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Who is 'smarter', humans or buildings?: A mixed method assessment of occupant behavior in smart building environments.
No full textGiven the building sector's significant impact on energy consumption and CO2 emissions, there is a clear need for a sustainable solution. Here, smart building technologies are emerging as a promising response, as they offer the potential to improve operational efficiency while reducing environmental impact. However, the development of smart building solutions for the building sector often follows a technology-driven approach, in which technical feasibility and overall system optimization are prioritized over occupants’ perspectives, preferences, and behavior. As a result, building systems and technologies are not fully aligned with how occupants use and interact with these spaces. Bridging the gap between theoretical knowledge and practical application is, therefore, crucial for unlocking the full potential of smart building technology. This study focused on enhancing our understanding of the interaction between smart building technology and users. A specific focus is placed on climate control technology within the broader landscape of smart building systems. By employing an exploratory approach, in which a combination of qualitative and quantitative methods was utilized, smart building users’ preferences and behavioral mechanisms were explored. Through semi-structured interviews with smart building occupants, the study delved deeper into understanding the motivations, barriers, and other aspects of occupant behavior and interactions with smart building technology. Additionally, insights from interviews with industry experts provided valuable perspectives on which key factors contribute to the increased adoption of smart building technology. These qualitative findings were complemented by quantitative data collected through an online survey (n=92), which allowed trends and preferences to be identified from a larger group of smart building occupants. The study showed that the successful implementation of smart building technology goes beyond mere technological details. It provided empirical insights into the preferences and behavioral mechanisms of smart building occupants, filling a gap in the existing literature. By exploring these aspects, the research deepened our understanding of user interactions within smart buildings. Consequently, it advocates for a user-centered approach to smart building initiatives, emphasizing the importance of understanding human preferences and incorporating user feedback to effectively adapt technology to their specific needs and routines. However, the study revealed a diverse range of user preferences and motivations regarding interaction with smart building technology, including preferences regarding control levels, system feedback, transparency, flexibility, and interface design. This diversity highlighted the absence of a one-size-fits-all approach to implementing smart building technology. Consequently, specific practical recommendations were developed to guide stakeholders in smart building initiatives, emphasizing a more user-centered implementation that ensures adaptability to the unique needs and preferences of building users.Complex Systems Engineering and Management (CoSEM
Reassessing tin circularity and criticality
No full textTin is an important metal for society with a high risk of supply disruptions. It is, therefore, classified as a critical material in many parts of the world. An exception is the European Union, for which tin was classified as a non-critical material in 2023. However, there are many discrepancies in the literature regarding the definitions and values of the indicators used to determine tin criticality in general, and recycling indicators in particular. Values for end-of-life recycling rate (EoL RR) range between 20% and 75%, and values for end-of-life recycling input rate (EoL RIR) range between 11% and 32%. In this paper, we critically assess the circularity and criticality indicator values for tin and calculate new values using material flow analysis. The new values for tin recycling indicators are lower than those used in most previous research, with a global EoL RR of 16% and an EoL RIR of 11% in 2017. Based on the updated recycling values, combined with a highly concentrated supply, high import reliance, and difficult substitution, we argue that the European Union should classify tin as a critical material. This reclassification can lead to more policy attention for tin, which can help reduce the impact of future supply disruptions and increase the resilience of the European and global tin supply chains.Policy AnalysisDesign for Sustainabilit
A combined experimental and computational approach to unravel degradation mechanisms in electrochemical wastewater treatment
No full textElectrochemical wastewater treatment is a promising technique to remove recalcitrant pollutants from wastewater. However, the complexity of elucidating the underlying degradation mechanisms hinders its optimisation not only from a techno-economic perspective, as it is desirable to maximise removal efficiencies at low energy and chemical requirements, but also in environmental terms, as the generation of toxic by-products is an ongoing challenge. In this work, we propose a novel combined experimental and computational approach to (i) estimate the contribution of radical and non-radical mechanisms as well as their synergistic effects during electrochemical oxidation and (ii) identify the optimal conditions that promote specific degradation pathways. As a case study, the distribution of the degradation mechanisms involved in the removal of benzoic acid (BA) via boron-doped diamond (BDD) anodes was elucidated and analysed as a function of several operating parameters, i.e., the initial sulfate and nitrate content of the wastewater and the current applied. Subsequently, a multivariate optimisation study was conducted, where the influence of the electrode nature was investigated for two commercial BDD electrodes and a customised silver-decorated BDD electrode. Optimal conditions were identified for each degradation mechanism as well as for the overall BA degradation rate constant. BDD selection was found to be the most influential factor favouring any mechanism (i.e., 52-85% contribution), given that properties such as its boron doping and the presence of electrodeposited silver could dramatically affect the reactions taking place. In particular, decorating the BDD surface with silver microparticles significantly enhanced BA degradation via sulfate radicals, whereas direct oxidation, reactive oxygen species and radical synergistic effects were promoted when using a commercial BDD material with higher boron content and on a silicon substrate. Consequently, by simplifying the identification and quantification of underlying mechanisms, our approach facilitates the elucidation of the most suitable degradation route for a given electrochemical wastewater treatment together with its optimal operating conditions.Micro and Nano Engineerin
Integrated phononic waveguides in diamond
No full textEfficient generation, guiding, and detection of phonons, or mechanical vibrations, are of interest in various fields, including radio-frequency communication, sensing, and quantum information. Diamond is a useful platform for phononics because of the presence of strain-sensitive spin qubits, and its high Young's modulus, which allows for low-loss gigahertz devices. We demonstrate a diamond phononic waveguide platform for generating, guiding, and detecting gigahertz-frequency surface acoustic wave (SAW) phonons. We generate SAWs using interdigital transducers integrated on AlN/diamond and observe SAW transmission at 4-5 GHz through both ridge and suspended waveguides, with wavelength-scale cross sections (approximately 1 m2) to maximize spin-phonon interaction. This work is a crucial step for developing acoustic components for quantum phononic circuits with strain-sensitive color centers in diamond.QID/Taminiau LabCommunication QuTec
Buffer scheduling for improving on-time performance and connectivity with a multi-objective simulation–optimization model: A proof of concept for the airline industry
No full textSchedule design in the transportation and logistics sector is a widely studied problem. Transport service providers, such as the train industry and aviation, aim for schedules to be on-time according to the planning (i.e., on-time performance or OTP) in order to increase the service level by ensuring that passengers actually make their connections and to reduce costs. Transportation services also aim for schedules that serve a high variety of destinations and frequency of connections (i.e., connectivity). OTP and connectivity are both highly dependent on buffer time: more lucrative connections can often be offered by reducing the buffer time in the schedule, while more delay can be absorbed by more buffer time. Given strict constraints on the minimum turnaround time of aircraft and minimum (and maximum acceptable) transfer times of passengers, assigning buffer time in an already tightly planned schedule to optimize OTP and connectivity simultaneously is a big challenge. This research presents a novel multi-objective formulation of a daily flight schedule where buffer scheduling is used to ensure the optimal balance between OTP of the schedule and the passenger connections as connectivity, given the tight restrictions. This problem formulation is solved using a simulation–optimization framework. Specifically, we use the Multi-Objective Evolutionary Algorithm (MOEA) BORG. As a proof of concept, a daily European flight schedule of a large international airline is optimized on both OTP and connectivity. The results demonstrate that the presented multi-objective formulation and associated solving through simulation–optimization can result in candidate schedules with both better on-time performance and a higher connectivity.Policy AnalysisSystem Engineerin
Predicting Haemodynamic Instability in Critical Congenital Heart Disease Patients: A Proof of Concept
No full textIntroductionApproximately 9 in 1000 children are born with congenital heart disease (CHD), of whom a quarter are classified as critical CHD (CCHD) and require an intervention within their first year. Monitoring these patients in the Paediatric Intensive Care Unit (PICU) is crucial, yet with increasing amounts of data, detecting subtle changes that are important for the disease progression interpretation of all vital signs becomes difficult, even for skilled physicians. Machine learning (ML) offers potential solutions, however, challenges such as inter-patient variability and the absence of clear definitions for haemodynamic instability persist. This study aims to develop a ML algorithm for early prediction of haemodynamic instability in CCHD patients with high frequency vital-signs, addressing these challenges through objective labelling methods and stratification approaches.MethodsTwo approaches, on population and patient level, were developed with nested cross-validation (CV). Due to a high inter-patient variability, the patient specific approach was added. A first iteration of objectively labelling haemodynamic instability was proposed, based on medical interventions such as medication administration and fluid therapy. Since it is difficult to retrospectively determine for how long patients were unstable, multiple values for instability duration (dT ) were added to the analysis. To capture the temporal dependency of time-series data, lag-analysis was performed, adding the relation between the vital signs and their previous values to the model development. Lag-analysis included a sliding window that moved over the data. The width of sliding window (W ) was optimised during the model development. Additionally, a horizon (r ) was implemented, so the data within the sliding window were predicting future timestamps.ResultsThis retrospective study included a total of 224 admissions in the analysis. Two random forest classifiers were trained using a nested CV structure to detect haemodynamic instability in CCHD patients. For both approaches the same temporal settings (W : 50 minutes, r : 45 minutes, dT: 120 minutes) were used. This study has shown that the between-patient approach had notable differences between the mean train (85%, AUCPR) and test performance (40%, AUCPR). The in-patient approach, while using 20% and 10% of the test data for training, still yielded a test performance of 96% (AUCPR) and 90% (AUCPR), respectively. Discussion and conclusion Generally speaking, the experiments suggest that the first iterations of the models were not robust and generalised poorly. It is most likely caused by a large inter-patient variability and a simple labelling system that is still depending on subjectivity. This study has shown that the proposed prediction model, which combines high frequency vital signs, labels, and temporal settings (W, r, dT ), requires additional refinement before it can be considered clinically feasible to implement this model as a reliable bedside tool for predicting haemodynamic instability.TM30004; 35 ECTSTechnical Medicin
Exploring the barriers to collaboration between the domains Branding, Communications and Technology at Total Design
No full textThis report describes the graduation project in collaboration with Total Design (TD), a creative agency specialised in Branding, Communications and Technology. The primary objective of this thesis is to enhance the internal collaboration between these three domains. To achieve this goal, the study explores the barriers to collaboration, using co-creation sessions with TD employees as a key method to gather insights. The process follows a general approach consisting of four phases, Exploring the Current Context, Reframing the Problem, Creating Opportunities to Improve Collaboration and Catalyse Synergy Creation at TD, each described in its dedicated chapter. Leveraging co-creation sessions and interviews with employees of TD, the study shows that the internal team’s focus is seen as the main barrier to multidisciplinary collaboration within TD. This focus stems from team-specific targets, that discourage collaborative efforts between teams and cause each team to prioritise their own proposition to clients. As a result, clients are unaware of other services offered by TD and employees under-utilise the expertise of their colleagues. This internal team focus comes from TD’s existing organisational structure. Therefore, a new organisational structure is proposed as the final solution for TD. The proposed organisational structure introduces dynamic, project-based teams that replace traditional, static teams, facilitating fluid cross-domain collaboration and enabling a more agile response to client needs. The expected positive impact of the final design for clients is a broader service offering and improved client satisfaction, and enhanced learning and innovation for employees of TD.The report concludes with recommendations for the adoption of the new structure and recommendations for future work. The first aim to mitigate the reorganisation’s potential challenges, like coordination & communication and a loss of team identity and include involving employees for successful implementation. The latter suggested areas for further research, including broadening the focus group, incorporating diverse research methodologies and conducting follow-up studies to assess the impact of the changes implemented. The findings provide valuable insights into employees’ perception of the current situation, the barriers to collaboration and the desire for engaging employees in decision making. To align with employee demands and enhance multidisciplinary collaboration, TD is recommended to transition towards the proposed organisational structure that facilitates dynamic project team configurations.Strategic Product Desig
The Value of Travel Distance in Tourism travelling by Air: A Stated Choice Experiment
No full textTourists travelling by airplane contribute significantly to the CO2 emissions. The number of flights covering longer distances is rising and, consequently, implies more energy consumption. This leads to a greater environmental impact compared to flights covering shorter distances. Although people are expected to continue travelling, adjusting the holiday destinations and modes of transport can effectively reduce the environmental footprint of tourism, all while maintaining pleasurable travel experiences. To minimize CO2 emissions by adjusting holiday destinations, destinations closer to home should be chosen. A trade-off seems to appear when selecting a holiday destination, involving a balance between the attractiveness of a specific destination and the different travel-related considerations. More attractive destinations can be reached with increasing distances, yet this also increases travel time and cost which are both preferred to be minimized. So far, research into the value of distance in this trade-off in the context of holiday destination choices is found to be limited. Therefore, this research studies how people value distance, controlling for travel time and travel cost, when choosing the destination for their holiday to gain a more comprehensive understanding of tourism travel behaviour. Since long-distance flights have larger CO2 emissions compared to flying over shorter distances, this study compares distances for holiday destinations that require long-distance flights with flights covering shorter distances. Additionally, these results can lead to interesting insights for policymakers. The main research question examined in this study is:‘What is the value of physical distance for Dutch tourists in the choice of their summer holiday destination?’For this study, a stated preference survey was created to collect data for addressing the research question, resulting in a sample of 254 Dutch tourists. To understand if distance holds intrinsic value, once controlling for travel time and for travel cost, and to investigate if the value of distance would change when travel time and cost are considered, two versions of a stated choice experiment are included in the survey. The respondents are randomly assigned to one of the choice experiments, resulting in half of the respondents completing one version while the other half completing the other.Since people prefer different types of holidays, including all attractiveness attributes in choice sets may lead to many immediate ’no-go’ options. Therefore, the survey started with an additional experiment for all respondents. In this experiment, the respondents rated the attractiveness of different holiday destinations on a 10-point rating scale. A regression model was estimated based on the observed ratings. This gives an indication of the attractiveness of holiday destinations. To investigate the intrinsic value of distance and if the value of distance changes considering travel time and cost, the results of the two versions of the choice experiments are estimated with a Multinomial Logit model. When comparing the results of both versions it was found that in version Choice experiment presenting all attributes a very small positive value exists, so small that it can be negligible. This suggests that once controlling for travel time and costs, there is no intrinsic value in distance. This was unexpected as it was expected that further distances would have a positive influence on the utility...Engineering and Policy Analysi
Adsorption characteristics and mechanisms of water-soluble polymers (PVP and PEG) on kaolin and montmorillonite minerals
No full textThe excessive use and accumulation of water-soluble polymers (WSPs, known as “liquid plastics”) in the environment can pose potential risks to both ecosystems and human health, but the environmental fate of WSPs remains unclear. Here, the adsorption behavior of WSPs with different molecular weight on kaolinite (Kaol) and montmorillonite (Mt) were examined. The results showed that the adsorption of PEG and PVP on minerals were controlled by hydrogen bond and van der Waals force. The Fourier transform infrared (FTIR) spectra and two-dimensional correlation spectroscopy (2D-COS) analysis revealed that there were interactions between the Al-O and Si-O groups of the minerals and the polar O- or N-containing functional groups as well as the alkyl groups of PEG and PVP. The adsorption characteristics of WSPs were closely related to their molecular weight and the pore size of minerals. Due to the relatively large mesopore size of Kaol, both PEG and PVP were absorbed into inner spaces, for which the adsorption capacity increased with molecular weight of the polymers. For Mt, all types of PEG could enter its micropores, while PVP with larger molecular weights appeared to be confined externally, leading to a decrease in the adsorption capacity of PVP with increasing molecular weight. The findings of this study provide a theoretical basis for scientific evaluation of environmental processes of WSPs.Sanitary Engineerin
Experimental study on drag coefficient of flexible vegetation under non-breaking waves
No full textLaboratory experiments of wave propagation over rigid and flexible vegetation fields, with the same configurations, were conducted to understand the effect of vegetation flexibility on the drag coefficient (CD). The direct method and the least squares method (LSM), based on force and flow measurements, are applied to calculate the CD in the experimental conditions. The formulations of both methods are extended to estimate the CD for flexible vegetation cases. A video analysis was performed to account for the swaying motion. Typically, wave dissipation is lower for flexible than for rigid vegetation of the same configuration, under the same flow condition. Therefore, a proportional effect in the corresponding CD results, obtained from common CD calibration to wave dissipation without considering vegetation motion, is usually observed. However, the present results show that although the wave dissipation was 34% lower for flexible relative to rigid vegetation, the respective CD values were close. CD estimations considering vegetation motion and inertia suggest that CD of flexible vegetation was up to 13% higher relative to rigid vegetation. Accounting for inertia reduced the CD for rigid vegetation up to 7%, while raised the CD for flexible vegetation up to 13%.Environmental Fluid Mechanic