind that out and ended up learning more about how humans

both speech and computer systems. I want them toappealed to me.’recognise speech.’engage in discussion.’

In her current research, Scharenborg is combining insights from

Knight Rider

psycholinguistics with the technology of automatic speech

Scharenborg has extensive experience of both

Knight Rider. In it, David Hasselhoff played the herorecognition and deep learning. Normally, these are separate

automatic speech recognition and deep learning

Michael Knight, who could speak to his car KITT. This

fields. Psycholinguistics is mainly the preserve of scientists

and therefore aims to bridge the divide. Before

supercar not only understood what was said, but also

and social scientists and focuses on language and speech andjoining TU Delft, she was associate professor in thetalked back and was intelligent. Knight and KITT also

how our brains recognise words. Speech recognition and deep

Linguistics department at Radboud University. ‘Myused a wrist watch to communicate when they werelearning are about technology and how you can use it to makeown field is speech recognition, but I also work withapart. Even then, I found it really interesting and thata self-learning system.

psycholinguistics. It makes logical sense for me to do

fascination has never gone away – I’m still working

my research at TU Delft now, because the technicalwith speech and technology.’‘In order to make further progress, we need to combine bothexpertise is here and research is conducted acrossfields. It seems rather strange to me that there are not moredisciplines. That’s why I don’t feel like an outsider, evenpeople who combine them. The aim of the people and thethough I’m virtually the only person in the world doingmachines is the same: to recognise words,’ says Scharenborg.

this research.’

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Without actually realising it, she was already working
with speech. ‘For example, I really loved the TV series

163

Diagnosing tuberculosis
with algorithms

26

Text: Koen Scheerders | Photography: Mark Prins

We’ve been able to decipher DNA for decades now. Until
recently, however, the information behind this blueprint of life
was inaccessible. Now mathematical algorithms unlock thisinformation for us. And that has highly promising applications,such as diagnosing complex tuberculosis infections.

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The abstract world of mathematics is far removed from a bed in a hospital in athan we thought. Each strain of bacteria has its own resistancedeveloping country. Take, for instance, the Church of Scotland Hospital in Tugela

profile. And a combination of strains can lead to a resistanceFerry, a small country town in South Africa. The hospital was unknown to thethat we are no longer able to treat.’ Such as the XDR-TB

rest of the world until it experienced an outbreak of tuberculosis, a contagious

infection that startled South Africa. Since then, 10 to 30 per

bacterial disease, in 2006. This extensively drug-resistant tuberculosis (XDR-

cent of TB infections are classified as complex.

TB) proved very difficult to treat and spelt death for most of the patients in thehospital. In almost no time, more than 300 patients with an XDR-TB infection

Resistance patterns

were reported throughout South Africa. For lack of proper treatment, theUsing patients’ genetic data, the algorithms that Abeel has

majority of these patients died.

come up with can pull apart such a complex infection at

Stubborn‘The idea is sequencing for anybody, anywhere.
Combined with our algorithms, this gives us atest that tells us it’s time to see a doctor.’

genetic level and derive which kinds of TB the patient has inhis body. Abeel: ‘An algorithm is a kind of computer program

Now, more than ten years later, thisthat is based on a model. Like the principle that a sequenceextensively drug-resistant family ofof DNA is a combination of DNA from multiple sources. We

TB bacteria is still responsible for a

can turn that into computer code. That enables us to divide thequarter of all XDR-TB cases in thesequence of tuberculosis DNA and find out what the original

area round Tugela Ferry. The strain

TB strains were.’ And that is greatly needed, because thehas become an example of the major

number of patients with complex TB infections continues

problem that resistance to TB anti­

to rise. Abeel: ‘The biggest problem is that 99 per cent of

biotics presents in developing countries in Africa. Nearly everyone there carries

the infections occur in developing countries. Those are thethis bacterial infection, which is easily spread from person to person through thecountries with the greatest resistance to antibiotics, but they

air. If a patient goes to hospital for treatment with antibiotics, the doctor cannot

are also the countries with limited funds for diagnosis andsee what form of TB the person has. Treatment is therefore completely effective

therapy.’‘Each strain ofbacteria has its own
resistance profile.
And a combinationof strains can lead toa resistance that weare no longer able totreat’

in only 20 per cent of all cases: the person is often prescribed either too much,or not enough, antibiotics. This inadequate treatment can lead to resistance: TB
strains that ‘get used’ to drugs and for which increasingly specific antibiotics areneeded. This can lead to an infection that is increasingly difficult to control, suchas with MDR-TB, which can easily spread within South Africa and beyond.

Complex infections
In Delft, Thomas Abeel is working on a solution to this global problem. Together
with partners, such as hospitals in South Africa, he diagnoses cases including
complex TB infections, which consist of multiple types of TB bacteria. But
instead of a blood test or X-rays, he is using algorithms. ‘Complex infections are
therefore more difficult to treat, which increases the risk of contagion,’ Abeel
explains. ‘One of our findings is that there are many more complex infections

Thomas Abeel's algorithms reveal resistance patterns in
TB strains and create prospects for new treatment options.

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‘There’s no reason to assume that we cannot apply ouralgorithms in other fields.’

Chemotherapy

Technology

Thomas Abeel’s algorithms reveal resistance patterns

Nevertheless, Abeel says we may still have to wait

in TB strains and create prospects for new treatment

a long time before complex TB patients can be

options. It takes more than just a couple of weeks

treated individually. One of the reasons lies in theto treat someone for TB; it is a long and arduous

technological challenges. For instance, how do you

treatment. Abeel: ‘People often take four kinds ofobtain genetic material in a developing country?

antibiotics for two months, followed by two kinds

Abeel: ‘We have all the components, but it will still takefor another four months. For an MDR-TB infection,

several years of technological development before

the regime lasts two years and is often much more

everything can really all be used together.’ One of thecomplex. The drugs have serious side effects, such as

most promising developments in this area is nanopore

skin discolouration and disorientation. It’s almost likesequencing: unravelling patients’ DNA with a small

chemotherapy.’ Many patients often feel much better

device that looks like a USB stick that fits in your laptop

after a week and therefore stop that arduous treatment

computer. The company that is developing this is also

too early. And that breeds even more resistance. Abeel:working on a DNA pen that extracts DNA directly from‘If we know exactly which antibiotics still work for eachblood or saliva. The rear of the extraction pen emitsstrain, we can diagnose and treat complex TB patientsa drop of prepared material that is fully suitable formore precisely.’ That increases the chance of being

nanopore sequencing. Abeel: ‘The idea is ‘sequencing

cured immensely.

for anybody, anywhere’. Combined with our algorithms,
this technology gives us a test that tells us: yes, youhave TB; time to see a doctor. Or that a doctor can use
it to make a diagnosis and a suitable treatment plan.’

About ThomasThomas Abeel studied Computer
Science Engineering in Ghent. After
graduation, he took a PhD in Plant
Biotechnology, followed by a threeyear internship at the Broad Institutein Boston, part of the Massachusetts
Institute of Technology (MIT). It wasthere that he started his work on
the genetic analysis of tuberculosis.
Since 2014, he has been recently
promoted to associate professor

Application
But it doesn’t stop there, Abeel thinks. His algorithms
can be used in an even broader context, such as byapplying them to the food industry. ‘Maybe we want
to be able to check the chicken in the supermarket
for resistant bacteria? Or food producers might want
to check their yoghurt cultures or strains of yeast forcontamination? DNA sequences form the basis, so
there is no reason whatsoever to assume that thesealgorithms cannot be used elsewhere. That, too, isdiagnostics.’of Bioinformatics in the Intelligent
Systems Department of theFaculty of Electrical Engineering,
Mathematics and Computer Science
at TU Delft. He still holds his guest
appointment at the Broad Institute.

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27

Tackling tumours using
mathematics
Text: Dave Boomkens | Photography: Mark Prins

Marleen Keijzer
Marleen, what first sparked your interest in mathematics
within radiotherapy?
In the mid-1980s, I attended a conference in America on how laser light is used
for medical applications. For example, in the case of atherosclerosis, how doRadiotherapy is one of the treatments for cancer, but designing atreatment plan is a challenging task. What is the best way to distributetreat a particular type of cancer? At the time, this was all relatively uncharted
research territory. Soon after, I moved from Delft to the United States in orderthe unavoidable high doses to healthy surrounding tissue, as to avoid

to apply a Monte Carlo method – in other words mathematics – to simulate

complications? Mathematical models have an important role to play inlight scattering. I wrote articles and worked with various hospitals, but decided

ensuring that radiotherapy can be conducted with minimal impact on theto return in 1989. Back in the Netherlands, I completed my PhD thesis on
calculating light propagation in tissue. If you put a flashlight against your cheek,

patient's quality of life. Marleen Keijzer (lecturer at the Delft Institute of

most of your face will turn red. That is scattered light. But how does the light

Applied Mathematics) and her former EEMCS student Sebastiaan Breedveld

actually get there? After my PhD, I worked on several more research projects, but(assistant professor at Erasmus MC) discuss the role of mathematics in anever-changing field: radiotherapy.

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you deal with a constricted blood vessel? And how could lasers be used to‘If you put aflashlight against
your cheek, mostof your face willturn red. That is
scattered light.
But how does thelight actually getthere?’

soon realised that I much preferred teaching and supervising students with theirgraduation research. For the latter, the focus was actually always on the useful
application of mathematics, for example within radiotherapy.

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Final-year students and radiotherapy. What challenges lay ahead of them?
In the field of radiotherapy, it was still possible to make major strides. Graduating students
were given all the space needed to design and program their own optimisation methods. An
optimised plan of this kind gives you the maximum opportunity to control the tumour andminimise the risk of damage to healthy tissue. So you search for the desired dose distribution
and use optimisation to determine how the beams (incidence directions from which the patient isirradiated) should relate to each other. What happens if you administer one beam here? And whatconsequences will that have for the dose applied there? Not so long ago, this still had to be done
manually: a radiotherapy technician set the beams, an advanced computer program calculated
the dose distribution and the radiotherapy technician then adjusted the beams to achieve theoptimum dose distribution. The problem with radiotherapy is that it doesn’t just involve one
single criterion, but numerous conflicting criteria. Optimising a radiotherapy plan could therefore
easily take up a whole day.

Sebastiaan Breedveld was one of yourgraduating students. What exactly did
he do?
I supervised Sebastiaan for a while, but heeventually did his PhD research at Erasmus
MC – Daniel den Hoed. He was awarded his
PhD cum laude on the subject of optimisation.
Because radiotherapy technicians were having
to devote a whole day to a radiotherapy
plan, Sebastiaan developed a method inwhich optimisation was fully managed by acomputer. An important component of this is
the so-called wish list. For some organs, theradiation tolerances are well known. You’redealing with strict limits. It’s important totake account of these limits, because if theradiation dose is too high, for example in thecase of spinal treatment, it may leave thepatient paralysed. But the reverse is also true:
if you radiate a tumour using less than theminimum dose, it may start to grow back. As
well as adhering to strict limits, you need tokeep the dose administered to each organ
as low as possible. The wish list allows you
to do this in a prioritised way (one by one). In
order to guarantee quality of life, one organ
is sometimes more important than the other.
This is something you will also take accountof when developing a treatment plan.

About Marleen and Sebastiaan
Marleen Keijzer is a lecturer at the Delft Instituteof Applied Mathematics, also known as DIAM, at
TU Delft. As part of her job, Keijzer is responsible forthe first-year course in Mathematical Modelling, andteaching and coaching students is what she enjoys
most. In the last decades, Marleen has supervised
numerous students during their graduation projects
or PhD programmes. Most of her projects werebased at the Daniel den Hoed Clinic – now Erasmus
MC – and focussed on radiotherapy treatment
planning. Together with her colleague Theresia van
Essen, Marleen is currently setting up an online
course In Hands-on Optimisation. Keijzer also
recently became vice-chair of the TU Delft Works
Council.
Sebastiaan Breedveld studied Applied Mathematics
at TU Delft. Both his Master’s and PhD research
focused on the automation of treatment plans withinradiotherapy. Breedveld is an assistant professor at
Erasmus MC, where he is continuing his research
aimed at improving radiotherapy treatment methods.

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Pictured is a radiotherapy treatment unit. The extension
at the top-left can rotate around the patient, and deliver
beams of ionising radiation. By rotating to a different
position, the patient is irradiated by another ‘beam’
direction. The number of beam directions, their directions,and the intensity distribution within each beam are degrees
of freedom which allow the delivery of complex dose
distributions inside the patient. Obtaining optimal settings
is our challenge, and we use mathematical optimisation to
obtain them.

‘In radiotherapy, together witheach problem solved, a basis iscreated for new opportunities
to further enhance treatment!’

Sebastiaan Breedveld
Sebastiaan, what first sparked your interest inmathematics within radiotherapy?
I was always eager to do something in the world of medicine.
Eventually I opted for a study in Applied Mathematics at TU Delft.
But I kept being attracted by the medical field. With that attraction
in mind, I decided to do my graduation research on a mathematicalissue with a medical application. Because Marleen lectures on
the subject, I thought: ‘I would like her to supervise my graduation
research!’ Via Marleen, I ended up at Erasmus MC – Daniel den
Hoed in Rotterdam.

So this radiation issue is really about
optimisation…

it all in a model. This is a very useful application for

How did you manage to combine mathematics andradiotherapy there?

mathematics, because as soon as you realise where

Maybe I should tell you something about radiotherapy first.

Yes, that’s actually what it comes down to. After all,the uncertainties are, you can start taking them into

Radiotherapy is used in approximately half of all diagnosed

numerous optimisation methods are being usedaccount. It is a very practical EEMCS issue.

cases of cancer. Radiotherapy is all about irradiating tumoursin radiotherapy. Nowadays, the maths are done by– you’re actually destroying cells. To do that effectively, you needcomputers. But it still takes time. The graduation

What challenges are there for the future?

students I am now supervising are working toRadiotherapy techniques could be customised more. In

settings for the radiotherapy device that will result in the desired

make this process faster and more practical whilethe 1960s, they would put a piece of lead on a patient,dose distribution. What makes it problematic is that you’realso tailoring it more effectively to the individualwith an opening cut out for the radiation beam at thedealing with ionising beams that go straight through a patient.

patient. Ideally, you want to fine-tune the plan whenlevel of the tumour. This meant that the radiation beam

Such a beam actually damages everything in its path. On thethe patient is actually lying on the treatment couch

was limited to the tumour alone. Today, everything is

one hand, you of course want to apply enough radiation to beof the radiotherapy device. Real time. The humandone using three-dimensional CT scans, fast computerable to eliminate the tumour. But then again, you don’t want tobody is always moving, while a radiotherapy plan is

calculations and highly targeted radiation beams.

do this at the expense of the surrounding organs: your aim is tomade weeks before the start of the first treatment.

There has been significant progress, but treatment

minimise the risk of complications as much as possible. Take a

If the bladder is slightly fuller, it may have pushed an

could still be tailored more effectively to the individual

tumour in the head and neck area. If you expose the small salivaryorgan or tumour into a slightly different position, forpatient. Also, planning methods are still not anything

glands to a dose above its tolerance during irradiation, this may

example. With that issue in mind, we had anotherbut standard. It would be great if planning methods

result in permanent damage. It may lead to a situation where thedoctoral candidate develop a statistical model of thewere generally accepted and made easily accessible,

patient has to drink a little water every 30 minutes, even at night.

movements of the prostate. He analysed numerous

so their use would not be limited to the university

What dose do you opt for? And how do you then distribute thatCT scans from different patients, identified the most

hospitals of wealthy countries.

dose? These are important questions that involve mathematicala radiotherapy treatment plan. This plan actually describes theimportant movements from these and summarised

calculations.

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Radiation therapy is one of the mostimportant treatments against cancer.
One of the ways to do this is throughexternal beam radiotherapy (EBRT).
A Linac (a linear particle accelerator)
is often used for this treatment. The
position of the angles is one of the
problems you have to deal with during
the preparation of the treatment. In
other words: from which directions
the patient is going to be irradiated.
As you can see in the video, there aredifferent degrees of freedom that canbe used and combined. The device
in the video is used in the majority of
the hospitals. For both traditional andmore contemporary treatments, thinkof proton therapy.

SCAN!

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How did you include these questions in your own research?
It’s worth knowing that my research involved two stages. The first stage

In the years ahead, what will be the greatest challenge
in the field of radiotherapy?

was to investigate how the available equipment could be used as effectively

The HollandPTC outpatient centre – based on the TU Delftas possible. In the Netherlands, we’ve seen a rapid development of most

campus – recently started treating patients using proton

equipment, while the range of possible applications has lagged behind. Smarttherapy. This form of radiotherapy for cancer is new to theuse of mathematical models enabled us to catch up and put the available

Netherlands. Protons are small, positively charged atomic

equipment to maximum use. The second step was to answer the question: how

particles that enable high-precision irradiation. This means

do you distribute the dose? In order to find out, I asked a number of colleagues:that less radiation is delivered to healthy tissues, thus reduces

what is it you would like to see in a therapy plan? Based on that input, I compiled

the risk of side-effects. TU Delft is working on the technicala wish list: a list that I could use to guide the optimisation. Running through thisside of this study. Rotterdam and Leiden manage the medical

wish list, you can work towards a radiation dose that is highly precise based onside. But there’s another question: how can you generate thesophisticated calculations. At that time, the process was relatively new.

radiotherapy treatment plan even faster and more effective?

‘The problem withradiotherapy is thatit doesn’t just involve
one single criterion,
but numerous
conflicting criteria.’

Imagine you need to make last-minute changes to a plan. How
then do you ensure you can go through all those gigabytes ofactive data in just a few seconds?

‘For some organs, it’s perfectly clear how highthe radiation dose can still be.You’re dealing withstrict limits.’

Would you ever change the world of radiotherapy for another one?
When I started here, I thought: when I’ve done my bit, I’ll slip away and move into hydraulicengineering. I’ve now passed that point. What makes radiotherapy interesting is that newtechniques are continually emerging. For example, proton therapy has been around fora decade, but at Holland PTC, the very first patient was only treated December 2018.
In radiotherapy, together with each problem solved, a basis is created for new opportunities

How did you apply the wish list in practice?

to further enhance treatment!

This wish list ultimately generated automated working methods. Now, there
were two plans: one plan that had been developed clinically and one plan
generated automatically. In order to find out which method worked best, botha clinical and an automatically generated plan were developed for 50 patients.
By doing this, we hoped to achieve some kind of statistical relevance. Bothvariants were submitted to the treating physician who was then asked: whichplan would you use to treat this patient? The doctor had not been told which
variant had been calculated manually or automatically. After repeating this33 times, we ended the experiment. We found that in 32 out of 33 cases, thepreference was for – what turned out to be – the automatically generated plan.
The difference in quality was so convincing that from an ethical perspective wefelt compelled to make an effort to treat all patients within this group in the newway. In other words, the wish list worked.

What makes radiotherapy interesting is that new techniques are continually emerging. For example,
proton therapy has been around for a decade, but at Holland PTC, the very first patient was only
treated December 2018. In radiotherapy, together with each problem solved, a basis is created for
new opportunities to further enhance treatment!

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Ultrasound from a plaster
Text: Koen Scheerders | Photo: Mark Prins

28

Ultrasound scanning via a plaster or catheter: Michiel Pertijs
sees real possibilities for reducing the size of ultrasoundequipment to millimetre format. And it’s all thanks to smart chiptechnology.

Your very first photograph as a baby was probably an ultra-‘Our collaborative
partnerships enable us
to make more progress
towards a medical
application. I find that
extremely motivating.’sound image. A black and white picture on which, with a little
imagination, you can recognise a baby in the womb. Ultrasoundscanning is a cost-effective and safe imaging method forviewing inside the body. It is not only suitable for pictures of
the unborn child, but for all kinds of organs, as long as they are
made of soft tissue.
There are good reasons why doctors have long dreamt ofprobes that are so small that they can enable real-time imaging during minimally-invasive surgery, such as an angioplastyor the replacement of a heart valve. Or how about a wirelessincontinence plaster that monitors bladder volume and sets
off an alarm when it’s time to urinate? All of this is achievable
within the foreseeable future – in around 5 to 10 years, if you
ask Michiel Pertijs.

Miniaturisation
Together with its TU Delft partners, Michiel Pertijs’ research group is working on the‘miniaturisation’ of ultrasound scanning. This is because the technology needs to become
considerably smaller before a doctor can fit a patient with an ultrasound catheter. Pertijs: ‘For
ultrasound scanning, you need a probe with thousands of transducers that transmit and receive
ultrasound. Currently, this kind of probe is connected by a thick cable to a box next to the bed.
This is packed with electronics: a piece of electronics to transmit and receive signals for every
single element. However, passing thousands of cables through a catheter of 3 mm in diameteris simply impossible.’

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179‘Pertijs believes that he can make the chips even smarter.
He is working on chips that digitise the ultrasoundsignals first, potentially making the flow of informationeven more efficient.’

Chip technology
The challenge facing Pertijs and his research group is to miniaturise thefunctionality of this large box of electronics and make the connection between
the probe and the monitor as efficient as possible. Chip technology plays a rolein this. ‘We can use it to make smart switches at micrometre level,’ explains
Pertijs. ‘Small enough to be able to control those thousands of transducers fromthe probe.’ Thanks to smart switches, his chips can already process some of thesignals before they are sent through the cables. ‘If you can already combine thesignals of groups of elements on the chip, you only need to transmit the sumof those signals rather than the signals from all those individual elements.
This alone reduces the number of cables by a factor of 10.’

Digitisation
Pertijs believes that he can make the chips
even smarter. He is working on chips

About Michiel
Michiel Pertijs is associate
professor in the Electronic
Instrumentation Lab in TU Delft’s
Microelectronics department.
He studied Electrical Engineering
at TU Delft and obtained his
doctorate in smart temperature
sensors. He then became a
product designer at the chipcompany National Semiconductor
and a senior researcher at theHolst Centre in Eindhoven. After
returning to research, he hadthat digitise the ultrasound signals first,
potentially making the flow of informationeven more efficient. ‘You can compare it to
the development of telephony: we used tomake calls using analogue telephones. That
telephone conversation is now digital. In
the past, only this telephone signal passed
through the same cable, but now we also
receive broadband internet and around ahundred television channels directly into thehome. Possibilities like that also apply in thisfield. Ultrasound probes are the old-fashioned
analogue telephones. In medical equipment,
the digitisation of data is still in its infancy.’

the opportunity of a positionas associate professor back at
TU Delft. In it, he combines his
expertise as a chip designer withultrasound research.

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Wireless
All of that miniaturisation and reducing the number of cables: surely these chips could also
communicate wirelessly? Pertijs: ‘That depends on how much data you need to transmit. An
incontinence plaster only needs to transmit an estimate of the bladder volume every ten minutes.
That can easily be done wirelessly. But with real-time imaging, you’re talking around tens ofgigabits per second. That’s a completely different order of magnitude.’ In addition, wirelessultrasound can sometimes be counter-productive. ‘A catheter always has a guide wire aroundit to push and pull it through the bloodstream. Some cables could easily run through a wire like
that, making a wireless signal unnecessary. However, probes that the doctor holds by hand willcertainly be wireless in the future. Our chips will be able to make an important contribution tothat development.’‘Ultrasound probes are the old-fashioned
analogue telephones. In medical equipment,
the digitisation of data is still in its infancy.’

Energy-efficient
But there is a downside to these increasingly smarter, smaller

About ultrasound scanning

ultrasound device, which combines several echoes

Ultrasound is known from the animal world: bats

into an image, for example of a foetus in the womb.

also use it. They emit ultrasound that reflects off

An individual echo is comparable to a depth

their prey. That reflection – or echo – returns tomeasurement from a boat: if you throw a leadthe bat after a time. The time between transmitting

weight on a rope into the water, you know how

working with our partners on energy-efficient, safe chips.’and receiving is a measure of the distancedeep the water is by measuring the length of

between the bat and its prey. This principle can berope. By doing the same kind of measurement

Cross-fertilisationtranslated to ultrasound scanning: a probe withfrom several boats, you gain an image of the river

It is through collaboration with partners that Michiel Pertijs

a sound transmitter and receiver, a transducer,

or seabed. This is similar to a two-dimensionalemits ultrasound. When the ultrasound signal hits

ultrasound image of an object in the body: the boata surface between two tissues, it reflects back. The

is the transducer and the rope is the route taken bytransducer receives the echo and transmits it to thethe sound.

chips: processing all of the data streams on a mini-surface
consumes a lot of energy. And this needs to go somewhere,
in the form of heat. Although this is not a problem with large
ultrasound equipment, it is not ideal in or on the patient. ‘Heat
can result in tissue damage,’ says Pertijs. ‘This is why we areachieves the greatest progress. ‘We are often working on thesame problem from different perspectives. This means that wereach solutions that we would not have come to individually.’
Using chip technology to create superfast ultrasound images
is an example of this. This in turn can be used for new medical
diagnostics. ‘There is cross-fertilisation that you only find in
this type of project. The bigger picture it gives us enables us
to make more progress towards the medical application. I findthat extremely motivating.’

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A glimpse into the universe
with superconducting
electronics

29

Text: Dave Boomkens | Photography: Mark Prins

Questions like How did the universe come into being? andWhere do we, humans, come from? can be approached in two
ways: philosophically and scientifically. Scientifically this isdone by looking at light – very old light. ‘And to do that you needsuperconducting detectors and sensitive measuring equipment,’
says Professor Jochem Baselmans. ‘Only then can you get
answers to what may be the most relevant questions in our
universe.’

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‘The Galileo example shows that new instruments lead to new discoveries,
and that new discoveries lead to new insights.’

Mankind has been trying to understand the universe for centuries. The early Babylonians made an attempt, but
the best-known example is perhaps Galileo Galilei. In 1610, he used a telescope made by spectacle maker Hans
Lipperhey from the Dutch town of Middelburg to gaze at the stars. ‘Galileo bought the telescope at a market in
Venice, disassembled it and made it thirty times more powerful,’ says Baselmans. ‘Galileo spent days studying thefour great moons of Jupiter until he was certain: the moons orbited Jupiter. His discovery demonstrated that not
everything in space revolves around the Earth and undermined the geocentric world view that was considered trueat that time. The Galileo example shows that new instruments lead to new discoveries, and that new discoveries
lead to new insights. Since then, astronomy has been the branch of science in which new technology is applied
the fastest by far.’

New insights
New instruments enable us to get a better understanding of
the way the universe came into being. According to Baselmans,
this technology is simply indispensable. ‘After all, you can’t just
fly through the universe or study a star in a laboratory. Because
observation is quite difficult in astronomy (huge distances,
weak signals) and experimentation is not possible (having
two galaxies collide to see what happens), technology is thekey.’ Until the 1970s, the focus was on photographic plates,
but development of Charge Coupled Devices, known as CCDs,
marked the dawn of a new era: that of highly sensitive lightdetectors. ‘All of a sudden, astronomers were able to capture
images and spectra of very weak objects. Just try to find a newplanet or a new asteroid: you have to detect movement among
one of those ten-million dots above you. This is much easier to

About Jochem
Jochem Baselmans gave his
inaugural address on 11 October
2019. He has a shared position,
spending 50% of his time working
for TU Delft and the other 50% for
SRON. The combination of these
two institutes makes it possible
to develop revolutionary new
instruments. The big challenge:
developing integrated circuits
based on superconducting

do with a computer than with photos.’

electronics that combine radiation

Best in the world

on a single chip. This makes it

This semiconductor technology can be purchased. ‘There’s

possible to create the broadband

a whole industry behind it,’ Baselmans explains. ‘It is used by
Ministry of Defence, and also by commercial photographers.
But much of the radiation from the universe is not visible light

coupling, filtering and detection

camera spectrograph mentioned
in the text. This is also known as
an imaging spectrometer.

and is emitted at other wavelengths. An important example issubmillimetre radiation, also known as far-infrared radiation.
In order to detect this radiation, you need superconducting
detectors and chips. It is not possible with semiconductor
technology. But those superconducting detectors only workat very low temperatures; temperatures close to absolute zero(-273.15 degrees Celsius), which makes this technology too
expensive and difficult for most applications. So you only use
it if you really want to understand each ray of light, and that’s

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The Atacama Submillimeter
Telescope Experiment (ASTE). A
far infrared camera – developed in
Delft – is installed inside the ASTE
telescope.

SCAN!

‘When I obtained my doctorate in 2002,
telescopes like the Hubble – which now orbits theearth like a satellite – and ALMA were booming.’

Far infrared

Hubble & Alma

Why is it so important to work with infrared light?

The Hubble Telescope was used to take many optical

What does far infrared tell us about the universe?

and near-infrared photographs of the universe. And we‘To answer those questions, I will first give you a

now also have ALMA: the Atacama Large Millimeter/

short history lesson about the universe,’ Baselmans

submillimeter Array, an advanced telescope that cancontinues. ‘The universe was created about 13.8 billion

detect far-infrared radiation from some of the coldest

years ago with the Big Bang – a hot ball of plasma that

objects in the universe. In order to do that, ALMA uses

grew bigger and bigger in a very short period of time.

superconducting technology developed partly atWith the exception of the afterglow of the Big Bang,TU Delft and partly at SRON. ‘ALMA measures far-the cosmic microwave background, the universe wasinfrared light with a very high spatial and spectral

still dark. Then the universe cooled down. The cooling

resolution. To put it into simpler terms: ALMA canof the universe enabled the formation of the elementtake very sharp pictures (spatial) and measure thehydrogen, and the universe became transparent toprecise type of radiation on each ‘pixel’ based onlight. With the birth of the very first stars, the lights

the wavelength (spectral). These spectroscopic

went on in the universe. All the other elements wereobservations make it possible to create a new image

formed in the cores of those stars, and the supernovaof the universe.’ Scientists looking to find out more

explosions that destroyed them. So we’re all stardust!

about the early beginnings of our universe need toWith far-infrared light you can look at the oldest stars

measure infrared light which has taken between 2 andand all generations of stars that came into existence

10 billion years to reach earth. Sensitive instruments

what I want! I want to help answer questions like Where do we come from?

immediately afterwards. By studying that, you gain

are required for this. Jochem Baselmans is working on

and that can only be done with superconducting detectors for submillimetre

knowledge about the oldest galaxies, and also about

super­conductive and extremely sensitive measurement

radiation. To make these detectors, I have a great partnership with the Terahertz

the birth of planets and other galaxies.’

equipment that can speed up the current measurement

Sensing group at TU Delft. This group includes two of the best in the world inprocess 100-fold. Once it all works, we will be able tothe field of quasi-optics and electromagnetism, namely Andrea Neto and Nuria

create 3D maps of star systems, allowing us to look

Llombart.’

back in time and space.

Missing link
According to Baselmans, the knowledge Andrea and Nuria have is the missing
link in his expertise. ‘A telescope consists of one or two large mirrors that
send light into the cabin of the telescope. To get that radiation into my super­
conducting chips properly, I need the knowledge of the Terahertz Sensing group.
For example, one of Nuria’s PhD students designed the optics for DESHIMA– the Deep Spectroscopic High-redshift Mapper. DESHIMA, a chip about thesize of two euro coins, is used to measure the distances and ages of distantgalaxies. This is done by measuring different shades of infrared light. In October
2017, under the watchful eye of my colleague Akira Endo, researchers fitted thischip to the ASTE telescope in Chili.’

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Photo of the DESHIMA chip. Cooled to 0.1 degrees
Kelvin, this small chip measures a spectrum in farinfrared. Previously, this could only be done withsystems of about half a meter in size.

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189‘I want to help answer questions like Where do we comefrom? and that can only be done with superconducting
detectors for submillimetre radiation.’

Imaging spectrometerto take into account when designing DESHIMA.

DESHIMA is another type of spectrometer that can

For example, we converted and tested a cooler.

very well be used in combination with a telescope likeIn addition, you need reading electronics. Those

Alma. Although DESHIMA measures radiation at aelectronics aren’t something you can just buy, andmuch lower spectral resolution, it does so at a muchthere isn’t any fundamental research either... no...

higher bandwidth. This enables DESHIMA to determinethat’s high-level engineering. You also have to be able

the distance to far-infrared galaxies and to gather

to understand the physics of the chips. I learned a lot

knowledge about star formation in dust-enshrouded

about that from Teun Klapwijk, the expert in the field ofgalaxies. ‘The nice thing about DESHIMA is that we

nanotechnology. Once you have a good understanding

now have a spectrometer that is as small as a lens,of a chip and are able to read it, you still have to makeand it works. For the time being, we are still working

sure the light reaches the right place. Otherwise, ofwith one pixel, but one of the next steps will be placing

course, it’s no use to you at all. With current quasi-

a large number of lenses side by side. Each lens will

optical techniques, this is not possible for the large

then have its own spectrometer. This way we will

bandwidth of the future imaging spectrometers.

increase the number of pixels from 1 to 25. Or perhaps

Fortunately, we are working hard on that in EEMCS. In

to 100! This then becomes an imaging spectrometer.’fact, over the past two-and-a-half years, my colleague

Into space
If the imaging spectrometer meets all expectations, theuniverse beckons. And to go into space, you have to be

Nuria Llombart of the Terahertz Sensing group has
been working on finding out how this can be done atall. Turns out it’s very difficult.’

at SRON: the Netherlands Institute for Space Research,

The power of EEMCS and SRON

which is where Baselmans spends about half of his

But working in Delft and at SRON offers more, says

time at work. ‘We also have to find someone who is

Baselmans. For example, there are two large clean­crazy enough to build a telescope that can be cooled

rooms in Delft where all kinds of things can be

down to 4 Kelvin,’ laughs Baselmans. ‘That’s about

tried out. In addition, SRON provides a great deal

269 degrees (Celsius) below zero. So you have toof knowledge and experience in the field of spacelaunch a fridge into space, which, with the help of

instrumentation. He also wants to do more in the fielda number of solar panels, is able to keep the wholeof single processing in the near future. ‘Once you havemirror at 4 Kelvin. Otherwise, the radiation from thethe ideal instrument, how do you then make sure you

telescope will blind your detectors. What we are doing

can make astronomical observations with it? How

now works up to 1 Terahertz. But if you go into space,

do you ensure that you’re not affected by noise in theyou want it to work up to at least 10 Terahertz. There’s

detectors or particles drifting through the atmosphere?

still a lot of homework for us there.’

And what if you want to work with 50,000 detectors

CoolerHigher purpose
The reason for Baselmans’ interest in superconducting
electronics is related to his PhD research. ‘When I obtained
my doctorate in 2002, telescopes like the Hubble – which now
orbits the earth like a satellite – and ALMA were booming.
At that time, Terahertz technology with superconductors was
cutting edge, while my PhD research was quite fundamental.
What I missed while working on my PhD was an interesting
context. I’m more into creating. I love making new things, butthey have to be useful; they have to serve a higher purpose.
Questions such as How did the universe come into being? andHow does everything fit together? serve that purpose. It doesn’t
get more relevant than that.’at the same time? How are you going to get your dataprocessed quickly enough? How do you ensure that

So, superconducting technology, which only works

algorithms work as efficiently as possible? The latter isin extremely cold conditions, can help us obtain an

something I don’t know much about at all. Fortunately,

advanced picture of the universe. ‘This ridiculously

a lot of that expertise can also be found at TU Delft andlow temperature was also something that we had

I can always pop in to ask my colleagues this question.’

190

In October 2017, Dutch and Japanese researchers
mounted this special chip on the Japanese ASTE
telescope in North Chile. The superconducting chip isdeveloped by Delft University of Technology and SRON,
Netherlands Institute for Space Research. The chip
contains one antenna, 49 filters and 49 detectors. The
antenna captures radiation of various wavelengths.
The filters unravel the radiation in 49 tones of infrared.
The 49 detectors measure the intensity of the radiation.
When a detector picks up a signal, it can be seen as apeak in a graph.

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191

We\Visit: combatting
loneliness with video-calling30

Text: Dave Boomkens | Photograph: Frank Auperlé

Visiting a loved one who’s critically ill: normally that’s possible, but due tothe coronavirus, visiting ICUs is no longer permitted. The result is a lonely
fight behind closed doors. In an attempt to combat the loneliness, researchers
at Delft University of Technology have come up with We\Visit: a tool thatfacilitates video-calling by appointment. And it was developed at lightning
speed after the Reinier de Graaf hospital sounded the alarm.

It all began on a Friday afternoon, shortly after Dutch Prime Minister Rutte‘Our collaborative
partnerships
enable us to makemore progress
towards a medical
application. I findthat extremely
motivating.’announced the ‘intelligent lockdown’. A researcher the university’s Faculty of
Mechanical, Marine and Materials Engineering (3ME) forwarded an email to ElifÖzcan Vieira. Elif, who works for the Faculty of Industrial Design Engineering(IDE) and whose research interests include alarm fatigue among medical
personnel, opened the message and immediately felt the hairs of her arms
stand on end. ‘It was a pretty emotional email,’ Elif explains. ‘A cry for help. The
Reinier de Graaf hospital said that it was in dire need of a communication toolfor its ICU. The patients were not only suffering from the coronavirus, it said,
but also from loneliness. That’s a heartrending combination, and I immediately
felt that I had to get to work. The research experience I’d gained at various ICUs
would certainly be useful, but I needed help; I needed technical knowledge to beable to develop such a tool.’Interfaculty cross-fertilisation
A colleague put Elif in touch with Willem-Paul Brinkman. Working just 650 metres along thecampus, Willem-Paul uses virtual technologies in his work combatting phobias and psychotic
disorders at the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS).
That very same weekend, he drummed up a number of fellow scientists, who attended a Zoom
meeting with him and Elif the following Monday. One of them was Merijn Bruijnes, a psychologist
specialising in the interaction between people and technology. Merijn: ‘The email from the Reinierde Graaf hospital created a stir, and immediately led to a brainstorming session. We soon cameup with the idea of video-calling including a planning tool. But the question remained: who would
we be making such a tool for?’

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‘Protecting patients’ privacy isalso an important element.’

No mobile phones
In order to reach the right target group, the researchers
contacted, among others, the FCIC – a Dutch foundationthat promotes the interests of ICU patients and their loved
ones. Elif: ‘ Often people admitted to intensive care don’t
have access to a mobile phone. After all, they had to berushed to hospital. And there’s also the fact that corona
patients are often aged 65 or older.’ Merijn adds that many
corona patients in the ICU are in an induced coma. ‘Someof the patients have been intubated and are attached to

About Elifbreathing apparatus. That looks very intimidating, but

Elif Özcan-Vieira is the director of TU Delft’s Criticalsomeone from the foundation explained that this doesn’t

Alarms Lab (CAL), and is the Care Technology Leadnecessarily mean that people are no longer taking anythingat the Adult Intensive Care Department of Erasmus

in. So how do you adapt your tool to that?’

Medical Centre. In the article A beautiful alarm beside

Cybersecurity

your hospital bed, Elif explains that a cacophony ofsounds can cause alarm fatigue among medical

The brainstorming session produced a very specificpersonnel and anxiety in patients. In collaboration

concept: in order to create a feeling of social contact andwith the Erasmus MC, she aims to address theprovide emotional support to loved ones, the scientists

problem of noise pollution in ICUs with human-wanted to make an online video tool. On a number ofcentered design solutions that rely on advanced

points, this video tool would take up where FaceTime andtechnologies. During her student days in Ankara,

WhatsApp left off. Not only can the tool be used easily bywhen she studied Industrial Design, she fell in love

those aged over 65, for example, but protecting patients’with both radio and sound. ‘There’s a mysterious

privacy is also an important element. ‘The Cybersecurity

magic to sound: its shape, its apparent elusiveness,group put forward a number of students who did their best

its direct effect on the immediate surroundings. As

to hack the tool’s security protection. They reported theira sound designer at Radyo ODTÜ, which was thenfindings and then came up with solutions. That proved tobeing run by students and has now grown to be a

be really helpful.’

national station, I became fascinated by the tiny

Prototypevibrations that we catch with our ears. In the years
that followed, I began to learn more about productOne week after the Monday afternoon session, theperception, human behaviour and psychologicalresearchers had a prototype. Its name? We\Visit. And how

processes – and sound kept cropping up in that

does it work? Merijn explains: ‘The family’s contact person

context, too.’is given a code by the nursing staff. The patient’s family

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195

can use this code to log in to the We\Visit system toschedule a virtual appointment. When it’s time for the‘What do healthcare staff
require? And what do family
members at home want?’

appoint­ment, someone from the nursing staff – or a
volunteer – takes a tablet to the patient to start thevideo connection at their bedside. As with Zoom, there
is a virtual meeting space where people can talk toeach another. The tricky thing is that you’re dealing withan ICU environment, which means that many things are
not possible. In the beginning, we were still thinking
really big, but we eventually came up with quite aOpen science

simple design, developed by IDE student Marek Torbus

The application used for video-calling, Jitsi, is a so-and implemented by EEMCS students, all on a pro bono

called open source application, which means thatbasis and in addition to their exams. In no time at all,anyone can use it. And sharing is a method that fits

my colleague Otto Visser (of the Distributed Systems

perfectly with the We\Visit team’s approach. Elif: ‘At theGroup) had ten students in his app saying they reallymoment, we’re seeing physical borders closing all overwanted to work on this. It was incredibly special.’

the world, and countries rapidly turning inwards to helpthem­selves. With this open science approach, we want
to transcend national borders. It isn’t just our virus, but

About Merijn

everyone’s virus. Although we’re making a technicalproduct, this is all about the need to solve a social

Merijn Bruijnes is a psychologist and member of the

problem. That’s why open science is so incrediblyInteractive Intelligence group at TU Delft. ‘When it comesim­portant during this corona crisis.’ This vision is

to computer science, people often think of hardcore

endorsed by Merijn: ‘From the outset, we all agreed

programming or machine learning, not psychology. It’s

that everyone should be able to use our findings. At

nevertheless the case that you can use psychologicalpresent, we’re running a We\Visit pilot at the Reinier deknowledge to make technology work more effectively.

Graaf hospital, and we’ll soon be able to test a more

Take the example of making a system user-friendly.

finely tuned version at Rotterdam’s Erasmus Medical

More and more organisations are working with chatbots

Centre. If we’re satisfied after the pilots, we want toor virtual assistants. By researching how people respondrelease the software, so that any stakeholder from any

to digital interlocutors such as these, technology can beorganisation will only need to download a package

used to contribute to psychology.’ One good example ofof information. A ready-made package will soon be

how psychology and technology can come together isavailable on our website.’the tool that Merijn developed for the Police Academyin Apeldoorn. He devised a virtual suspect that could be

Packagesused by trainee police officers to practise various cross-

Elif has first-hand evidence of the need for ready-madeexamination techniques. In this way, there is no needpackages such as this. ‘Last week I spoke to one offor up-and-coming officers to exchange their textbooks

my uncles, who is developing tests to detect hepatitis

for the interrogation room straight away; instead, thisin a lab in Turkey. We discussed the current pandemic

provides a great intermediary step. Merijn’s current

that’s setting the world ablaze. When I told him about

research focuses on diabetes patients. ‘Often, we only

We\Visit and the software packages that everyone

consider the patient and the doctor, but that means wewould soon be able to use, he immediately said: ‘OK,

miss the bigger picture. That’s because patients also

let me know when it’s ready, because this has to comeinteract with a social environment. ‘How can I tell my

to Turkey.’ We hope that soon, We\Visit will not only bedaughter that she’s allowed to bake cookies, but I’m notused in hospitals, but also in care homes and nursing

allowed to eat them?’ I’m therefore mainly looking at how

homes, both in the Netherlands and much further

you can improve this exchange between patients andafield.’their social environment.’

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The design of We\Visit, developed
by IDE student Marek Torbus, isdeliberately simple.

About Cédric and Marek
Cédric Willekens is studying computer science at TU Delft, and wasintroduced to the We\Visit project by Otto Visser. ‘Shortly after COVID-19
took hold in the Netherlands, I moved in with my girlfriend. We often
talked about her grandmothers, and how to keep in touch with loved
ones at a time of social distancing. When I heard Otto Visser talking
about We\Visit, I immediately knew that it was a fantastic project andthat I wanted to contribute. The great advantage is that, as a student
assistant, I’ve been working on educational software projects for sometime now. One of those projects is called Queue. Queue is a tool thatyou can use to schedule contact time with students; if there’s an oral
exam coming up, for example. The basic idea of Queue is similar tothat of We\Visit. At the outset, in very close cooperation with the Reinier

Bringing a smile

de Graaf hospital, we tried to make an inventory of the needs. What dohealthcare staff require? And what do family members at home want?

Until then, however, there’s a lot of hard work to come. Elif:Based on this input, we wrote the back-end – the part that’s not visible to‘We’ve received some funding from the TU Delft COVID-19

the user. The industrial designers focus on the user interface and try to

Response Fund, but we’ll soon need to think about long-

make the digital environment as user-friendly as possible. That includes

term financing too. After all, we could do so much more withasking questions like: what buttons does the device need? Which route

We\Visit. We could create a ‘message in the bottle’ function, forwill the user take? They make things intuitive, make sure there’s a sleek

example. We see that young children in particular can become

design, and form the link between us – the computer scientists who are

extremely shy when faced with a camera. They would much

responsible for the technical implementation – and users.’

rather sing a song for granny in a familiar context, or take the‘We see that young
children in particular
can become
extremely shy when
faced with a camera.
They would muchrather sing a song for
granny in a familiar
context, or take thetime to create acheerful drawing.’

time to create a cheerful drawing. With a ‘message in the bottle’

The design of We\Visit, developed by IDE student Marek Torbus, isfunction, the family wouldn’t need to come together at thedeliberately simple. Marek: ‘I was really interested in doing this projectsame time, but you could send different messages throughout

because of its current need. I talked to Elif about doing something to

the day. We\Visit would combine them and deliver them as ahelp and was lucky enough to join the team from the beginning. My‘message in a bottle’. But developing something like that will

main responsibility was to create a workflow and user interface for ourtake time.’ Merijn: ‘In order to put all these great ideas into

service. The main requirements were to make the website accessible

practice, we will indeed need a business plan. Our colleagues

for different users, especially taking into account the elderly who haveat the Faculty of Technology, Policy and Management (TPM)

difficulties in dealing with technology or don’t have a smartphone whichmight be able help us with that in due course. I do believe

makes it very difficult for them to communicate with their family andthat it is going to work. When you see how willing everyone

friends when in the ICU. In order to fulfil this, the website has been

is to get involved, it’s really inspiring. For now, the key thing isdesigned with the minimal possible steps needed to connect families

to reduce the pressure on the ICUs. Doctors and nurses arewith the patients. And I also used for example very contrasting colours.

currently working one exhausting shift after another, and until

The key to our success has been daily Zoom meetings where I had the

now there’s been little room for the human aspect. We hope

opportunity to present work and receive immediate feedback from thethat We\Visit will change that, and provide a reason for a smile

team. I’m particularly honoured to be a part of We\Visit.’

without having to sacrifice anything – or anyone.’198

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199

EEMCSNODESVOLUME II
Copyright © 2020 TU Delft
CONCEPT AND DESIGN

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200

EEMCSNODESVOLUME IIThis book contains a time-based selection of the scientific research thattakes place at the Faculty of Electrical Engineering, Mathematics andComputer Science (EEMCS). EEMCS is the faculty where bits and bytes
are converted into real solutions for people and society. And that is
desperately needed. Because our safety, health and well-being depend
more and more on technology. The scientists of EEMCS are working,day-to-day, on smart solutions to global problems and do not shy awayfrom any challenge. They change the world and make impact. They are ourheroes. They tell our stories. They are the creators of the future.
tudelft.nl/eemcs@EEMCS_TUD
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