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Enhancing the durability of Pt nanoparticles for water electrolysis using ultrathin SiO2 layers
No full textExtending the lifetime of electrocatalytic materials is a major challenge in electrocatalysis. Here, we employ atomic layer deposition (ALD) to coat the surface of carbon black supported platinum nanoparticles (Pt/CB) with an ultra-thin layer of silicon dioxide (SiO2) to prevent deactivation of the catalyst during H2 evolution. Our results show that after an accelerated durability test (ADT) the current density at −0.2 V vs. reversible hydrogen electrode (RHE) of the unprotected Pt/CB catalyst was reduced by 34%. By contrast, after coating the Pt/CB catalyst with 2 SiO2 ALD cycles, the current density at the same potential was reduced by 7% after the ADT procedure, whereas when the Pt/CB sample was coated with 5 SiO2 ALD cycles, the current density was reduced by only 2% after the ADT. Characterization of the Pt particles after electrochemical testing shows that the average particle size of the uncoated Pt/CB catalyst increases by roughly 16% after the ADT, whereas it only increases by 3% for the Pt/CB catalyst coated with 5 cycles of SiO2 ALD. In addition, the coating also strongly reduces the detachment of Pt nanoparticles, as shown by a strong decrease in the Pt concentration in the electrolyte after the ADT. However, 20 cycles of SiO2 ALD coating results in an over-thick coating that has an inhibitory effect on the catalytic activity. In summary, we demonstrate that only a few cycles of SiO2 ALD can strongly improve the stability of Pt catalyst for the hydrogen evolution reaction.ChemE/Product and Process EngineeringLarge Scale Energy Storag
Timber terraced housing: Assessment of transverse stability
No full textThe transverse stability of timber terraced houses can be provided by CLT stability walls where decoupled timber terraced houses are preferred to meet acoustic requirements leading to rather large thicknesses for the CLT stability walls and many large connections for anchorage to the foundation. The main goal of this research was to investigate the transverse stability behaviour of timber terraced houses, using a case study provided by WSP. Models to assess the transverse stability of timber terraced houses are simple schematizations with hand calculations of the decoupled and coupled timber terraced houses and FE models of decoupled timber terraced houses with and without T-section and coupled timber terraced houses with and without T-section. The coupling of the houses can be achieved by 4 Straviwood Modulink 6.0 kN connections per floor level. The T-section can be realised with double screws with diameter 𝑑 = 12 𝑚𝑚 with a spacing of 𝑠 = 100 𝑚𝑚.Simple schematizations with hand calculations of the decoupled and coupled timber terraced houses result in overdimensioning of the connections since bending of the floors due to deformation of the stability wall, providing resistance to the deformation of the stability wall, is not considered. This resulted in 6 hold downs per CLT stability wall.Compared to the FE model of decoupled timber terraced houses without T-section, all FE models have a positive influence on the design of connections in terms of reduction of number of hold downs and improvement of the total tension support reaction. Coupling of the houses is better compared to application of a T-section for decoupled houses. An improvement of the total tension support reaction of 83% and 67% for respectively the house on the left and the house on the right, compared to the decoupled timber terraced houses without T-section, can be achieved by coupled timber terraced houses with T-section. This also resulted in a reduction of 5 hold downs per CLT stability wall and the possibility to reduce the thickness of the CLT stability wall. Civil Engineering | Structural Engineerin
River plastic transport affected by tidal dynamics
No full textPlastic is an emerging pollutant, and the quantities in rivers and oceans are expected to increase. Rivers are assumed to transport land-based plastic into the ocean, and the fluvial and marine transport processes have been relatively well studied to date. However, the processes controlling the transport in tidal rivers and estuaries, the interface between fluvial and marine systems, remain largely unresolved. For this reason, current estimates of riverine plastic pollution and export into the ocean remain highly uncertain. Hydrodynamics in tidal rivers and estuaries are influenced by tides and freshwater discharge. As a consequence, flow velocity direction and magnitude can change diurnally. In turn, this impacts the transport dynamics of solutes and pollutants, including plastics. Plastic transport dynamics in tidal rivers and estuaries remain understudied, yet the available observations suggest that plastics can be retained here for long time periods, especially during periods of low net discharge. Additional factors such as riparian vegetation and riverbank characteristics, in combination with bi-directional flows and varying water levels, can lead to an even higher likelihood of long-term retention. Here, we provide a first observation-based estimate of net plastic transport on a daily timescale in tidal rivers. For this purpose, we developed a simple Eulerian approach using sub-hourly observations of plastic transport and discharge during full tidal cycles. We applied our method to the highly polluted Saigon River, Vietnam, throughout six full tidal cycles in May 2022. We show that the net plastic transport is about 20%-33% of the total plastic transport. We found that plastic transport and river discharge are positively and significantly correlated (Pearson's R2Combining double low line0.76). The net transport of plastic is higher than the net discharge (20%-33% and 16%, respectively), suggesting that plastic transport is governed by factors other than water flow. Such factors include wind, varying plastic concentrations in the water, and entrapment of plastics downstream of the measurement site. The plastic net transport rates alternate between positive (seaward) net transport and negative (landward) net transport as a result of the diurnal inequality in the tidal cycles. We found that soft and neutrally buoyant items had considerably lower net transport rates than rigid and highly buoyant items (10%-16% vs. 30%-38%), suggesting that transport dynamics strongly depend on item characteristics. Our results demonstrate the crucial role of tidal dynamics and bi-directional flows in plastic transport dynamics. With this paper we emphasize the importance of understanding fundamental transport dynamics in tidal rivers and estuaries to ultimately reduce the uncertainties of plastic emission estimates into the ocean.Water Resource
Understanding influences on entrepreneurship educator role identity
No full textPurpose: Despite the considerable increase in research on entrepreneurship education, few studies examine the role of entrepreneurship educators. Similarly, most frameworks from entrepreneurship education recognize the educator’s importance in facilitating instruction and assessment, but the factors influencing the educator role are not well understood. According to the identity theory, personal factors including self-efficacy, job satisfaction and personal values influence the perspective of self, significance and anticipations that an individual in this role associates with it, determining their planning and actions. The stronger the role identity the more likely entrepreneurship educators will be in effectively developing their entrepreneurial skills as well as the overall learning experience of their students. The objective of this study is to pinpoint the factors that affect entrepreneurial role identity. Design/methodology/approach: Drawing upon the identity theory, this study developed a theoretical framework and carried out an empirical investigation involving a survey of 289 entrepreneurship educators across the globe. Structural equation modeling (SEM) technique was applied to analyze and explore the factors that impact the identity of the educators in their role as entrepreneurship teachers. Findings: The findings show that the role identity of entrepreneurship educators is significantly influenced by their self-efficacy, job satisfaction and personal values. Among these factors, self-efficacy and job satisfaction have the most significant impacts on how educators perceive their role. The implications of these results and directions for future research are also discussed. Originality/value: The novelty of the current study is derived from its conceptualization of the antecedents of role perception among entrepreneurship educators. This study stands out as one of the earliest attempts to investigate the factors that shape an individual’s scene of self and professional identity as an entrepreneurship educator. The significance of comprehending the antecedents of role perception lies in the insights it can offer into how educators undertake and execute their role, and consequently, their effectiveness in teaching entrepreneurship.Responsible Marketing and Consumer Behavio
Classifying Human Manual Control Behavior Using LSTM Recurrent Neural Networks
No full textThis article discusses a long short-term memory (LSTM) recurrent neural network that uses raw time-domain data obtained in compensatory tracking tasks as input features for classifying (the adaptation of) human manual control with single- and double-integrator controlled element dynamics. Data from two different experiments were used to train and validate the LSTM classifier, including investigating effects of several key data preprocessing settings. The model correctly classifies human control behavior (cross-experiment validation accuracy 96%) using short 1.6-s data windows. To achieve this accuracy, it is found crucial to scale/standardize the input feature data and use a combination of input signals that includes the tracking error and human control output. A possible online application of the classifier was tested on data from a third experiment with time-varying and slightly different controlled element dynamics. The results show that the LSTM classification is still successful, which makes it a promising online technique to rapidly detect adaptations in human control behavior.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
Multi-criteria Analysis of Sustainable Aviation Fuel Technologies: Integrating Environmental, Economic, Social, and Technical Criteria along with Stakeholder Perspectives to Compare Fast Pyrolysis, Hydrothermal Liquefaction, and HEFA Pathways
No full textThe aviation sector, responsible for approximately 2% of global anthropogenic greenhouse gas emissions, is projected to grow 4-6 times by 2050, conflicting with the European Union’s Green Deal target of achieving net-zero emissions by the same year. While aircraft electrification offers a promising solution, its application is largely limited to short-haul flights due to range and weight limitations. Sustainable Aviation Fuel (SAF) emerges as a compelling alternative for long-haul operations, as it is compatible with both existing infrastructure and can be blended with fossil fuels. Currently, Hydroprocessed Esters and Fatty Acids (HEFA) is the predominant pathway for producing SAF. There remains a significant supply gap for SAF, emphasising the need to scale up production and explore alternative technologies. This thesis evaluates the potential of hydrothermal liquefaction (HTL) and fast pyrolysis (FP) to address this supply gap.The research objective is to compare HTL and FP with HEFA. A literature review identified three main knowledge gaps: (1) a lack of studies on the social impacts of HTL and FP, (2) the absence of stakeholder involvement in evaluating these technologies, and (3) the need for updated data integration to effectively compare HTL and FP with established SAF technologies like HEFA. This study addresses these gaps using a multi-criteria analysis (MCA) to provide a holistic evaluation across a multi-temporal timescale while considering diverse stakeholder perspectives.The study employed a four-phase methodology. The first phase began with the identification of stakeholders through desk research. The second phase involved establishing the criteria for the MCA via a literature review focusing on four main dimensions: environmental (Global Warming Potential and use of by-products), economic (capital expenditure, operating expenditure, and feedstock price), technical (technology readiness level and efficiency), and social (safety and social impacts related to feedstock use). The stakeholders assigned the weightings of each criterion relative to the others during structured interviews using the Best-Worst Method (BWM). In the third phase, each technology was assessed against the established criteria through detailed analysis using specific methods. Based on the findings of the analysis, SAF experts assigned performance scores to each technology per criterion. Finally, in the fourth phase, the criteria and their weightings, along with the performance scores, were integrated to calculate a final weighted MCA score for each technology. This resulted in a final ranking of the technologies based on their overall MCA scores for each stakeholder.HTL and FP are potential alternatives to the HEFA pathway to produce SAF, each with different advantages and disadvantages. Technically and economically, HEFA currently outperforms due to its maturity and lower costs. At the same time, HTL and FP offer potential environmental and social benefits, particularly in terms of the kind of feedstocks used and the possibilities of by-product valorisation. The preference for each technology varies between stakeholders, indicating the need for a balanced approach that integrates multiple perspectives in SAF implementation decision-making. This research provides actionable insights for advancing SAF technologies and supports the broader goal of achieving sustainable aviation.Complex Systems Engineering and Management (CoSEM
Human‑centric computational urban design: Optimizing high‑density urban areas to enhance human subjective well‑being
No full textUrban areas face increasing pressure due to densification, presenting numerous challenges involving various stakeholders. The impact of densification on human well-being in existing urban areas can be both positive and negative, which requires a comprehensive understanding of its consequences. Computational Urban Design (CUD) emerges as a valuable tool in this context, offering rapid generation and evaluation of design solutions, although it currently lacks consideration for human perception in urban areas. This research addresses the challenge of incorporating human perception into computational urban design in the context of urban densification, and therefore demonstrates a complete process. Using Place Pulse 2.0 data and multinomial logit models, the study first quantifies the relationship between volumetric built elements and human perception (beauty, liveliness, and safety). The findings are then integrated into a Grasshopper-based CUD tool, enabling the optimization of parametric designs based on human perception criteria. The results show the potential of this approach. Finally, future research and development ideas are suggested based on the experiences and insights derived from this study.Urban Data Scienc
Agile Space-Observation Satellite Task Scheduling Optimisation
No full textThe congestion of orbits around the Earth, particularly in Low Earth Orbit (LEO), necessitates the implementation of space-based Space Situational Awareness (SSA) missions. This increasing orbital congestion, driven by the proliferation of mega constellations, poses significant challenges to satellite operations and collision avoidance. In response, commercial entities are beginning to plan and launch space-based SSA missions. Despite this emerging interest, there is a notable gap in the literature regarding the scheduling of operations for these missions, which are characterised by the inclusion of multiple operational modes.Additionally, existing literature on operational scheduling often lacks high-fidelity modelling of onboard resource dynamics. This research addresses this gap by focusing on energy-constrained scenarios, developing novel operational scheduling frameworks suitable for assigning data collection and data downlink tasks for optical space-based SSA missions under such constraints.To enhance the fidelity of the scheduling process, this research employs both low-fidelity and high-fidelity simulators to model the dynamic behaviour of onboard resources. The developed frameworks are tested in various scenarios to validate their practicality and effectiveness. A significant contribution of this research is the open-source availability of part of the developed scheduling frameworks, utilising software accessible under the TU Delft license. This open-source approach ensures that the research can be extended and built upon by future researchers, fostering ongoing advancements in the field of space-based SSA operations.Aerospace Engineerin
Electronic properties and collision cross sections of AgOkHm± (k, m = 1–4) aerosol ionic clusters
No full textExperimental evidence shows that hydroxylated metal ions are often produced during cluster synthesis by atmospheric pressure spark ablation. In this work, we predict the ground state equilibrium structures of AgOkHm± clusters (k and m = 1–4), which are readily produced when spark ablating Ag, using the coupled cluster with singles and doubles (CCSD) method. The stabilization energy of these clusters is calculated with respect to the dissociation channel having the lowest energy, by accounting perturbative triples corrections to the CCSD method. The interatomic interactions in each of the systems have been investigated using the frontier molecular orbital (FMO), natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) methods. Many of the ground states of these ionic clusters are found to be stable, corroborating experimental observations. We find that clusters having singlet spin states are more stable in terms of dissociation than the clusters that have doublet or triplet spin states. Our calculations also indicate a strong affinity of the ionic and neutral Ag atom towards water and hydroxyl radicals or ions. Many 3-center, 4-electron (3c/4e) hyperbonds giving rise to more than one resonance structure are identified primarily for the anionic clusters. The QTAIM analysis shows that the O–H and O–Ag bonds in the clusters of both polarities are respectively covalent and ionic. The FMO analysis indicates that the anionic clusters are more reactive than the cationic ones. Using the cluster structures predicted by the CCSD method, we calculate the collision cross sections of the AgOkHm± family, with k and m ranging from 1 to 4, by the trajectory method. In turn, we predict the electrical mobilities of these clusters when suspended in helium at atmospheric pressure and compare them with experimental measurements.ChemE/Materials for Energy Conversion and StorageAtmospheric Remote Sensin
Temperature effects on fatigue delamination behavior in thermoset composite laminates
No full textTemperature can significantly affect fatigue delamination growth (FDG) behavior in composites, while fiber bridging has been frequently reported during FDG. The focus of this study was therefore on investigating temperature effects on FDG behavior with fiber bridging. Mode I fatigue delamination experiments were conducted on a thermoset composite laminates M30SC/DT120 at different temperatures. The Paris relation and fatigue resistance curve (i.e. fatigue R-curve) were used to interpret bridging effects on FDG behavior and to explore temperature effects on fiber bridging development. A modified Paris relation was employed to determine the effects of temperature on the intrinsic FDG behavior at the crack front excluding fiber bridging. The Paris interpretations clearly demonstrate that fiber bridging can significantly retard FDG behavior at different temperatures. Temperature can have different effects on fiber bridging development and the intrinsic FDG behavior. Particularly, elevated temperature can promote more bridging fibers, whereas decreased temperature has negligible influence on fiber bridging. When looking at the intrinsic delamination resistance, mode I FDG can accelerate at elevated temperature but decrease at freezing temperature. Fractographic examinations indicate that fiber/matrix interface debonding is the dominant damage mechanism in mode I FDG at different temperatures. Elevated temperature can lead to the weakening of interface adhesion, contributing to faster intrinsic mode I FDG behavior and more fiber bridging development. And a semi-empirical fatigue model based on normalization was finally proposed to determine mode I intrinsic FDG behavior at different temperatures for engineering applications.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & CompositesGroup Alderlieste