Joost Mertens 

• 5 december 2024
• 16.30 uur
• ​Stadscampus - Willem Elsschotzaal, Hof van Liere ​
• Promotor: prof. dr. Joachim Denil 
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Digitale tweelingen zijn digitale representaties van dingen in de werkelijkheid, denk aan machines, fabrieken, gebouwen en zelfs mensen. Met de huidige trends zal je ze binnen enkele jaren meer en meer zien opduiken in allerlei facetten van ons leven. Deze digitale tweelingen beloven de gebruiker allerhande nuttige diensten, zoals het bekijken van historische data, het optimaliseren van processen en het voorspellen van de nabije toekomst. Voor deze diensten berusten ze in veel gevallen op gedetailleerde modellen van het werkelijke systeem. Het is dus belangrijk dat deze modellen correct zijn, of dat ze mee evolueren naarmate het werkelijke systeem evolueert. Daarnaast veranderen de diensten die een gebruiker van de digitale tweeling verwacht continu, dus ook op dat vlak is er evolutie. In deze thesis presenteren we technieken om om te gaan met deze twee soorten van evolutie van digitale tweelingen, en we demonstreerden deze op een schaalmodel van een havenkraan.

Oskar Seuntjens 

• dinsdag 8 oktober 2024
• 16.00 uur
• ​Stadscampus - Klooster van de Grauwzusters - Gebouw S ​
• Promotoren: prof. dr. Amaryllis Audenaert & dr. Matthias Buyle
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

We maken volop de transitie naar een circulaire economie die ervoor pleit om materialen en producten zo efficiënt mogelijk te gebruiken. Helaas zien we dat schoolgebouwen vaak leegstaan. Dit doctoraat onderzoekt hoe we schoolgebouwen maximaler kunnen gebruiken, bijvoorbeeld door de lokale gemeenschap nauwer in het gebouw te betrekken. In het bijzonder wordt onderzocht welke ventilatiestrategiën een flexibel gebouwgebruik op een duurzame manier kunnen faciliteren.

Karina Seguel Suazo 

• dinsdag 1 oktober 2024
• 13.00 uur
• ​Stadscampus - Klooster van de Grauwzusters - Gebouw S ​
• Promotoren: prof. dr. Jan Dries & dr. Thomas Dobbeleers​
  
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

My research focuses on the field of biological wastewater treatment. The effectiveness of wastewater treatment plants (WWTPs) is heavily influenced by the microbial communities that drive these processes. Therefore, understanding the roles these microorganisms play is crucial. Despite significant progress in this field, industrial WWTPs continue to experience operational challenges, often due to gaps in our knowledge of the microbial communities. One key issue is poor liquid-solid separation, commonly known as bulking sludge, which can disrupt plant performance.  

The aim of this thesis was to gain deeper insights into the microbial communities in industrial WWTPs by combining both fundamental and applied research approaches. I examined the bacterial communities in 29 industrial WWTPs in Flanders, Belgium, identifying key functional groups, with a particular focus on bacteria involved in sludge structure and settling properties. Special attention was given to two dominant filamentous bacteria in activated sludge, Thiothrix and Leptothrix.

To study Thiothrix, I conducted applied research using laboratory-scale sequencing batch reactors (SBR) under controlled conditions, to explore their impact on sludge structure and sulfur cycling. In the case of Leptothrix, my research was more fundamental, investigating the diversity, abundance, and metabolic potential of the most common Leptothrix species in activated sludge systems globally.

Kostas Anastasiades 

• woensdag 30 september 2024
• 17.00 uur
• ​Campus Groenenborger- lokaal g.T.103 ​
• Promotoren: prof. dr. Amaryllis Audenaert & prof. dr. Johan Blom​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Half of all the annually excavated raw materials worldwide is destined for the construction industry, rendering this a critical industry for the depletion of earth’s resources. In addition, our society is going through a modal shift in terms of transportation means where walking and cycling are prioritised. Therefore, many new cycling and pedestrian bridges are needed to literally bridge unsafe and uncomfortable crossings on land and over water. This PhD research thus investigates how circularity assessment can aid in designing circular pedestrian bridges. Within this global investigation, three subtopics were the main focus: 1. The development of a material volume prediction methodology to assess the efficiency of a bridge’s structural design. The aim is to reduce material consumption by designing efficient structures. 2. The development of a service life prediction model that can be used to assess the remaining service life of bridge components. The aim here is to promote the reuse of components before turning to virgin materials. 3. Reuse is only possible when components are standardised, at least to some extent. In addition, procedures for the disassembly and certification of reusable components need to be established. Following these three major research topics, a framework is presented that designers can use to move towards a circular and more sustainable construction industry.

Jens de Hoog

• vrijdag 25 september 2024
• 16.30 uur
• ​Campus Middelheim - lokaal m.G.010
• Promotoren: prof. dr. Peter Hellinckx & prof. dr. Siegfried Mercelis​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Artificiële Intelligentie (meer bepaald Machine Learning) heeft zich al meerdere malen bewezen om heel goed te kunnen presteren in veel verschillende toepassingen: denk maar aan zelfrijdende auto’s of robots. Hoewel deze AI’s goed presteren in perfecte situaties (zoals perfect weer met matig zonlicht), worden ze al snel veel slechter in minder goede situaties zoals regen, sneeuw of nieuwe omgevingen. In mijn onderzoek toon ik aan dat verschillende AI’s allemaal anders reageren op verscheidene situaties. Dat maakt dat elke AI goed kan zijn in één bepaalde situatie, maar dan slecht in een andere. In mijn onderzoek kies ik op basis van de situatie de AI die volgens de voorspelling het best zou presteren. Als ik zo voor elke situatie de juiste AI kies, kan ik aantonen dat algeheel betere prestaties verkregen worden voor veel verschillende situaties.

Abdil Kaya 

• woensdag 11 september 2024
• 16.00 uur
• ​Campus Middelheim - lokaal m.G.010
• Promotoren: prof. dr. Maarten Weyn & prof. dr. Rafael Berkvens​
  
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Met de toenemende verstedelijking en de daaruitvolgende drukte op evenementen is het schatten van mensenmassa's tijdens evenementen cruciaal voor veiligheid en beheer. Dit proefschrift hanteert een methode die radiofrequentiesignalen (RF) gebruikt om mensen te tellen. Een nadeel van zulke systemen is de nood aan referentietellingen in nieuwe omgevingen. De onderzoeksstappen die werden gezet om die afhankelijkheid weg te werken, worden uiteengezet in dit proefschrift.

Cédric Lecluyse

• dinsdag 10 september 2024
• 17.00 uur
• KU Leuven (Gebroeders de Smetstraat 1, 9000 Gent) - lokaal E036 (groot auditorium)
• Promotoren: prof. dr. Michael Kleemann (KU Leuven) & prof. dr. Ben Minnaert (UAntwerpen)​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Draadloze energieoverdracht biedt de eindgebruiker voordelen zoals meer gebruiksgemak, minder slijtage en esthetiek. Voor toepassingen, varierende van consumentenelektronica tot zware automatisch geleide voertuigen, kunnen twee soorten nabije veldkoppeling worden gebruikt: magnetische velden (inductieve koppeling) en elektrische velden ( capacitieve koppeling). Dit proefschrift richt zich op capacitieve koppeling, in het bijzonder de invloed van een vast materiaal op de efficientie en het frequentiebereik van capacitieve draadloze energieoverdracht.

De grootste uitdaging bij capacitieve draadloze energieoverdracht is het bereiken van voldoende vermogensdichtheid ondanks de lage koppelcapaciteit. In de huidige literatuur wordt de koppeling beschreven door een ideaal pi-model, waarbij geen rekening wordt gehouden met verliezen in het medium en de frequentieafhankelijke permittiviteit. Hoewel dit model goed is wanneer lucht als medium wordt gebruikt, is het niet geschikt voor vaste media zoals polymeren.

Dit proefschrift maakt gebruik van het algemene pi-model en beschouwt de dielek­trische frequentieafhankelijke eigenschappen van media. Orn deze dielektrische eigenschappen te verkrijgen, wordt een experimentele laboratoriumopstelling gerealiseerd. Deze opstelling kan automatisch metingen uitvoeren over afstanden van 1 mm tot 300 mm voor frequenties tussen 100 kHz en 20 MHz. Verder worden deze meetgegevens verwerkt in een geoptimaliseerd ontwerp van een capacitief draadloos energieoverdracht systeem. Op basis van analytische berekeningen wordt een demonstrator gebouwd met als doel om meer dan 100 W over afstanden van 1 mm tot 10 mm over te brengen door lucht en vaste media: epratal, PTFE en epratex.

De demonstrator is in staat om 180 W door de lucht over te dragen over een afstand van 2 mm met een systeemefficientie van 61. 7%. Ter vergelijking: een vermogensoverdracht van 160 W wordt bereikt door 2 mm dik epratal met een efficientie van 75. 7%. Uit de simulaties en metingen in dit proefschrift kan warden geconcludeerd dat epratal een gunstige invloed heeft op capacitieve draadloze vermogensoverdracht. De verliezen die optreden in het vaste medium zijn ondergeschikt aan de verliezen in de externe componenten zoals de spoelen.

Priyesh Pappinisseri Puluckul

• woensdag 4 september 2024
• 16.00 uur
• ​Stadscampus - Klooster van de Grauwzusters - Gebouw S ​
• Promotor: prof. dr. Maarten Weyn​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

The proliferation of the Internet of Things (loT) coupled with the demand for de­ ploying more sophisticated and energy-consuming applications on these tiny, resource­ constrained devices have raised concerns over their reliance on batteries for energy. When powered with batteries, either primary cells or secondary cells, loT devices are short-lived, requiring regular battery replacements to ensure extended lifetime. This is a complex af­ fair, consuming both time and money alike. On top of it, batteries dumped from millions of loT devices pose severe environmental threats. With the discourse of sustainability be­ coming increasingly prominent, the ecological damage projected by the discarded batteries from loT devices has drawn intense criticism. Liberating loT from the constraints of de­ pleting batteries necessitates the development of technologies that support ever-operating devices. Consequently, the concepts of Energy Harvesting and the Internet of Batteryless Things (loBT) were introduced. Energy harvesting allows scavenging energy from otherwise untapped ambient energy sources such as solar, heat, vibrations, etc., for the perpetual op­ eration of loT devices. By relying on alternate energy buffers such as capacitors or superca­ pacitors for energy storage, batteryless architectures free loT devices from the shortcomingsof battery-powered systems.

The reliability of an loBT device, like in any other systems design, pivots on the energy source. However, ambient sources are unpredictable and often intermittent. While there are a multitude of ambient sources available, the choice of energy source is practically constrained by the nature of the end application. However, an loBT design doesn't need to rely solely only on a single source of energy. Scavenging energy from multiple sources makes the system design more resilient by augmenting its energy budget or providing a backup when one of the sources ceases to supply energy. Hence, an efficient loBT design will rely on the most feasible energy source while preserving the choice of alternative sources. This thesis explores the viability of alternative energy sources, delving into the intricacies of rarely tapped energy sources and investigating the feasibility of multisource energy harvesters, along with introducing novel test and evaluation tools for loBT development.

Solar energy, due to its abundance and limitless supply, has become the primary choice of renewable energy source for many loBT applications. However, there are many situations where solar energy is not the ideal choice due to its dependency on direct sunlight, sensitivity to shadows and daytime exclusivity. Fortunately, there exists another source of energy that has been often underappreciated, particularly for outdoor loBT devices, the temperature difference between the soil and air. Due to the distinct thermal properties of soil and air, the temperature of the soil always lags behind the air, creating a consistent temperature difference between both. Unlike solar radiation, this temperature gradient is available during the day and night, making it ideal for many low-power applications. This thesis presents an in-depth discussion on soil-air thermal energy harvesting through a series of deployments, data collection, simulations and loBT prototypes working with soil-air thermal energy. Ad­ ditionally, with an extensive data set on soil and air temperatures and utilizing analytical models, the feasibility of soil-air thermal energy harvesting is further discussed.

While an loBT design can benefit from harvesting energy from multiple sources, they are often restricted to a single source due to the lack of Power Management Units (PMU) with multi-source harvesting support. Harvesting energy from multiple sources requires a PMU that can simultaneously harvest and combine energy from multiple sources and man­ age the load and storage without consuming extra energy. This thesis introduces lnfiniteEn, a multisource energy harvesting architecture that uses an efficient energy combiner to allow harvesting from many sources at the same time. Additionally, lnfiniteEn accommodates a re-configurable storage architecture that can be configured on the run with the help of a novel Load Monitoring Module (LMM). The LMM can track the energy state of the load and adjust the energy buffer as required. Along with this, a harvest rate sensor incorporated with the lnfiniteEn can give an accurate estimate of the harvesting rate in real time, empowering energy-ware designs to exploit the knowledge of input energy and manage its tasks efficiently. All these features incorporated into lnfinteEn come with negligible energy overhead, mak­ ing it a potential candidate for batteryless designs. Moreover, the entire architecture is built using commercial-off-the-shelf (COTS) components, allowing easy customization and replication.A flawless loBT design requires rigorous testing and validation before it is taken to the field. In addition, the knowledge of ambient energy sources in the deployment area can facilitate the right choice of harvesters and energy buffers. In this context, this thesis introduces two tools, µMeter and TEGBed. µMeter is a portable energy surveying tool that can be deployed along with the energy harvester to measure the harvested energy and to analyze the potential of ambient sources. Whereas TEGBed is an emulation tool specifically designed for thermal energy harvesting devices for accurately recreating thermal energy harvesting situations in the lab.

In general, this thesis advances the state-of-the-art energy harvesting and batteryless systems by making numerous contributions that include, (i) a feasibility assessment study and a simulation model for soil-thermal energy harvesters along with a detailed analysis us­ ing diverse real-world data sets (ii) two novel tools, µMeter and TEGBed to enhance the testing and deployment of batteryless devices, and (iii) an efficient multisource power man­ agement architecture / nf i niteE n that incorporates functionalities such as load monitoring and harvest rate sensing for energy-aware system design.

Jalal Faghih Mohammadi Jalali 

• maandag 15 juli 2024
• 13.00 uur
• ​Stadscampus - lokaal s.C.101 & 002
• Promotoren: prof. dr. Jeroen Famaey & prof. dr. Rafael Berkvens​
  
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

In today’s world, achieving reliable wireless communication is crucial but challenging. This work introduces Intelligent Reflecting Surfaces (IRSs), a groundbreaking technology poised to transform connectivity. IRSs act as smart, invisible "mirrors" that precisely bend and direct wireless signals, ensuring strong connections by overcoming obstacles. ,

An IRS consists of a sophisticated planar array with numerous passive or active elements that individually manipulate electromagnetic waves, reshaping the wireless signal propagation environment. By adjusting the phase and amplitude of these elements, an IRS can steer signals toward intended receivers, creating optimized communication paths even when direct Line of Sight (LoS) is obstructed. This capability enhances connectivity in various environments, from urban areas to indoor spaces, while reducing energy consumption due to its passive operation.

This work presents IRS as a key enabler for advanced technologies, enhancing their performance and efficiency. IRS improves power efficiency in multi-user Simultaneous Wireless Information and Power Transfer (SWIPT) networks, supporting both energy harvesting and data transmission. Integration of IRS into Ultra-Reliable Low-Latency Communication (URLLC) and Machine Type Communication (MTC) systems significantly reduces latency and increases reliability. Additionally, IRS benefits Virtual Reality (VR) users by mitigating path loss or blockages, ensuring immersive experiences without latency or quality loss.

IRS also optimizes Mobile Edge Computing (MEC) by improving signal delivery for efficient edge data processing. This is critical for applications requiring instantaneous feedback and high data integrity, such as autonomous vehicles and industrial automation. The work explores IRS deployment across a broad frequency spectrum, from Frequency Range 1 (FR1) to Frequency Range 2 (FR2), including millimeter-Wave (mmWave) and TeraHertz (THz) frequencies, highlighting its profound impact on future telecommunications.

To evaluate IRS-assisted networks, this work defines Key Performance Indicators (KPIs) such as data rate, power efficiency, energy efficiency, Signal-to-Interference-plus-Noise Ratio (SINR), transmit signal power budget, and received power strength. These KPIs help assess and optimize network performance through efficient resource allocation policies. Addressing the non-linear, non-convex, and Mixed Integer Nonlinear Programming (MINLP) problems associated with resource allocation, the work employs strategies to simplify and solve these complex problems. Techniques like convex relaxation and approximation are used to make these problems more manageable.

Algorithms developed in this work solve the optimization problems either globally or sub-optimally, using optimization solvers and simulations. Advanced mathematical tools, such as the big-M method and Successive Convex Approximation (SCA), are employed to linearize and approximate non-convex terms. Iterative solutions refine resource allocation designs, ensuring optimal performance despite initial complexity.

Simulations demonstrate the performance improvements achievable through IRS-assisted networks, validating theoretical models and confirming practical feasibility. By exploring various IRS configurations and their implementation in different environments, the study showcases IRS's adaptability and versatility. This work establishes IRS as a pivotal technology, enhancing SWIPT networks, URLLC, MTC, MEC, VR, mmWave, and THz applications, paving the way for robust, efficient, and engaging communication ecosystems.
Low threshold translation: meaning/potential for society in English: Intelligent Reflecting Surfaces (IRSs) revolutionize connectivity by enhancing wireless communication reliability, reducing energy consumption, and enabling advanced technologies like VR, autonomous vehicles, and smart cities. This innovation promises more efficient, eco-friendly, and robust communication systems, significantly improving daily life and technological progress for society.

Ben Moins

• donderdag 4 juli 2024
• 17.00 uur
• ​Campus Middelheim - lokaal m.G.010
• Promotoren: prof. dr. Amaryllis Audenaert & prof. dr. Wim Van den bergh​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

In 2020, the European Commission launched its Green Deal, aiming for Europe to become the first climate-neutral continent by 2050. A big part of this plan involves the construction industry, which is responsible for about 40% of global greenhouse gas (GHG) emissions. Specifically, roads contribute over 15% of worldwide emissions and are one of the main users of resources in Europe. Since 90% of European roads are paved with asphalt, the asphalt industry plays a crucial role in reducing these emissions.

The main idea of this research is that for the road industry to become more sustainable, it needs to use fewer new materials and carefully study the impacts of its processes from the start. This dissertation focuses on using life cycle assessment (LCA) and life cycle cost analysis (LCCA) to examine pavement designs that include recycled asphalt. It tackles two main challenges: optimizing the recycling of asphalt and evaluating the benefits of using more recycled asphalt in new roads. The goal is to create a comprehensive approach that combines LCA, LCCA, and the use of recycled asphalt to make the road industry more sustainable.
The study of existing research highlighted the growing importance of LCA and LCCA in making pavement construction more sustainable. However, it found inconsistencies and gaps in these methods, such as the lack of standard rules and varying system boundaries for assessments. It also emphasized the need to consider the full life cycle of materials, including their end-of-life phase. Moreover, the study explored how to combine LCA and LCCA into a single measure through putting a monetary value on environmental impacts.

The research found that environmental impacts shift throughout the different phases of a pavement's life, highlighting the importance of considering the entire life cycle, especially when using waste materials. Key environmental impacts include global warming, fine particulate matter, fossil resource scarcity, and human health risks. The study suggested that focusing on these factors could simplify LCA for green public procurement, but care should be taken due to the shifting.

The dissertation underscores the need to include durability in the sustainability of asphalt pavements. It explored three methods to account for material performance: adjusting layer thickness while keeping the same service life, finding break-even points with performance evaluation, and using detailed service life predictions. Results showed the importance of holistic modelling that considers both material quality and sustainability. Comparing standard service life estimates with predicted service life revealed that conservative estimates might undervalue the impact of performance on sustainability.

The research stressed the urgency for the asphalt industry to take immediate action to achieve net-zero emissions by 2050. An industry-wide study showed that GHG emissions could be reduced by up to 23.7% yearly by 2030, and up to 40% with the best available technologies. However, achieving carbon neutrality requires economically viable and proven strategies, highlighting the need for urgent action and innovation.
The dissertation emphasized the importance of using recycled asphalt to reduce environmental and economic impacts in road construction. Recycled asphalt can replace both new bitumen and aggregate without major production changes. The study found that the end-of-waste location, where recycled asphalt changes from waste to a secondary material, affects various impact modules. This shows the complexity of sustainability comparisons in pavement studies. Simulations suggested that higher recycling rates improve pavement durability, though results vary with different mixtures and recycling rates. Overall, the integration of recycled asphalt is crucial for improving pavement sustainability across different layers and mixtures.

Simon Vanneste

• woensdag 3 juli 2024
• 17.00 uur
• ​Stadscampus - Klooster van de Grauwzusters - Promotiezaal 
  
• Promotoren: prof. dr. Siegfried Mercelis, prof. dr. Peter Hellinckx ​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Er zijn veel problemen in de wereld waarin verschillende gedistribueerde systemen moeten samenwerken om een doel te bereiken. Nu artificiële intelligentie een steeds grotere rol begint te spelen in ons leven, bekijken we hoe we dit kunnen gebruiken bij het ontwikkelen van deze gedistribueerde systemen. In dit onderzoek bekijken we hoe we verschillende intelligente entiteiten (agenten) kunnen laten samenwerken en communiceren met elkaar. Om de agenten te leren communiceren en hoe ze zich moeten gedragen maken we gebruik van reinforcement learning. Bij reinforcement learning leren de agenten welke acties ze moeten ondernemen aan de hand van de beloning die ze krijgen. Dit laat de agenten toe om een op maat gemaakt communicatie protocol te leren dat volledig geïntegreerd is met de getrainde agenten. In het eerste deel van de thesis hebben we onderzocht hoe we dit soort methodes kunnen gebruiken in reële applicaties. Daarnaast hebben we verschillende algoritmes ontwikkeld voor het leren van een communicatie protocol. Tot slot hebben we bekeken hoe we dit soort systemen op een gedecentraliseerde manier kunnen trainen. 

Michaël Hillen

• vrijdag 14 juni 2024
• 16.00 uur
• ​Campus Groenenborger- lokaal g.T.129
• Promotoren: prof. dr. Gunther Steenackers & prof. dr. Geert Van der Snickt​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Active infrared thermography (AIRT) is a non-destructive imaging method that can reveal information about the internal structure of an object. Here it was used to study wooden panel paintings by visualizing damage to the paintings and the structure of the wooden support. An automated mobile measurement system was developed for measuring large paintings in situ. This system was employed to study several paintings from the collection of the Royal Museum of Fine Arts Antwerp (KMSKA). The AIRT results were compared to other established imaging methods in the field: X-ray radiography (XRR), infrared reflectography (IRR), and macroscopic X-ray fluorescence (MA-XRF). Ultimately, it was shown that AIRT provides complementary information to these methods and would be a valuable addition to the conservator’s toolkit.

Zakarya Kabbara

• vrijdag 14 juni 2024
• 15.00 uur
• ​Campus Middelheim - lokaal m.G.010
• Promotoren: prof. dr. Ivan Verhaert & dr. Sandy Jorens​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

This research introduces a new method for optimizing the design of HVAC ductwork systems for both new buildings and renovations. Using advanced simulations, this method identify optimized designs that enhance the system's performances while also minimizing its life cycle costs.

Erik Verreycken

• donderdag 6 juni 2024
• 17.00 uur
• ​Campus Middelheim- lokaal m.A.143 (aula Patrice Lumumba)
• Promotoren: prof. dr. Jan Steckel & prof. dr. Walter Daems​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

To an electronics engineer, the world around us is quantified using sensors. These sensors fall into two main categories: passive, where existing phenomena are measured, and active, where the system emits a signal itself. Active sensing modalities include sonar, which emits sound and records echoes with microphones to sense objects, GPS that triangulates receiver position using time delays from satellite signals, and MRI, utilizing strong magnetic fields to visualize the interior of a human body. In contrast, passive sensing modalities require no signal emission and instead rely only on existing phenomena for measurement. Examples include cameras, microphones, seismometers, and magnetic compasses.

Passive acoustic localization refers to a set of measurement techniques utilizing pre-existing audio to localize and analyze the audio source. Typically, a microphone array is employed. Spatial variation in the microphone locations, i.e. two microphones cannot be placed at the same position, result in slight differences in the recorded audio at each microphone. These differences can manifest as timing disparities, attributed to varying sound travel distances to each microphone, or differences in intensity due do microphone position and the radiation pattern of the sound source, i.e. the difference in audio strength depending on the angle. Analyzing these differences allows deducing properties of the sound source, including position, path, point of acoustic focus, radiation pattern, etc.

The main advantage of passive localization is that it can be deployed unobtrusively, i.e. without disturbing the sound emitting object that is being studied. In biological applications, this means there is no need to capture the animal to attach sensors to it. In industry, this means no machines have to be brought down to be retrofitted with sensors. In public infrastructure, this means no major infrastructure works and downtime are needed. The main advantage of acoustic localization is that it can be applied to any animal, object, etc. that emits sound and only these already occurring sounds are needed to perform the analysis.

The main reason for us to study passive acoustic localization is that it enables us to study animals in their natural environment. Passive acoustic localization allows us to study bats without disturbing their natural behavior. We can just sit by areas that are frequented by bats, set up our array and investigate what makes them the aerial acrobats that they are.

The main downside of passive acoustic localization is that it can only be performed when the animal/object is making a sound. This limits the applicability of passive acoustic localization to vocalizing animals during their vocalizations or larger animals that make sound by moving physically. Passive acoustic localization is therefore very well suited to study animals that use vocalizations for navigation, such as bats and some species of cetaceans. A second downside is that passive acoustic localization is limited in range based on the amplitude and directionality of the sound source. To overcome this problem, larger and denser arrays or networks of microphones must be constructed. Conventionally, these arrays are constructed with expensive microphones and using expensive hardware, which can limit the size or number of microphones that can be deployed in a single experiment. Furthermore, in larger microphone arrays, it may not be possible to capture or sample all microphones using the same recording device. This in turn can create disparities in the timings of the recorded audio, which has an adverse effect on the algorithms used for passive acoustic localization, many of which require a very high degree of synchronization. Finally, the algorithms as passive acoustic localization described throughout the literature and this thesis require the microphone positions to be known because the accuracy of the algorithm depends on the accuracy to which the microphone positions are known. Retrieving the microphone position may not be a trivial task when the array is constructed in a remote area, or may require a considerable amount of error-prone human work to measure all microphone positions.

The key contributions of this thesis are situated around the development of a framework that allows the construction of microphone arrays for passive acoustic localization in a biological context. The framework is composed of a novel hardware platform that enables the construction of microphone arrays of (nearly) arbitrary size, and the framework is able to collect data in a manner that allows for acoustic localization and other methods of analysis. We also optimized our array for end-user convenience.

The first contribution is the development of a hardware platform for the construction of microphone arrays. We have explored the usage of MEMS microphones that are orders of magnitude cheaper than current commercial solutions. In this thesis, we prove that these MEMS microphones can be used for acoustic localization and analysis of acoustic signals. We further prove that the platform can be used to create microphone arrays of nearly arbitrary size.

The second contribution deals with data collection and synchronization. In any system dealing with acoustic localization, knowing the timing of the acoustic signal is critical. We created a novel synchronization technique by adding a synchronization channel to our data that can be wired or wireless and that enables us to synchronize data from different microphones/sensors in a post-processing step.

The third contribution is about the usability of the system, which can be split in two sub-contributions. The first is automatic spatial array calibration. We exploit the fact that our small-scale arrays can be described as a collection of microphones, i.e. an array with six degrees of freedom, instead of individual microphones with each three degrees of freedom. We also propose a calibration tool that can exploit those properties to get a quicker, more robust calibration of the array. The second sub-contribution is situated in some key concepts that enable us to write better, more efficient algorithms. The terms small-scale array and large-scale array are introduced to describe different kinds of arrays, which are constructed using the same hardware components, but their differences can be exploited in software to analyze or localize acoustic signals in a more efficient way.

Finally, the fourth contribution is the performance of a biological experiment with the framework on the hunting behavior of pallid bats. This experiment shows a significant effect of the surface roughness, on which a prey is placed, on the capture efficiency of pallid bats which use trawling behavior. These results were published in Nature Communications Biology.

Ivan De Boi

• woensdag 29 mei 2024
• 15.30 uur
• ​Campus Middelheim- lokaal m.A.143 (aula Patrice Lumumba)
• Promotoren: prof. dr. Rudi Penne & dr. Pieter Jorissen
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

On the usage of probabilistic machine learning methods for calibrating 3D measuring devices based on straight lines.

Furkan Elmaz

• dinsdag 28 mei 2024
• 16.00 uur
• ​Stadscampus - Hof van Liere - F.de Tassiszaal
• Promotoren: prof. dr. Siegfried Mercelis, prof. dr. Peter Hellinckx & prof. dr. Mumin Enis Leblebici
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Artificial Intelligence (AI) has been at the forefront of recent technological advancements. Various sectors have started integrating AI into their workflows and this transformation has been expected to increase at an accelerating pace. However, certain industries have been struggling to adopt AI despite its promising potential documented in the literature. Especially industrial processes with strict constraints and infrastructural inertia show a strong tendency towards more conventional, reliable and time-tested methods. This situation creates a "gap" between academic AI research and industrial practice. This thesis aims to investigate and tackle this gap by addressing the needs and limitations of industrial process control applications from a pragmatic perspective.

This thesis is structured around three core pillars: modeling, optimization, and explainability. In the modeling pillar, we propose a completely data-driven hybrid AI methodology to efficiently combine expert knowledge with real-life data to address the data variance limitation. The proposed methodology is applied to an HVAC use case to predict indoor temperature. The optimization pillar proposes the use of Reinforcement Learning (RL) in a pharmaceutical process and shows its potential as a process optimization tool even in the case of multiple constraints. This pillar was also verified experimentally in a real-life plant, further proving its practical viability. Lastly, the explainability pillar proposes an Explainable AI framework, aiming to generate human-understandable explanations from the RL agent which not only increases the transparency and trustworthiness but also allows us to gain insights and pave the way to enhancing our fundamental knowledge about the process itself.

Through the integration and utilization of these pillars, a cyclical pattern reveals itself, where our fundamental knowledge and real-life data, when combined, allow us to develop accurate and reliable predictive models. Then the utilization of RL for optimization enables us to find novel and more performant strategies that are capable of outperforming more conventional approaches. Finally, with the application of XAI, we can unpack and understand the new strategies RL generates which further deepen our fundamental understanding of fueling the next cycle. Therefore, going beyond resolving the resistance towards AI applications, this thesis also aims to propose to sustainable and iterative approach to gradually integrate AI into industrial process control workflow. Thus, aiming to make AI from a "magical" tool to a crucial asset that can be effectively utilized.

Giulia Moggia

• Maandag 22 april 2024
• 17.00 uur
• ​Campus Drie Eiken- lokaal d.O.06
• Promotor: prof. dr. Tom Breugelmans​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

Carbohydrates are renewable, inexpensive and available organic raw materials. Only 3–5% of them have industrial use, the rest decays and recycles along natural pathways. One interesting finding in this field has been the recognition that acids derived from sugars have potential uses in fine chemistry. The biggest challenge in the use of carbohydrates as raw materials in fine chemistry is to achieve their direct and region-selective oxidation in aqueous media, which is difficult by classical chemical methods without a preliminary protection strategy. Electroorganic approaches have currently fascinated academicians and industrial researchers because of their high potential prospects for industrial ventures. Electrocatalytic organic synthesis provides a powerful tool to control the reaction rate and selectivity through electrode potential and current, and represents a promising alternative to the traditional industrial methods. In fact, electrosynthesis is naturally suited to obey the principles of Green Chemistry, owning to several environmentally favorable features: i.e., reduced energy consumption, use of renewable raw materials, decreased emission of pollutants or toxic raw materials.
Despite its sustainable nature and its potential to electrify the industry, as such replacing traditional, non-sustainable production processes of a broad range of fine chemicals, electrochemical synthesis methods are still very underdeveloped as compared to their traditional alternatives. More research is needed to better understand electrochemical processes and address the main challenges that prevent their application at industrial scale: i.e., the still unsatisfactory selectivity and/or productivity, the electrodes’ limited lifetime and the insufficient know-how on up-scaling towards industrial scale.
This PhD thesis is specifically dedicated to the study of electrocatalytic routes for the selective oxidation of glucose to gluconic and glucaric acid (both of which are commercially relevant carbohydrates). The aim here is thus to investigate the factors that determine the selectivity of the reaction towards the two products of interest, including the choice of the catalyst and the reaction conditions, and, as such, unravel the reaction mechanism beyond it. To this end, a combination of electrochemical and analytical techniques is used where microscopical surface analysis, used for the morphological characterization, is linked to its electrocatalytic performance.

Mehrdad Moradi

• Woensdag 17 januari 2024
• 16.00 uur
• Campus Middelheim - lokaal m.G.010
• Promotoren: prof. dr. Joachim Denil​
• Faculteit Toegepaste Ingenieurswetenschappen

Abstract

The validation of the safety properties of Cyber-Physical Systems (CPS) requires tremendous effort, as the complexity of cyber-physical systems is increasing. A well-known approach for the safety validation of CPS is Fault Injection (FI). Fault injection is a testing technique that aids in understanding how the system behavioral when stressed in an unusual way. The goal of fault injection is to find a catastrophic fault that can cause the system to fail by injecting faults into it. These catastrophic faults are less likely to occur, and finding them requires tremendous labor and cost, as fault space is enormous and multidimensional. Therefore, traditional fault injection methods are not effective in terms of number of found faults and severity of them.
In this thesis, we utilize simulation-based fault injection in the system models, which enables the test engineer to identify the fault in the early phase of system development. We first performed a systematic literature review to categorize the existing methods, fault models, metrics for system models. Then, we propose a fault injection method to inject faults into the MATLAB/Simulink model as white-box models using model transformation. We also worked on the fault injection in black-box models, which is based on Functional Mock-up Interface (FMI). Next, we investigated multiple methods to increase the efficiency (in terms of total number of critical faults and run time execution) of fault injection using sensitivity analysis, reinforcement learning (RL), and the Generative Adversarial Network (GAN). These methods utilize high-level domain knowledge of the model under test to set up the fault injection simulation. The proposed methods automatically configure faults in the model under test and find catastrophic faults that can violate the safety properties of the model in the early stage of system development.
We compared the proposed method (RL-based and GAN-based) with random-based fault injection, and our proposed method outperformed random-based fault injection in terms of the severity or number of faults found.
We also demonstrated our method in Hazard Analysis and Risk Assessment (HARA), specified in ISO 26262 (functional safety standard in automotive), identifies malfunctions that could lead to hazards, and rates their risks.