Delft University of Technology

Energy-efficient wastewater treatment plants (WWTPs) utilize systems like high-rate activated sludge (A-stage) system to redirect organics from wastewater are redirected into energy-rich sludge (A-sludge). Anaerobic membrane bioreactors (AnMBRs) offer lower footprint and higher effluent quality compared to conventional digesters. In this study, the biological treatment and the filtration performances of AnMBRs for A-sludge digestion under mesophilic and thermophilic conditions were comparatively evaluated through lab-scale experiments, mass balancing and dynamic modeling. Under thermophilic conditions, a higher COD fraction of the influent sludge was converted into methane gas than under mesophilic conditions (65% versus 57%). The energy balance indicated that the surplus energy recovery under thermophilic conditions was less than the additional energy required for heating the AnMBR, resulting in a more than three-fold higher net energy recovery under mesophilic conditions. Therefore, operating an AnMBR for sludge digestion under mesophilic conditions has a higher potential to improve the energy balance in WWTPs.

The development of advanced ship positioning and intelligent sensing technologies has transformed navigation at sea, moving beyond reliance on captains’ experience and standard routes. The trajectories traversed by ships at sea contain valuable data that can be mined to map maritime transportation networks and inform intelligent navigation systems. Ship trajectory data at scale enables discovery of the underlying network of maritime routes, providing key insights for applications like intelligent navigation, abnormal behavior detection, trajectory prediction, and maritime traffic pattern analysis. This study reviews the development of research on maritime route networks (MRNs) derived from ship trajectory data. It summarizes the technical process to construct a MRN, contrasting approaches for identifying waypoints, extracting routes, and representing the overall maritime traffic network structure. Finally, this study explores potential applications of MRNs and anticipates promising future research directions in this domain.

This chapter builds upon the concept of sparse controllability and presents three related notions of controllability under input sparsity constraints:stabilizability, output controllability, and nonnegative controllability. We present three main results. We first prove that sparse stabilizability is equivalent to standard stabilizability. Next, we show that if a linear dynamical system is output controllable, there exist upper and lower bounds on the minimum sparsity level required to ensure sparse output controllability. Finally, we establish that a linear dynamical system is sparse nonnegative controllable if and only if it is both nonnegative controllable and sparse controllable.

Linear dynamical systems are widely used models in various control applications, and the control theory for linear systems is a well-studied field. However, many systems face constraints due to limited resources or underlying physical factors, which can be effectively modeled using the concept of sparsity. This chapter introduces the idea of sparsity in linear dynamical systems, highlights its significance across several applications, and provides an overview of the book’s content.

In this chapter, we estimate the sparse initial state of a linear dynamical system from its observations when the inputs are known. We formulate this as a sparse vector recovery problem, a topic well-studied in the signal processing field of compressed sensing. We present several sparsity-aware algorithms from the compressed sensing literature to address this problem, including popular methods such as convex relaxation-based basis pursuit, greedy algorithms like orthogonal matching pursuit and compressive sampling matching pursuit, as well as thresholding techniques, such as iterative hard thresholding, hard thresholding pursuit, and sparse Bayesian learning.

Distillation is widely used for fluid separation in chemical industries, but accounts for a half of the operational costs and 40-50% of the energy usage due to its low energy efficiency. Process intensification could effectively enhance the energy efficiency as well as improve the economic performance of distillation processes by integrating unit operations or functions. However, matching suitable intensified distillation techniques systematically with given separation tasks remains a challenge. This study is the first to generate a conceptual multi-step selection and decision approach by first going through several high level questions with corresponding suggested solutions for a separation task, then identifying the process bottlenecks and intensification targets via a list of evaluation criteria. Each of the technologies goes through a pre-filled process intensification (PI) matrix, and the most promising intensified technologies are recommended, and potential solutions are compared against the task specifications. The PI matrix proposed in this work yields a short list of appropriate solutions to be designed and economically assessed, proposing a screening framework for fluid separations in order to make a rapid selection at an early stage. Several binary, ternary, and multicomponent zeotropic and azeotropic mixture separations are carried out as case studies to illustrate the application of the proposed methodology, being validated using literature data. The proposed methodology can also help reduce the search space before carrying out rigorous optimization for the synthesis and design of the distillation.

Cutting-edge photonic devices frequently rely on microparticle components to focus and manipulate light. Conventional methods used to produce these microparticle components frequently offer limited control of their structural properties or require low-throughput nanofabrication of more complex structures. Here, we employ a synthetic biology approach to produce environmentally friendly, living microlenses with tunable structural properties. We engineered Escherichia coli bacteria to display the silica biomineralization enzyme silicatein from aquatic sea sponges. Our silicatein-expressing bacteria can self-assemble a shell of polysilicate “bioglass” around themselves. Remarkably, the polysilicate-encapsulated bacteria can focus light into intense nanojets that are nearly an order of magnitude brighter than unmodified bacteria. Polysilicate-encapsulated bacteria are metabolically active for up to 4 mo, potentially allowing them to sense and respond to stimuli over time. Our data demonstrate that synthetic biology offers a pathway for producing inexpensive and durable photonic components that exhibit unique optical properties.

Direct interactions between quantum particles naturally fall off with distance. However, future quantum computing architectures are likely to require interaction mechanisms between qubits across a range of length scales. In this work, we demonstrate a coherent interaction between two semiconductor spin qubits 250 μm apart using a superconducting resonator. This separation is several orders of magnitude larger than for the commonly used direct interaction mechanisms in this platform. We operate the system in a regime in which the resonator mediates a spin–spin coupling through virtual photons. We report the anti-phase oscillations of the populations of the two spins with controllable frequency. The observations are consistent with iSWAP oscillations of the spin qubits, and suggest that entangling operations are possible in 10 ns. These results hold promise for scalable networks of spin qubit modules on a chip.

Drug transport from blood to extravascular tissue can locally be achieved by increasing the vascular permeability through ultrasound‐activated microbubbles. However, the mechanism remains unknown, including whether short and long cycles of ultrasound induce the same onset rate, spatial distribution, and amount of vascular permeability increase. Accurate models are necessary for insights into the mechanism so a microvessel‐on‐a‐chip is developed with a membrane‐free extravascular space. Using these microvessels‐on‐a‐chip, distinct differences between 2 MHz ultrasound treatments are shown with 10 or 1000 cycles. The onset rate is slower for 10 than 1000 cycles, while both cycle lengths increase the permeability in spot‐wise patterns without affecting microvessel viability. Significantly less vascular permeability increase and sonoporation are induced for 10 versus 1000 cycles at 750 kPa (i.e., the highest studied peak negative acoustic pressure (PNP)). The PNP threshold for vascular permeability increases is 750 versus 550 kPa for 10 versus 1000 cycles, while this is 750 versus 220 kPa for sonoporation. Vascular permeability increases do not correlate with αvβ3‐targeted microbubble behavior, while sonoporation correlates with αvβ3‐targeted microbubble clustering. In conclusion, the further mechanistic unraveling of vascular permeability increase by ultrasound‐activated microbubbles in a developed microvessel‐on‐a‐chip model aids the safe and efficient development of microbubble‐mediated drug transport.

Data ecosystems are networks of autonomous actors who consume, produce, or provide data along with related resources such as software, services, and infrastructure. Public Data Ecosystems (PDE) and Open Data Ecosystems (ODE) are specific subtypes of data ecosystems. They have the potential to transform how governments use data, stimulate public sector innovation, and foster collaborative efforts to co-create smarter cities and societies. Public and open data ecosystems play a crucial role in supporting democratic societies by increasing government transparency, promoting citizen participation, and encouraging multi-stakeholder cooperation. Moreover, they significantly contribute to the achievement of the Sustainable Development Goals (SDGs) and alignment with principles of smart living. Public and open data ecosystems also support the vision of Society 5.0. To fulfill this potential, it is essential that public and open data ecosystems are not only established but also designed to be sustainable, resilient, equitable, and fair. However, achieving these goals is challenging, as public and open data ecosystems are complex phenomena that go beyond traditional definitions of data ecosystems. This Special Section emerged as a follow-up from the track ‘“Sustainable Public and Open Data Ecosystems” at the 25th Annual International Conference on Digital Government Research (dg.o 2024) and the track “Open Data” at the IFIP EGOV-CeDEM-EPART 2024. The interesting papers on public and open data ecosystems presented in the tracks of both conferences revealed a common interest in open platforms, where data providers and data users find each other and collaborate to co-create services and products that benefit society, where this collaboration is enabled by digital technologies. The presentations confirmed earlier claims, according to which the adoption and development of these ecosystems have been fragmented, lacking balance between data supply and demand, and often excluding specific user groups being linear and lacking skill-training, which reduces their value-generation and sustainability. It is where the idea of the Special Section emerged from, and three papers were selected for publication.

Both CH4 hydrate accumulation and hydrate-based CO2 sequestration involve hydrate formation in mixed clay sediments. The development of realistic clay models and a nanoscale understanding of hydrate formation in mixed clay sediments are crucial for energy recovery and carbon sequestration. Here, we propose a novel molecular model of pseudo-hexagonal montmorillonite nanoparticles. The stress–strain curves of tension, compression, and shear of pseudo-hexagonal montmorillonite nanoparticles exhibit linear characteristics, with tension, compression, and shear moduli of ∼435, 410, and 137 GPa, respectively. We perform microsecond molecular dynamics simulations to study CH4 and CH4/CO2 hydrate formation in montmorillonite–illite mixed clay sediments with surface defects. The results indicate that hydrate formation in mixed clay sediments is significantly influenced by the presence of clay defects. CH4 and CH4/CO2 mixed hydrates are challenging to form at the junction between the inside and outside clay defects. CH4 and CH4/CO2 mixed hydrates exhibit a preference for forming outside the clay defects rather than inside the clay defects. Some CH4 and CO2 molecules from the inside clay defect migrate to the outside clay defect, thereby promoting CH4 and CH4/CO2 mixed hydrate formation outside the clay defects. This molecular insight advances the development of clay particle models and expands an understanding of natural gas hydrate accumulation and hydrate-based CO2 sequestration.

Urban areas across the world are increasingly facing water scarcity due to population growth and urban expansion, which places significant stress on land use and leads to the depletion of water bodies. In many developing nations, the pursuit of economic gains often takes precedence over environmental concerns, resulting in unsustainable urban development. For rapidly expanding cities in these countries, sustainable urban water management is crucial to balancing economic development with environmental preservation. The concept of “water-sensitive cities” integrates environmental preservation, technological innovation, and community engagement to address these challenges. Urban ponds, especially in cities like India, play a crucial role in this context, providing environmental benefits as well as many ecosystem services. However, urbanization places significant stress on these ponds, causing pollution, deterioration, and disregard. This research conducted in Kozhikode, a fast-growing coastal city in India, aims to highlight the pivotal role of urban ponds in enhancing the city’s water sensitivity. The study encompasses comprehensive field surveys to identify and evaluate urban ponds, considering water quality, ecosystem services, and governance dynamics. The results of water quality show that most of the ponds have the potential to act as a decentralised drinking water supply source. The study also revealed the importance of ecosystem services provided by urban ponds, ranging from local benefits to global contributions. Multiple governance challenges for the conservation of urban ponds are also identified. The study highlights the significance of preserving urban ponds while advocating for enhanced management strategies through proper governance mechanisms. Proposed recommendations on governance include policy refinements, community engagement, pollution mitigation, and integrated planning approaches.

To boost the efficiency of perovskite solar cells beyond the limit of a single‐junction cell, tandem cells are employed, requiring low bandgap materials. This is realized by partially substituting lead(II) (Pb²⁺) with tin(II) (Sn²⁺) in the perovskite structure. In this work, a scalable method is presented to produce formamidinium lead tin iodide (FAPb0.5Sn0.5I3) films by sequential thermal evaporation (sTE) of PbSnI4, which is an alloy of SnI2 and PbI2, and FAI, in vacuum. Annealing at 200 °C yields a highly oriented and crystalline layer comprising grains over 1 µm on average. Photoconductance measurements reveal carrier lifetimes exceeding 2 µs and mobilities ≈100 cm²/(Vs). Structural analysis confirms that, while interdiffusion is abundant even at room temperature, the complete conversion requires high temperatures. Although the incorporation of Cs⁺ into the A‐site of the perovskite increases the grain size, charge carrier dynamics are reduced. A comparison between the sTE films and spin‐coated samples of the same composition demonstrates the superior photoconductance of the sTE films, without the need for any additives. Overall, this study showcases the potential of sTE for producing high‐quality low band gap (LBG) perovskite materials.

The built environment significantly contributes to current socioenvironmental crises, necessitating systemic change. Circularity and the commons are re-emerging as potential pathways for such transition. A circular built environment (CBE) aims to close resource loops, but its implementation is often slow and neglects social and local aspects. The commons framework emphasizes local involvement and sustainable self-management of shared resources. However, the intersection of circularity and the commons in spatial production is underexplored. This paper explores their relationship as “innate spatial tactics,” referring to the ways ordinary people interact with the built environment to meet their daily needs. Through a literature review, we developed a conceptual framework of “circular commoning,” encompassing three dimensions: resources, people, and governance. We applied this framework to analyze 16 empirical examples of circular commoning in contemporary urban settings. Our research shows that circularity and the commons are closely linked and mutually beneficial. Circular commoning involves diverse resources, changing social roles, and innovative governance. We identified three forms of circular commoning as innate spatial tactics: building circular, circular use of space, and creating spaces for circular activities. The framework developed here provides a basis for further action research. The practice review demonstrates that circular commoning is not only a distant utopian ideal but is enacted daily in diverse urban contexts. Such often-overlooked innate spatial tactics can offer valuable lessons for pathways toward a CBE involving principles of a circular society. Additionally, they can help shape new narratives and channel hope for practical progress towards circular futures.