Jan M Baetens

Ghent University | UGhent · Department of Data Analysis and Mathematical Modelling

In order to describe the sensitivity of a cellular automaton (CA) to a small change in its initial configuration, one can attempt to extend the notion of Lyapunov exponents as defined for continuous dynamical systems to a CA. So far, such attempts have been limited to a CA with two states. This poses a significant limitation on their applicability,...

Wildfires, as a global phenomenon, are an integral part of the Earth system which affects different regions of the planet quite unevenly. They are of great concern in Europe: in the European Union alone, over 4000 km2 of our land were burnt in 2019; 3400 km2 in 2020; 5000 km2 in 2021. Depending on the proximity to where people live, and the extent...

In this work we extend our previously developed compartmental SEIQRD model for SARS-CoV-2 in Belgium. The model is geographically stratified into eleven provinces and a telecommunication dataset provided by Belgium's biggest operator is used to incorporate interprovincial mobility. We introduce variants, seasonality, and vaccines in our model, as t...

Moisture performance is an important factor determining the resistance of wood-based building materials against fungal decay. Understanding how material porosity and chemistry affect moisture performance is necessary for their efficient use, as well as for product optimisation. In this study, three complementary techniques (X-ray computed tomograph...

Background The identification of tropical African wood species based on microscopic imagery is a challenging problem due to the heterogeneous nature of the composition of wood combined with the vast number of candidate species. Image classification methods that rely on machine learning can facilitate this identification, provided that sufficient tr...

Bio-based building materials are susceptible to degradation by decay fungi when exposed to favourable conditions for fungal growth. The risk of decay depends on both the environmental conditions and material resistance. Although durability data is available for solid wood, standard tests mainly focus on mass loss assessment after a fixed degradatio...

Given that social interactions drive the spread of infectious diseases amongst humans, one anticipates that human mobility in Belgium affected the spread of COVID-19 during both 2020 "waves". Measures against this spread in turn influenced mobility patterns. In this study, we analyse and mutually compare time series of COVID-19-related data and mob...

Background: The identification of tropical African wood species based on microscopic imagery is a challenging problem due to the heterogeneous nature of the composition of wood combined with the vast number of candidate species. Image classification methods that rely on machine learning can facilitate this identification, provided that sufficient t...

In this report, we bring our epidemiological models in line with the additional measures taken between November 22nd, 2021, and January 28th, 2022, and reassess their impact on the fourth Belgian COVID-19 wave. A larger reduction of leisure contacts results in a faster decrease of COVID-19 hospitalizations and a lower overall burden of disease for...

In this report, we use two epidemiological models to explore the relative effects of three non-pharmaceutical interventions between November 17th, 2021, and December 24th, 2021 on the COVID-19 related hospitalizations during the fall and winter of 2021 in Belgium. Although the healthcare system will most likely not be overwhelmed by the fourth CO...

Classification is one of the most important problems in the theory of CA. For instance, assessing how CA design choices impact the generated dynamics requires an overview of the types of dynamics that can occur. Nevertheless, an overview and critical comparison that includes works from the last five years is currently lacking. This paper provides s...

We present a compartmental extended SEIQRD metapopulation model for SARS-CoV-2 spread in Belgium. We demonstrate the robustness of the calibration procedure by calibrating the model using incrementally larger datasets and dissect the model results by computing the effective reproduction number at home, in workplaces, in schools, and during leisure...

Objectives The coronavirus disease 2019 pandemic has had a major impact on our society, with drastic policy restrictions being implemented to contain the spread of the severe acute respiratory syndrome coronavirus 2. This study aimed to provide an overview of the available evidence on the cost-effectiveness of various coronavirus disease 2019 polic...

We present a novel method to study two-dimensional rotation-symmetric number-conserving multi-state cellular automata with the von Neumann neighborhood with radius one. This method enables a succinct and easy enumeration in all cases examined so far in literature, i.e., cellular automata with at most five states. Moreover, it allows to find all suc...

This report describes the combined impact of different social distancing scenarios, the 501Y.V1 variant and the ongoing vaccination campaign in Belgium and illustrates the importance of epidemic control in the period up to August 1, 2021. • Changing social distancing behaviour as a result of lifting measures too soon might, in spite of the ongoing...

Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper-oceanic response to the passage of Hurr...

The extinction of ecosystems and the mechanisms that support or limit species coexistence have long been studied by scientists. It has been shown that competition and cyclic dominance among species promote species coexistence, such as in the classic Rock-Paper-Scissors (RPS) game. However, individuals’ mobility and the underlying topology that defi...

Cryptic species are morphologically identical but genetically distinct, and are prominent across numerous phyla. The coexistence of such closely related species on local scales would seem to run counter to traditional coexistence and competition theory; it has been hypothesized as a consequence of differences in their resource use or tolerances to...

Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper oceanic response to the passage of the...

The effect of fungicidal components in wood has been known for ages, yet there is no method to assess the impact of such components on the durability of a wood species, as compared to other material characteristics that influence decay. In this paper, the importance of fungicidal effects on the natural durability of 10 wood species is assessed in r...

In this work we assessed the spatio-temporal variability of the oceanographic conditions in the period 1998–2017 in four sectors of the Exclusive Economic Zone (EEZ) of Cuba, referred to as the northwest, northeast, southwest and southeast sectors (i.e., NWS, NES, SWS and SES, respectively). We relied upon remote-sensing observations of wind speed,...

As a response to a rapidly rising number of SARS-CoV-2 infections, the Belgian government imposed strict social contact restrictions on March 13th, 2020. After nearly two months, the curve was succesfully flattened and social restrictions were gradually released. Unfortunately, pharmaceutical interventions are not yet available so it is expected th...

Predicting kiln-drying schedules for a given wood species is not yet possible, despite many research efforts. This is mainly due to insufficiently considering important spatio-temporal variables such as moisture and temperature gradients, and wood anatomical features during drying in the predictive modelling framework. To understand the influence o...

This paper concerns d-dimensional cellular automata with the von Neumann neighborhood that conserve the sum of the states of all their cells. These automata, called number-conserving or density-conserving cellular automata, are of particular interest to mathematicians, computer scientists and physicists, as they can serve as models of physical phen...

Passive acoustic telemetry data are used to study animal movement in aquatic environments, but tools to process the data are limited. In areas that are too large to be fully covered by the limited detection ranges of receivers or acoustic listening stations, researchers generally assume that animals are residing in an area when they are detected fr...

An understanding of the oceanic response to tropical cyclones is of importance for studies on climate change, ecological variability and environmental protection. Hurricane Irma (2017, Atlantic Ocean) broke many records, including the fact that it was the first category 5 hurricane making landfall in Cuba since 1924. In this study, we assess the oc...

We present a simple approach for finding all number-conserving two-dimensional cellular automata with the von Neumann neighborhood. We demonstrate the efficiency of this approach by enumerating and describing four special cases: totalistic, outer-totalistic, binary and three-state cellular automata. The last result was not published before. We then...

In recent decades, large wildfires have inflicted considerable damage on valuable Natura 2000 regions in Belgium. Despite these events and the general perception that global change will exacerbate wildfire prevalence, this has not been studied yet in the Belgian context. Therefore, the national government initiated the national action plan on wildf...

Traditionally, fungal growth dynamics were assessed manually, limiting the research to a few environmental conditions and/or fungal species. Fortunately, more automated ways of measurement are gaining momentum due to the availability of cheap imaging and processing equipment and the development of dedicated image analysis algorithms. In this paper,...

Individual-based modelling is an increasingly popular framework for modelling biological systems. Many of these models represent space as a lattice, thus imposing unrealistic limitations on the movement of the modelled individuals. We adapt an existing model of three competing species by using a lattice-free approach, thereby improving the realism...

Many disciplines rely on testing combinations of compounds, materials, proteins, or bacterial species to drive scientific discovery. It is time-consuming and expensive to determine experimentally, via trial-and-error or random selection approaches, which of the many possible combinations will lead to desirable outcomes. Hence there is a pressing ne...

In this work, we analysed the satellite-based responses of sea surface temperature (SST) and chlorophyll-a (chl-a) concentration in the waters of the Exclusive Economic Zone (EEZ) of Cuba to hurricanes that crossed the EEZ between 1998 and 2016 as well as the environmental drivers governing the post-storm responses. We considered two spatial scales...

We present a novel representation of 1D reversible and number-conserving cellular automata with four states. Carrying this view over to two dimensions, we are able to construct 65 four-state reversible and number-conserving 2D cellular automata with the von Neumann neighborhood. A clever use of the split-and-perturb decomposition of number-conservi...

Motivated by the high turnover rate of the Eurasian eagle owl (Bubo bubo) population in the south of the province of Limburg, the Netherlands, which is linked to extremely high concentrations of PCBs (polychlorinated biphenyls) and DDE (dichlorodiphenyldichloroethylene) found in owl carcasses, a habitat suitability (HS) assessment for this region w...

In this paper, the identification problem of diploid cellular automata is considered, in which, based on a series of incomplete observations, the underlying cellular automaton rules and the states of missing cell states are to be uncovered. An algorithm for identifying the rule, based on a statistical parameter estimation method using a normal dist...

Seasonal influenza is a worldwide public health concern. Forecasting its dynamics can improve the management of public health regulations, resources and infrastructure, and eventually reduce mortality and the costs induced by influenza-related absenteism. In Belgium, a network of Sentinel General Practitioners (SGPs) is in place for the early detec...

In this work, we analysed the satellite-based responses of sea surface temperature (SST) and chlorophyll-a (chl-a) concentration in the waters of the Exclusive Economic Zone (EEZ) of Cuba to hurricanes that crossed the EEZ between 1998 and 2016. We considered two spatial scales to capture the spatially heterogeneous nature of the effects of hurrica...

This paper concerns $d$-dimensional cellular automata with the von Neumann neighborhood that conserve the sum of the states of all their cells. These automata, called number-conserving or density-conserving cellular automata, are of particular interest to mathematicians, computer scientists and physicists, as they can serve as models of physical ph...

This report present basic criteria that could be used for the estimation of wildfire risk at the pan-European level. The report has been elaborated in consultation with the national experts in the Expert Group on Forest Fires and represents a first attempt on establishing critical variables that may help in characterizing areas in the pan-European...

Theoretical and experimental research studies have shown that ecosystems governed by non-transitive competition networks tend to maintain high levels of biodiversity. The theoretical body of work, however, has mainly focused on competition networks in which the outcomes of competition events are predetermined and hence deterministic, and where all...

Helical inserts or baffles in tubular membranes can provide flux increases without additional energy usage. However, the optimal shape of these turbulence-enhancing structures remains debated, with many experimental studies being performed, though few full-scale applications reported. A model-based approach can assist experimental work in getting d...

In this paper, the problem of identifying the cellular automata (CAs) is considered. We frame and solve this problem in the context of incomplete observations, i.e., prerecorded, incomplete configurations of the system at certain, and unknown time stamps. We consider 1-D, deterministic, two-state CAs only. An identification method based on a geneti...

In 1997, Eurasian Eagle Owls Bubo bubo returned to Limburg, the south-eastern province of The Netherlands. However, since then the population size has stagnated, while extremely high concentrations of PCBs have been found in Eagle Owl carcasses. These observations suggest that a further expansion of the species in Limburg is under threat. The high...

This paper presents a wildfire ignition probability map for Belgium that may serve as a proxy for wildfire risk. Wildfires have proven to cause considerable damage to valuable Natura 2000 areas in Belgium in the past, and the prevalence of such events is anticipated to increase in the future. Therefore, a risk map can be used to optimize the alloca...

This report contains the annual summary of the fire season of 2017 with official figures provided by 33 contributing countries for the number of fires, burnt areas and fire prevention efforts, and the analysis of fire danger and areas mapped in the European Forest Fire Information System (EFFIS).

In this paper, the classical density classification problem is considered in the context of affine continuous cellular automata. It has been shown earlier that there exists no general solution to this problem that is valid for any number of cells. Here, we consider this problem in the case of a fixed number of cells. Necessary conditions for solvin...

Background Persistent declines in migratory songbird populations continue to motivate research exploring contributing factors to inform conservation efforts. Nearctic-Neotropical migratory species’ population declines have been linked to habitat loss and reductions in habitat quality due to increasing urbanization in areas used throughout the annua...

Diversity is a concept central to ecology, and its measurement is essential for any study of ecosystem health. But summarizing this complex and multidimensional concept in a single measure is problematic. Dozens of mathematical indices have been proposed for this purpose, but these can provide contradictory results leading to misleading or incorrec...

Using experimental data obtained from in vitro bioaugmentation studies of a sand filter community of 13 bacterial species, we develop an individual-based model representing the in silico counterpart of this synthetic microbial community. We assess the inter-species interactions, first by identifying strain identity effects in the data then by synth...

This volume constitutes the thoroughly refereed proceedings of the 24th IFIP WG 1.5 International Workshop on Cellular Automata and Discrete Complex Systems, AUTOMATA 2018, held in Ghent, Belgium, in June 2018. The 10 regular papers presented in this book were carefully reviewed and selected from a total of 16 submissions. The papers highlight the...

Biodiversity is a key factor underpinning the stability and productivity of microbial ecosystems. However, the mechanisms that give rise to and maintain biodiversity in microbial communities are not yet fully understood. The individual-based model (IBM) developed by Reichenbach et al. [1] has been used extensively in literature to investigate biodi...

The density classification problem is one of the most studied problems in the context of the computational abilities of cellular automata. Since this problem cannot be solved in the classical sense, we consider a weaker version, by slightly relaxing the assumptions on the output specification. In this paper, we discuss this relaxed problem for two-...

•Key messagePattern recognition has become an important tool to aid in the identification and classification of timber species. In this context, the focus of this work is the classification of wood species using texture characteristics of transverse cross-section images obtained by microscopy. The results show that this approach is robust and promi...

We used mathematical models of photosynthesis to quantify the effects of ultraviolet (UV) radiation on the photosynthetic potential of Prochlorococcus and Synechococcus marine cyanobacteria living at 0° and 40°N/S latitude. We show that UV is an environmental stressor for these organisms near the ocean surface, accounting for roughly two-thirds of...

We present necessary and sufficient conditions for a cellular automaton with a von Neumann neighborhood of range one to be number-conserving. The conditions are formulated for any dimension and for any set of states containing zero. The use of the geometric structure of the von Neumann neighborhood allows for computationally tractable conditions ev...

Describing complex phenomena by means of cellular automata (CAs) has shown to be a very effective approach in pure and applied sciences. Most of the applications, however, rely on multidimensional CAs. For example, lattice gas CAs and lattice Boltzmann methods are widely used to simulate fluid flow and both share features with two-dimensional CAs....

Biodiversity has a critical impact on ecosystem functionality and stability, and thus the current biodiversity crisis has motivated many studies of the mechanisms that sustain biodiversity, a notable example being non-transitive or cyclic competition. We therefore extend existing microscopic models of communities with cyclic competition by incorpor...

Loss of habitat to urbanization is a primary cause of population declines as human-dominated landscapes expand at increasing rates. Understanding how the relative effects of different conservation strategies is important to slow population declines for species in urban landscapes. We studied the wood thrush Hylocichla mustelina, a declining forest-...

Most fungi grow by developing complex networks that enable the translocation of nutrients over large distances. Spatially explicit mathematical models are able to capture both the complexity of the fungal network and the biomass evolution, as such providing a powerful alternative to classical modelling paradigms. Unfortunately, most of these models...

‘The 100 km Dodentocht’, which takes place annually and has its start in Bornem, Belgium, is a long distance march where participants have to cover a 100 km trail in at most 24 hours. The approximately 11 000 marchers per edition are tracked by making use of passive radio-frequency-identification (RFID). These tracking data were analyzed to build a...