20005 research outputs found
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Screening of the regulations and legislations that control the chemical content of plastics through their lifecycle
No full textThe mechanical recycling of plastic waste plays a crucial role in advancing the circular economy, ensuring that valuable resources within the waste stream are preserved for extended periods. However, the sustainable, economic, and environmentally responsible management of plastic waste remains a significant challenge, particularly when plastics are sourced from contaminated streams, such as those originating from electronic waste (e-plastics). These materials often contain a wide range of chemical substances, some of which can pose considerable environmental and health risks. Therefore, assessing the degree of contamination in plastic waste is essential to ensure a safe and sustainable life cycle for plastics. Regulatory frameworks aim to address this issue by establishing guidelines and limitations on the use of hazardous chemicals, as well as providing standards for the proper treatment of contaminated waste streams. This paper offers a comprehensive review of the regulations and legislation governing the chemical content of plastics throughout their life cycle—spanning from production to waste disposal and recycling. The objective is to deepen the understanding of the challenges and limitations associated with the recycling of e-plastics and to highlight the importance of these regulatory measures in achieving sustainable plastic waste management
A concise mathematical description of active inference in discrete time
No full textIn this paper we present a concise mathematical description of active inference in discrete time. The main part of the paper serves as a basic introduction to the topic, including a detailed example of the action selection mechanism. The appendix discusses the more subtle mathematical details, targeting readers who have already studied the active inference literature but struggle to make sense of the mathematical details and derivations. Throughout, we emphasize precise and standard mathematical notation, ensuring consistency with existing texts and linking all equations to widely used references on active inference. Additionally, we provide Python code that implements the action selection and learning mechanisms described in this paper and is compatible with pymdp environments
Design guidelines for material extrusion of metals (MEX/M)
No full textThis study introduced a systematic framework to develop practical design guidelines specifically for filament-based material extrusion of metals (MEX/M), an additive manufacturing (AM) process defined by ISO/ASTM 52900. MEX/M provides a cost-efficient alternative to conventional manufacturing methods, which is particularly valuable for rapid prototyping. Although AM offers significant design flexibility, the MEX/M process imposes distinct geometric and process constraints requiring targeted optimization. The research formulates and validates design guidelines tailored for the MEX/M using an austenitic steel 316L (1.4404) alloy filament. The feedstock consists of a uniform blend of 316L stainless steel powder and polymeric binder embedded within a thermoplastic matrix, extruded and deposited layer by layer. Benchmark parts were fabricated to examine geometric feasibility, such as minimum printable wall thickness, feature inclination angles, borehole precision, overhang stability, and achievable resolution of horizontal and vertical gaps. After fabrication, the as-built (green-state) components undergo a two-step thermal post-processing treatment involving binder removal (debinding), followed by sintering at elevated temperatures to reach densification. Geometric accuracy was quantitatively assessed through a 3D scan by comparing the manufactured parts to their original CAD models, allowing the identification of deformation patterns and shrinkage rates. Finally, the practical utility of the developed guidelines was demonstrated by successfully manufacturing an impeller designed according to the established geometric constraints. These design guidelines apply specifically to the machine and filament type utilized in this study
Spektrum : das Magazin der Technischen Universität Hamburg (TUHH), Ausgabe 01/2025
No full textTECHNOLOGIE: Ethik und KI zusammen denken; NACHHALTIGKEIT: Mit Recycling-Beton neu bauen; ECIU UNIVERSITY: Europaweit gemeinsam lerne
Klimaschutz im internationalen Luftverkehr: Szenarien zur Erreichung der THG‑Emissionsminderungsziele
No full textSeparation and quantification of damage-induced and non-damage-induced vibro-acoustic modulation and the problem of contrary modulations
No full textVibro-acoustic modulation (VAM) has been exploited over the last three decades to assess and monitor the integrity of structures. One major challenge is the separation of damage-induced and non-damage-induced modulation in the measured system response for reliable structural health monitoring (SHM). Most scientific works on VAM imply that the initiation and growth of structural damage is expected to cause modulation that adds up with non-damage-induced modulation increasing the total amount of modulation. This article unfolds why this assumption can be invalid for standard VAM applications: It is explained analytically why two nonlinearities working in opposite directions (one stiffening the structure under loading, one softening it) cause contrary modulations: The two nonlinear contributions can neutralize each other in the system response. Numerical simulations are then presented that investigate separately one damage-induced nonlinearity and two non-damage-induced nonlinearities in the same aluminum plate. The modulation caused by them individually is quantified and the subsequent comparison demonstrates the occurrence of contrary modulations in this representative VAM setup. It has to be concluded that damage-induced modulation does not necessarily increase the total modulation in the system response. This finding has potential to boost VAM-related research regarding its reliability and sensitivity
Simulation-based characterization of alginate aerogel packed bed compaction via DEM-BPM
No full textThe global demand for aerogels is constantly growing, thus, optimizing and scaling up the production processes
have become increasingly important in the last decade. The utilization of millimeter-sized aerogel particles for
such purposes is typically preferred due to inherent advantages in handling and production compared to other
geometries. The production of these particles is most commonly accomplished using a particle packed bed
(autoclave). This process presents, however, several challenges, including the impact of mechanical loads on the
quality of the product. Therefore, this work focuses on deepening the understanding of mechanical properties
and deformation mechanisms of aerogel particles in packed beds under uniaxial compaction. The investigated
alginate aerogel particles are characterized by a spherical shape (circularity of 0.96), a specific surface area of
~352 m2/g, an average diameter of ~3.3 mm, and a bulk density of ~0.05 g/cm3. In addition, this study extends
a DEM-BPM model to capture the mechanical deformation of biopolymer aerogels, both as individual particles
and within packed beds. The simulations were calibrated and validated using experimental data from uniaxial
compaction tests. An optimization methodology was implemented to reduce reliance on traditional trial-and-
error methods and improve the model’s accuracy. The results demonstrate that the proposed DEM-BPM model
effectively replicates the mechanical behavior of alginate aerogels, showing strong agreement between experi-
mental data and minimal deviations for both single particles and packed beds (R2≥ 0.93). This model serves as a
promising tool for gaining deeper insights into the mechanical properties of aerogels and improving production efficiency.
Additionally, the DEM-BPM model can be expanded to incorporate intermediate products, such as
hydrogels and alcogels, enabling process optimization at every stage of aerogel manufacturing
New type of process control system for bioprocesses with model-assisted optimization tools
No full textDie Entwicklung effektiver Regelungs- und Prozessführungsstrategien für Bioprozesse stellt Ingenieure vor große Herausforderungen. Bioreaktorsysteme müssen selbstständig wechselnde Bedingungen steuern – eine Aufgabe, die innovative Automatisierungswerkzeuge wie das Prozessleit- und Simulationssystem WinErs erfordert. Dieses integriert komplexe Prozessmodelle, ermöglicht Simulationen sowie Parameterschätzungen und bietet Regelungsstrategien für Prozesse mit multiplen Ein- und Ausgängen. Der WinErs-Data Lake sammelt umfangreiche Prozessdaten, während modellassistierte Werkzeuge die Optimierung von Steuervariablen unterstützen. Es bietet eine effektive Lösung, um die Lücke zwischen Labor und Industrie zu schließen.The development of effective control strategies for bioprocesses faces engineers with major challenges. Bioreactor systems must independently control changing conditions – a task that requires innovative automation tools such as the WinErs process control and simulation system. This integrates complex process models, enables simulations and parameter estimations, and offers control strategies for processes with multiple inputs and outputs. The WinErs Data Lake collects extensive process data, while model-assisted tools support the optimization of control variables. It provides an effective solution to bridge the gap between laboratory and industry
Unlinkable data sharing with dynamic access control
No full textIn an increasingly information-driven society, the volume of digital footprints left by individuals has surged significantly. Safeguarding the anonymity of data generated by computing devices is becoming more challenging as these offer deep insights into personal behaviors. We propose a user-centric and privacy-preserving data space for unlinkable data sharing based on a central intermediary. By integrating differential privacy techniques with fine-grained access control, our system allows data providers to store their data confidentially and unlinkable at the intermediary. Data consumers can then locate and request data via this intermediary, ensuring that data providers remain informed without revealing the origin of the data. Additionally, the intermediary facilitates continuous data sharing, requiring only a single data upload. Our approach is designed to protect data providers from both external and internal attackers, as well as from an honest-but-curious intermediary
Quantum algorithm for the advection-diffusion equation by direct block encoding of the time-marching operator
No full textA quantum algorithm for simulating multidimensional scalar transport problems using a time-marching strategy is presented. A direct unitary block encoding of the explicit time-marching operator is constructed, resulting in the intrinsic success probability of the squared solution norm without the need for amplitude amplification, thereby retaining a linear dependence on the simulation time. The algorithm separates the explicit time-marching operator into an advection-like component and a corrective shift operator. The advection-like
component is mapped to a Hamiltonian simulation and combined with the shift operator through the linear combination of unitaries algorithm. State-vector simulations of a scalar transported in a steady two-dimensional Taylor-Green vortex support the theoretical findings