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Om allerlei chronische niet-overdraagbare aandoeningen zoals cardiovasculaire ziektes, diabetes, overgewicht en kanker te voorkomen heeft de mens nood aan een bepaalde hoeveelheid fysieke activiteit. Al sinds het ontstaan van de mensheid werd voldoende fysieke activiteit gehaald uit dagelijkse bezigheden, zij het in de oudheid door jagen en eten verzamelen, of in modernere tijden door fysieke inspanningen op het werk of door het uitvoeren van huishoudelijke taken. De fysieke inspanning tijdens vele van deze dagelijkse bezigheden is in de hedendaagse samenleving echter sterk afgenomen door de automatisering van zowel de werk- als de privéomgeving. Ondanks de vele voordelen van deze automatisering ondervindt de globale bevolking dan ook één groot nadeel: het gebrek aan fysieke activiteit en de daarmee verbonden risico’s voor de menselijke gezondheid. Dit eindwerk kadert dan ook in het doel naar het vinden voor een alternatief om voldoende fysiek actief te zijn. Concreter worden de volgende twee onderzoeksvragen opgesteld: Ten eerste wat is de hartslagrespons tijdens het sportvissen op activiteiten die typisch zijn voor het vissen met een vaste hengel en een werphengel onder gecontroleerde omstandigheden? Ten tweede wat is de hartslagrespons tijdens het sportvissen op activiteiten die typisch zijn voor het vissen met een vaste hengel in de praktijk? In een eerste experiment werd de fysieke activiteit op basis van hartslag en 3D acceleratie geschat tijdens het simuleren van hengelen met een vaste hengel en het simuleren van actief hengelen met een werphengel en kunstaas op roofvis. Ter vergelijking werden hartslag en 3D acceleratie ook gemeten tijdens rustperiodes en wanneer er gewandeld werd. Uit de resultaten bleek dat voor het simuleren van hengelen met de vaste hengel de hartslag wel hoger lag ten opzichte van de rustperiodes, maar dat deze gemiddeld gezien 20.00% (75 BPM ten opzichte van 90 BPM) onder de hartslag tijdens het wandelen bleef. Enkel tijdens het simuleren van hengelen met de werphengel steeg de hartslag significant in vergelijking met deze tijdens het wandelen (respectievelijk 90 BPM en 94 BPM, of dus een stijging van 4.44%). Het actief hengelen met een werphengel lijkt dan ook een inspanning te zijn met voldoende fysieke activiteit. In een tweede experiment werd er effectief gevist langs de waterkant. Er werd geopteerd om enkel met de vaste hengel te vissen en dit op stromend water aangezien dat het meest voorkomende type hengelen is in Vlaanderen. Opnieuw werden hartslag en 3D acceleratie gemeten tijdens het experiment om nadien te kunnen vergelijken met rust. Opvallend was dat dit maal de hartslag gemiddeld gezien lager lag tijdens het hengelen dan tijdens de rustperiodes, namelijk 2.94% in vergelijking met de hartslag tijdens het zitten en 14.71% met die tijdens het staan. Hier kon dus uit afgeleid worden dat het hengelen met een vaste hengel eerder een relaxerende en dus anti-stresserende werking heeft, maar dus geen oplossing biedt voor het probleem van de fysieke inactiviteit. De fysieke activiteit tijdens het recreatief sportvissen is dus sterk afhankelijk van het type hengelen waarvoor geopteerd wordt. Actievere vormen zoals het hengelen met de werphengel met kunstaas op roofvis bieden een goed alternatief om het probleem van de fysieke inactiviteit aan te pakken, rustigere vormen zoals het hengelen met de vaste hengel echter niet. Belangrijk is wel om in het achterhoofd te houden dat het niet zo is

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The goal of this thesis was to show the potential of continuously monitoring mental workload and recovery to improve the working conditions of truck drivers. For this purpose, 19 truck drivers were monitored. By using Mindstretch’s algorithms, their mental workload and recovery could be determined. In the first part of the data analysis, the main energy drainer and recovering activities were defined, and a recommendation plan was proposed. The most recovering activity was ‘resting’, during which 69% of the drivers showed more recovery than mental workload. The most demanding activity was ‘uncoupling’, of which the effort-recovery score was lower than -20 for 55% of the drivers, indicating high mental demand. Although there were these general trends, it turned out that the energy drainer and recovering activities were individually different (SDaverage=14.90). Concrete examples were used to show how a recommendation plan can be made, with both the individual and group perspectives providing useful insights. To advocate the usefulness of mental state management, the relation between driver’s performance and mental state was assessed. In 25%/75% of the cases, a negative/no correlation was found between overload and performance. Underload was negatively/not/positively correlated to performance for 17%/76%/7% of the cases. On average, models, with overload and/or underload as independent variables, were able to explain 15%, 15%, 10% and 3% of the variance in braking hard, accelerating hard, speeding offences and fuel efficiency. These results show overload/underload having a relatively small negative impact on performance. Furthermore, in a second analysis on six drivers, it was found that in 13% of the cases, the effect of overload on performance was influenced by how mentally demanding the recent past had been. In two-thirds of these cases, it was seen that the effect reduced if the recent past was less demanding, advocating the importance of a balanced mental workload to prevent not being able to cope with overload. The effect of mental state on performance seems small. However, improving performance with a few percentages by good mental state management could significantly save costs for trucking companies over time. Although the results are not entirely conclusive, this thesis has shown the potential of monitoring mental workload and recovery in a real-life work environment. Future research could leverage the insights provided to make an even more convincing argument.

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Despite the significant advances in tissue engineering (TE) research there is still a very limited number of regularly used clinical applications in this area. One of the reasons for this difficult transition is the lack of consistent product quality caused by inadequately controlled production systems. This thesis was performed within the scope of an interdisciplinary research program on bone TE which aims at developing and quantitatively evaluating clinically relevant osteoinductive TE constructs. Within this context a model-based feedback control strategy was proposed for perfusion bioreactors. This strategy was based on (i) using control inputs (like flow rate or oxygen concentration) to create a well defined micro-environment, (ii) on-line measurements of the cell response to its process environment and (iii) data-based mechanistic models of the input/output relation which could be used to continuously adjust the control inputs of the bioreactor in such a way that the output reaches the desired value. The aim of this thesis was to develop the tools which make such process control possible for bone TE.In the light of this aim, a 2D+ perfusion bioreactor concept was developed, which allows to use microscopic imaging of cells in a 3D-like environment. This bioreactor system was validated for human periosteum derived cells (hPDCs) on a titanium scaffold made with additive manufacturing. Next, a combination of experiments and modelling was used to quantify the fluid flow environment in this 2D+ scaffold during perfusion. Subsequently, an image processing algorithm was developed to quantify cell number and cell distribution. This algorithm could be used for images of the 2D+ scaffolds, but also for other typical TE scaffolds, like hydro gels and 3D titanium scaffolds.These tools (2D+ bioreactor, fluid flow quantification and image based cell counting) were used together to study the effect of fluid flow induced shear stress on hPDCs cultured on 2D+ titanium scaffolds. Finally, a data-based modelling approach was used to characterize the dynamic response (change in outlet oxygen concentration) of a bioreactor to changes in flow rate and inlet oxygen concentration.In conclusion, during this work several innovative tools were developed and validated to study the concepts of process control for bone TE bioreactors. It shows how quantification of the micro-environment and the local cell response can lead to a better insight in the complex process of 3D cell culture. In a next step, the knowledge and methods developed in this thesis can be used to design model-based feedback control strategies for perfusion bioreactors.

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According to numerous reports, driver drowsiness in one of the leading causes of traffic accidents. Nowadays, various drowsiness detection methods have been developed based on behavioural, vehicular and physiological features. In this master’s thesis, the use of physiological changes related to thermoregulation is tested for driver drowsiness detection. During an 80-minute monotonous driving task, the core body temperature (CBT) and two distal-to-proximal skin temperature gradients (DPG) were monitored. The DPG1 was obtained by subtracting the forehead temperature (proximal region) from the middle finger temperature (distal region), the DPG2 by subtracting the forehead temperature from the wrist temperature (distal region). Due to missing data and indistinct drowsiness levels, only 23 out of 30 completed driving simulations were available for analysis. On average, an increase in both DPG’s and a delayed decrease in CBT was observed in the drowsy drivers. Similar but less pronounced trends were observed in the non-drowsy drivers. However, due to the large variation in data between subjects within the drowsy and non-drowsy population, only the difference in increase in DPG2 between both groups was proved to be statistically significant. Next, univariate decision trees based on the CBT, DPG1 and DPG2 resulted in an accuracy of 65.2%, 73.9% and 78.3%, respectively. After validation, these were 30.4%, 73.9% and 69.6%. Combining the information of all three body temperature variables resulted in an accuracy of 87.0%, meaning that 20 out of 23 drivers were correctly classified as “drowsy” or “non-drowsy”. After validation, the accuracy was reduced to 65.2%. Additionally, since each subject had completed the driving simulation once in the afternoon and another time in the evening, it was shown that for only 3 out of 15 participants there was a significant difference in sleepiness scores given during the afternoon test and those given during the evening test. Therefore, no clear dominant effect of the circadian pacemaker or of the homeostatic hourglass mechanism on the drowsiness level was found. Finally, the disadvantage of using driver drowsiness detection based on vehicular features was demonstrated as the expected deterioration in driving behaviour of the drowsy drivers only became apparent at the end of the driving task or when it came to the total number of road edge excursions. Apart from these incidental analyses, the main conclusion of this master’s thesis is that physiological changes related to thermoregulation offer potential for use in driver drowsiness detection systems.