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Effect of delayed inhibitor supply on AA2024-T3 intermetallic activity: A local in situ analysis with reflected microscopy
No full textUnderstanding how late an inhibitor can be released once corrosion initiated without compromising corrosion protection may help in developing more efficient anticorrosion coatings. We explored this idea through time-controlled Ce(NO3)3 availability to AA2024-T3 immersed in 0.05 M NaCl. Ce(NO3)3 was supplied at 0, 30, 60, and 180 s from the start of immersion to get a concentration of 0.001 M. Detailed visualization of surface changes at the intermetallic particle level was obtained using in-situ reflected microscopy. SEM-EDX and confocal laser microscopy confirmed the extent of intermetallic degradation and local inhibitor deposition corresponding to operando changes. When the inhibitor is supplied within 60 s of immersion, the surface changes slowdown earlier and are visually less extensive than in uninhibited systems. Furthermore, our results highlight the potential of reflected microscopy for local corrosion inhibition studies and underscore the importance of understanding the interaction between inhibitor release timing and corrosion protection.Group Garcia EspallargasTeam Arjan Mo
Opportunities of Natural Resources Making Buildings More Resilient
No full textAn overview is given of the state-of-the-art of natural and hybrid ventilation in buildings in general. The focus of this paper is on boundary conditions for openable windows. As a case study the Co Creation Centre at the TU-Delft is discussed. Occupants live in their own houses and often in an office or other working environments as well. Due to the development of working on a distance, accelerated by the COVID-pandemics, they generally have more choice which environment is the best. That is why a holistic approach is necessary for buildings in general and houses. Natural ventilation offers a wide range of low-cost opportunities to realize the required thermal comfort and need of fresh air. Boundary conditions for ventilation are the limitation of cooling and heating by intelligent building physical design of the façade or roof, with better balancing heat loss due to transmission and heat gain by solar access. In this field there is still a lack of knowledge at many professionals. In most cases natural ventilation has to be supported by robust mechanical systems. Effective integration is a rather new field of research, learning from the past. Current examples of integration are discussed, in which BMS-systems play a key role.Environmental & Climate Desig
Improving global digital elevation models using space-borne GEDI and ICESat-2 LiDAR altimetry data
No full textOpen source Global Digital Elevation Models (GDEMs) serve as an important base for studies in geosciences. However, these models contain vertical errors due to various reasons. In this study, data from two Satellite LiDAR altimetry systems, GEDI and ICESat-2, were used to improve the vertical accuracy of GDEMs. Three different machine learning methods, namely an Artificial Neural Network (ANN), Extreme Gradient Boosting (XGBoost), and a Convolutional Neural Network (CNN), were employed to improve existing DEM data with satellite LiDAR data. The methodology was tested in five areas with varying characteristics. Ground control data were selected from high accuracy DEMs generated from Airborne LiDAR and GNSS data. The use of ANN method improved the vertical accuracy of SRTM data from 6.45 to 3.72 m in Test area-4. Similarly, the CNN method demonstrated an improvement in the vertical accuracy of bare ground SRTM data increasing from 3.4 to 0.6 m in Test area-4. In Test area-5, the ANN method improved the vertical accuracy of SRTM data with slopes between 30 and 60%, increasing from 3.8 to 0.5 m. Notably, the results underscore the successful improvement of GDEMs across all test areas.Optical and Laser Remote Sensin
Zn induced surface modification of stable goethite nanoparticles for improved regenerative phosphate adsorption
No full textIron oxide-based adsorbents showed potential to reach ultra-low phosphorus (P) concentrations to prevent eutrophication and recover P. High affinity, high capacity at low P concentrations (<1 mg L−1), good stability, and reusability of the adsorbent are key factors for economic viability. In this study, nanoparticles of goethite (α-FeOOH), a highly stable phase, have been synthesized with increasing Zn2+-doping, 0–20 %at. Zn/Fe, to manipulate the surface properties, following the results of a previous work. Mössbauer spectroscopy showed preserved goethite phase and increased point of zero charge (pzc) at low Zn-doping percentages, while at higher percentages (>5%at.) co-existing phases with increased specific surface area formed. Low concentrations (0.1–10 mg L−1) batch adsorption tests showed increased P removal per unit mass with increasing doping. However, the highest pzc, affinity and P removal per unit area were observed for the 5%at. doped sample, suggesting this dopant concentration to provide the most effective surface. A regeneration test, performed at a lower pH than usual, showed preserved, even improved P desorption with increasing doping. Mössbauer spectroscopy showed that the nanoparticle phase and composition, up to 5%at., doping was preserved throughout the process. These results are promising to develop a stable effective Zn-doped goethite-based adsorbent for P recovery at ultra-low concentrations.RST/Fundamental Aspects of Materials and EnergyBT/Environmental BiotechnologyRID/TS/Instrumenten groe
Geometric effects on impact mitigation in architected auxetic metamaterials
No full textLightweight materials used for impact mitigation must be able to resist impact and absorb the maximum amount of energy from the impactor. Auxetic materials have the potential to achieve high resistance by drawing material into the impact zone and providing higher indentation and shear resistance. However, these materials must be artificially designed, and the large deformation dynamic effects of the created structures must be taken into consideration when deciding on a protection concept. Despite their promise, little attention has been given to understanding the working mechanisms of high-rate and finite deformation effects of architected auxetic lattice structures. This study compares the static and dynamic elastic properties of different auxetic structures with a honeycomb structure, a typical non-auxetic lattice, at equivalent mass and stiffness levels. In this study, we limit the investigation to elastic material behavior and do not consider contact between the beams of the lattices. It is demonstrated that the equivalent static and dynamic properties of individual lattices at an undeformed state are insufficient to explain the variations observed in impact situations. In particular, the initial Poisson's ratio does not determine the ability of a structure to resist impact. To gain a thorough comprehension of the overall behavior of these structures during localized, high rate compression, the evolution of the elastic tangent properties under compression and shear deformation was monitored, leading to a more profound understanding. Observations made in one configuration of stiffness and mass are replicated and analyzed in related configurations.Applied Mechanic
Changing hearts instead of changing minds – another take on climate action
No full textThis piece elaborates on a ‘new way of thinking’ (Einstein, 1946) that would contribute to overcoming the challenge of climate change and its impacts. This ‘new way’ will have us go beyond using facts and figures alone to persuade and cajole. It will have us stretching our moral imagination (Johnson, 2016) and empathising with people very different from ourselves. It will have us investing in processes of exchange which support the co-creation of knowledge and the future we want together.Policy Analysi
A generating absorbing boundary condition for simulating wave interaction with maritime structures in current or at forward speed
No full textThe lack of suitable boundary conditions in practical surface wave simulations with maritime structures in current or at forward speed may cause energy in the computational domain to accumulate due to spurious wave reflection. The common way to prevent wave reflection is to use passive wave absorbers, such as damping zones or relaxation zones, which requires larger domains at the cost of computational effort. Our goal is to derive a local generating absorbing boundary condition (GABC) for long-crested irregular waves on top of a mean flow, using the flow to model the forward speed of a structure such as a ship. Earlier work has demonstrated that a local GABC for free surface waves has a performance similar to passive wave absorbers, but at a reduced computational effort. New in the present work is that we extend, verify and validate the GABC in the presence of a nonzero mean flow. The GABC is designed to be accurate for a range of wave components in irregular sea states, with the resulting reflection coefficients for each component lower than a chosen value, say 5%. Having used potential flow theory for its derivation means that the boundary should not be placed at the exact location where wave breaking is expected, such as very close to the structure in the domain, or in the surf zone in coastal modeling. For the application with ships in this article that does not pose a limitation. The performance is demonstrated for a range of dimensionless wave number between 0 and 6. Such a boundary condition is obtained through a rational approximation of the linear dispersion relation with a mean flow, in combination with vertical derivatives of the solution variables along the boundary. Local linearization means that the GABC incorrectly considers bound, nonlinear wave components to be freely propagating wave components. Bound components, however, tend to have smaller amplitudes and do not appear to affect performance for the considered cases. Results of simulations with regular and irregular waves, on top of flows with different magnitudes and directions, are found to agree with the theory. The main source of differences is the implementation of the second derivate in the GABC near the free surface. Simulations of a Wigley hull at forward speed in irregular waves are compared to an experiment that was conducted specifically for validating the ABC. The data of the experiment are available as open data through doi: 10.4121/21320604. The comparison between simulation and experiment demonstrates that the GABC with a mean flow can be applied not only for theoretical simulations with propagating waves, but also for more practical applications with a structure in the domain.Ship Hydromechanics and Structure
Exploring beliefs and perceptions towards Advanced Rider Assistance Systems (ARAS) in motorcycle safety
No full textThe study applied the Theory of Planned Behaviour (TPB) to explore motorcycle riders’ underlying behavioural, normative, and control beliefs towards Advanced Rider Assistance Systems (ARAS). Each belief was explored in terms of three categories of technologies, (i) advanced technologies that help riders manage riding according to situations and conditions, (ii) advanced technologies that help riders to stop, and (iii) advanced technologies that help riders to corner. Eight focus groups were conducted with 39 motorcycle riders (Mage = 44.54 years, 27 males) who resided in Australia. First, participants completed a short online questionnaire which asked demographic information (e.g., age, gender, riding experience), before taking part in a 50-minute semi-structured online focus group. Participants’ knowledge of ARAS differed depending on the type of technology, with most participants reporting good to excellent knowledge of cruise control and standard anti-lock braking system (ABS) and a poor to fair understanding of selectable riding modes and cornering ABS. For behavioural beliefs, two common advantages reported for all three categories of technologies were safety and that the technologies would benefit new riders or riders with less experience. The three common disadvantages included concerns over riders’ reliance on the technologies, cost, and loss of skill or false sense of security. For normative beliefs, participants reported that their loved ones (i.e., partner, family, and friends) would approve of them using these technologies, with participants perceiving that ‘purists’ (i.e., riders who prefer to ride traditional motorcycles) would disapprove. For control beliefs, cost, lack of information on the safety of advanced technologies, and not being able to switch off systems were reported as barriers to use. Lowering insurance premiums, education/test rides, technologies as selectable options, and availability, were all identified as factors that would encourage use of ARAS. By providing information about ARAS, riders will become more informed about ARAS, which may enhance trust and user acceptance. Additionally, ongoing research and development are essential to ensure the evaluation and improvement of ARAS and mitigate any unintended consequences.Safety and Security Scienc
Wind Turbine Load Control and Estimation: Advancements by Coordinate Transformations
No full textWind energy has become one of the most economically attractive energy sources thanks to technological advances, such as wind turbine upscaling. To harness higher-quality wind reachable at greater heights, wind turbine towers are made taller; to increase power capture, rotors are made with wider diameters. Mass/material reduction for the manufacture of such components is thus imperative to keep large-scale turbines profitable, resulting in more flexible structures but exacerbating fatigue loading. Therefore, the reliance on advanced control methods is ever higher to mitigate multiple wind turbine structural loads while ensuring optimal power production.Advanced convex economic model predictive control (CEMPC) methods have garnered attention lately in the wind turbine control community. Such techniques possess several advantages apart from those inherent in being subsets of the model predictive control (MPC) family. First, it is capable of accounting for multiple economic objectives for wind turbines, such as power production optimization, fatigue load reduction, and excessive actuation limitation, in a straightforward and unified way. This also means that the trade-off calibration between the economic objectives (by weight tuning) can be done with ease. Additionally, the convexity of the underlying optimization control problem (OCP) guarantees that a globally optimal solution can be found with high numerical effectiveness, which may lead to real-time feasibility. This thesis, in particular, is focused on the development of a unified CEMPC framework, combining the potentials of two emerging CEMPCs in the wind turbine area, namely the power-and-energy CEMPC and the quasi-linear parameter-varying model predictive control (qLPV-MPC), for addressing multiple wind turbine structural loads.The former achieves its convexity by exchanging nominal wind turbine variables, such as blade pitch, generator torque, and rotational speed, with alternative variables in terms of aerodynamic and generator powers and rotor kinetic energy. This results in the OCP containing linear dynamics, convex constraints, and concave objectives to be maximized. Being originally focused on fulfilling power gradient requirements from a grid code, a fatigue load mitigation consideration was introduced later on for fore-aft tower motion in the literature. Unfortunately, little attention was paid to the mitigation of the more weakly-damped side-side tower loading, as well as blade fatigue loads.Such a knowledge gap is filled in this thesis; in particular, both key components' fatigue loads are mitigated by exploiting the individual blade pitching capabilities of the power-and-energy CEMPC framework. Since, in this framework, blade pitch actuation is achieved mainly by manipulating aerodynamic power inside the CEMPC, a redefinition of the latter is necessary to enable such a feature. To be precise, multiple aerodynamic powers, each representing that of a single blade, were employed as decision variables of the CEMPC instead of a single quantity. Further mapping of the aerodynamic powers into side-side blade forces, as well as augmentation of side-side tower dynamics into the CEMPC's internal model, enables counteractive control actions for reducing side-side tower load. Mapping the powers into blade and rotor moments enables alleviation of the blade loads.On the other hand, the utilization of qLPV-MPC for deploying a passive wind turbine tower resonance prevention by dynamically optimal frequency skipping has been gaining attention in the literature. For enabling active load cancelation in this framework, however, a periodic load estimation is needed. In this thesis, such an estimation scheme is developed, employing a Kalman filtering method. Aligned with the qLPV-MPC implementation for the aforementioned passive method, the internal model of the filter is rendered in a demodulated fashion by applying a model demodulation transformation (MDT) to an extended wind turbine side-side tower dynamics. Measurement signal demodulation (MSD) is utilized for capturing the slow-varying components of wind turbine tower measurements to be fed to the Kalman filter. The filter is thus capable of not only estimating the demodulated periodic load signals but also those of the unknown and unmeasured tower states with good agreement with the ground truth.The next challenge addressed in this thesis is the provision of an active control method specifically aimed at tackling the side-side periodic loading of the tower. A family of repetitive control methods, namely modulation\-/demodulation control (MDC), is adopted in this thesis to handle the cancellation of the periodic loading. In principle, MDC consists of output signal demodulation, projecting the frequency component of interest (namely the rotor frequency) in the signal into low-frequency quadrature and in-phase representations. On these axes, diagonal single-input, single-output (SISO) controllers can be designed, resulting in control signals, which, by a modulation process, are translated into a single control signal, being an additive generator torque signal, oscillating at the frequency of the disturbance and thereby canceling it. A phase offset, with its optimal value determined by the plant's phase at the disturbance frequency, is needed and included in the modulation. This results in the full decoupling of the control channels, as well as the correction of an occurring gain sign flip due to the varying excitation frequency, which could have deteriorated the controller's performance and induced instabilities. The MDC extends a conventional tower damper controller specifically aimed at mitigating the tower loading at its natural frequency. As a result, both the tower load components at the natural frequency and the rotor frequency are mitigated simultaneously.This thesis has, thus, highlighted the significant role various coordinate transformations play in advancing state-of-the-art wind turbine control, be it a transformation of signals into a different set of variables in power and energy terms or into different time scales. The former has enabled the formulation of power-and-energy CEMPC for side-side tower load and blade loads mitigation, extending this framework's fatigue load mitigation capabilities. The latter transformation, demonstrated by the MDT, paves the way for estimating unknown and unmeasurable periodic load and tower states in a demodulated manner, essential in activating the periodic load cancelation feature of the novel qLPV-MPC method. The MDC method has successfully enabled active side-side periodic tower load cancelation by leveraging a modulation-demodulation scheme, another way of transforming coordinates into different time scales where convenient yet effective control system design can be made. This thesis has, therefore, provided elements required for constructing a unified CEMPC framework, where the benefits of the said coordinate transformations may be further harnessed.Team Jan-Willem van Wingerde
Conversational AI in the context of setting up a project brief: Creating a conversational AI tool for self-evaluating and improving the quality of inter-organisational design briefings.
No full textThe In-House Creative Studio faces a significant challenge due to an increasing workload among its team of creatives, which includes visual designers, concept creators, copywriters, producers, photographers, and project/event managers. This team may only experience slight expansion, despite the growing demand for campaign and event materials targeted at three main groups: B2B, B2C, and Talent. Consequently, the Creative Studio is forced to be selective, unable to approve all project requests due to the overwhelming volume of work. Ideally, the studio would like to take on more projects. However, the creative team's efficiency is frequently undermined by the considerable time spent managing internal stakeholders, the misalignment resulting from unclear communications, and inefficient workflows. The primary source of these issues was identified as stakeholders providing incomplete or illogical design briefs.This graduation project explores how Conversational AI might be used in the context of setting up inter-organisational project briefs to help briefing writers improve their design briefings.Explorative research on the challenges within creative corperate processes and GenAI opportunities clarified that design briefings are a major bottle neck within creative corporate processesRecognizing this, it becomes evident that to effectively address this bottleneck, stakeholders need assistance in improving the quality of their design breifings prior to the meeting and without external help from the Creative Studio’s briefings reviewers. This resulted in creating an conversational agent that enabled stakeholders to self-evaluate and improve the quality of their v1 briefings without external help before the first briefing meeting with the Creative Studio. The final design was evaluated over the span of two sessions with an internal stakeholder of the case company and the Creative Strategist. In the first session, Jelly’s ability to assist the briefing writer was evaluated. In the subsequent session, the feedback comments of Jelly were compared to that of the Creative Strategist. The results suggest that while Jelly has been effective in certain areas, such as providing detailed feedback that aligns with feedback standards of the briefing reviewers, it requires refinements in user interface language, feedback customisation, and context-specific content generation. The feedback from Jelly, when accurate, led to noticeable improvements in the quality of v1 briefings, aligning with the goals of enabling the stakeholder to self-evaluate their briefings independently. The findings suggest that Jelly was found to be capable in offering valuable feedback that improved the quality of the briefing. This thesis concludes with critical reflections to anticipate the future of GenAI in creative corperate processes. The first anticipation includes proposing a new relationship between GenAI and human creatives in the form of co-performance; where one fulfills a role, the other enhances its performance. The second anticipation states that large e-commerce organisation would have terms in their employee contracts that would consider personalised chatbots created by them as intellectual property of the company. In other words, in such organisations, personalised chatbots would likely be developed through a centralised approach. Ultimately, the design contributes to the field of conversational AI design approaches in the context of corperate creative processes by providing a practical and reproducible example. Design for Interactio
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