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On resource efficient and individualized tree support structures for PBF-LB/M by process simulation
No full textLaser powder bed fusion of metals (PBF-LB/M) is a widely used additive manufacturing process known for its ability to create complex geometries with high precision. However, the necessity of support structures in PBF-LB/M leads to significant material and energy consumption, impacting overall efficiency. This work investigates a novel approach combining numerical process simulation with a user-friendly software tool to design resource-efficient tree support structures. A demonstrator part, manufactured from Ti6Al4V titanium ally, is used to validate the effectiveness of these generative support designs. The accuracy of the process simulation is assessed by comparing numerical results with geometrical deviations, obtained by 3D scanning the additively manufactured demonstrator parts. Additionally, the newly designed support structures are compared against widespread block supports, focusing on material consumption and geometrical precision. The demonstrator with tree supports shows 34.48 % less mean deviation than the one with block supports while being slightly lighter. These results demonstrate that the presented approach allows for the creation of individualized and efficient tree support structures, leading to faster print preparations, less misprints and therefore reduced manufacturing costs. Moreover, new manufacturing limits for thin rods in PBF-LB/M are identified by the successful fabrication of 50 mm long rods with minimum diameters of 0.3 mm and inclination angles to the built plate greater than 20 °, as well as vertical rods up to 300 mm in length. This increases the design freedom for components and support structures in PBF-LB/M processes drastically. Overall, the integration of advanced support design techniques shows promise for enhancing the sustainability and cost-effectiveness of PBF-LB/M
Adaptive On-the-fly Scan Method for Fast and Efficient Planar Near-field Acquisition
No full textRecent advancements in adaptive planar near-field scanning have enhanced the use of sparse measurement data for electromagnetic field (EMF) modeling and prediction. In this work, we propose an adaptive planar scanning solution that utilizes iterative row-by-row scans, where each row is scanned on-the-fly (OTF). Both the total number of rows and their separation are dynamically adjusted and optimized through correlation analysis of the values obtained from previous measurements. For initialization, a few evenly distributed row scans, typically 4-6 OTF scans, are performed, followed by an iterative process of finding new rows to scan using Gaussian Process Regression (GPR) based Bayesian optimization. For validation, both numerical and experimental examples, including wire and patch antenna arrays, are provided. Results show good performance of the proposed method, enabling rapid near-field acquisition within minutes, making it suitable for large-scale and high-resolution EMF scanning applications
An optical curvature sensor for tip position trajectory tracking control of soft robots
No full textAs soft robotics applications become more complex, control requirements increase. However, advanced control approaches require sensors which do not infer with the softness of the robot. In order to measure the current configuration of the robot, curvature measurements are of great importance, since bending is usually the main deformation of soft robots. This paper presents the design, fabrication, and trajectory tracking control of a novel low-cost fiber-optic soft curvature sensor that can measure the magnitude and direction of the curvature in two spatial directions. The curvature sensor can be seamlessly integrated into the silicone body of soft robots, preserving their inherent softness. The trajectory control of a beam-shaped soft robot is considered here as an example. For trajectory tracking control, an inverse kinematic feedforward controller combined with a simple feedback controller is investigated. Experiments show that the combined controller provides accurate trajectory tracking control with good disturbance rejection
Regression models for the prediction of the influence of magnesium ions on primary endothelial cell (HUVEC) proliferation and migration
No full textAngiogenesis is one of the first stages in fracture healing and bone repair. Therefore, numerous studies evaluating the effect of Mg as a promising degradable, metallic biomaterial on the proliferation and function of endothelial cells have been performed. However, these studies lack methodological homogeneity and therefore differ in fundamental conclusions. Here, Mg-concentration-, donor- and cell age- dependent relations to primary human umbilical cord vein endothelial cells (HUVEC) proliferation and migration were investigated systematically. The generated data were utilized to develop regression models in order to assess and predict the cell response on Mg exposition in a concentration range of 2–20 mM Mg in cell culture medium extract. A concentration of > 2 mM already induced a detrimental effect in the sensitive primary HUVECs. Molecular data quantifying angiogenesis markers supported this finding. An increased migration capacity has been observed at a concentration of 10 mM Mg. We compared linear regression, random forests, support vector machines, neural networks and large language models for the prediction of HUVEC proliferation for a number of scenarios. Using these machine learning methods, we were able to predict the proliferation of HUVECs for missing Mg concentrations and for missing passages with mean absolute errors below 10 % and as low as 8.5 %, respectively. Due to strong differences between the cell behaviour of different donors, information for missing donors can be predicted with mean absolute errors of 15.7 % only. Support vector machines with linear kernel performed best on the tested data, but large language models also showed promising results
Integration of the all-in-one electrode in an electrochemical flow cell for in situ hydrogen peroxide supply in hydroxylation mediated by immobilized unspecific peroxygenase
No full textHydrogen peroxide (H₂O₂) is a strong oxidizing agent that is commonly employed in chemical synthesis. Nevertheless, its utilization as a cosubstrate in biocatalytic reactions remains limited due to the deactivating effect on biocatalysts at an elevated concentration. An electrochemical synthesis of H₂O₂ represents an attractive approach, offering a controllable in situ generation of H₂O₂ without producing complex by-products. The objective of this study is to demonstrate the feasibility of the in situ electrogeneration of H₂O₂ using the All-in-One (AiO) electrode within a flow reactor technology. Integrating a bioelectrochemical system (BES) into a flow reactor technology, such as a flow cell, presents an alternative strategy for scale-up. In this study, the in situ generation of H₂O₂ is coupled with the hydroxylation of 4-ethylbenzoic acid catalyzed by the immobilized recombinant unspecific peroxygenase from Agrocybe aegerita (rAaeUPO) within a complete BES under batch and fed-batch operation modes. The electrochemical flow cell facilitates a controllable H₂O₂ generation by adjusting experimental parameters such as current density, aeration rate and residence time. The flow cell BES equipped with the AiO electrode yielded a catalytic productivity as high as 1.24 ± 0.02 mM h−1 (4.95 ± 0.1 g L−1 d−1), a total turnover number of rAaeUPO up to 3.38 · 105 ± 702 mol mol−1 and a turnover frequency up to 8.34 ± 0.14 s−1
Power-efficient control of non-linear magnetic field generators for MPI
No full textThe scaling of electrical power constitutes a significant challenge when adapting Magnetic Particle Imaging (MPI) to a human scale. The use of coils incorporating soft-iron cores serves to reduce power usage, but also introduces spatial imperfections and non-linearities in the current-to-field relationship. This study proposes methodologies for the control of the magnetic field output of a system comprising 18 coils, subject to the influence of saturated iron. In particular, we integrate current sequence optimization with neural network-based predictions for field and gradient values, thereby enabling the precise and power-optimal generation of magnetic fields. The proposed framework for controlling non-linear magnetic field generators represents a significant advancement in MPI technology, paving the way for the development of human-scale, power-efficient medical imaging solutions
Interactions and synergies between aircraft on-board systems and hydrogen turbofans
No full textThe intensive research currently being conducted on hydrogen-powered aircraft concepts poses several integrational challenges. Given that the hydrogen is stored in a liquid state on board the aircraft, a comprehensive analysis is necessary to determine the source of energy required to heat the hydrogen for direct combustion in turbofans. Since the engine itself poses a high-power heat source, it seems feasible that its waste heat may be used for hydrogen conditioning. This paper proposes three different hydrogen engine fuel heat management concepts. These comprise a finned flat tube heat exchanger at different positions within the core engine’s gas stream. A fourth option is presented, which postulates the use of hydrogen instead of fan air to cool customer bleed air. The concepts are evaluated at engine and at mission level, employing an enhanced engine resizing and heat exchanger conceptual design methodology. The results propose that in terms of thrust-specific energy consumption and mission block fuel mass, the intercooler concept is the favorable option. This is mainly attributed to a lower aircraft mass and lower air-side pressure losses compared to the other concepts subject to the study. In addition, the engine cycle efficiency benefits from intercooling the core airflow
Development and performance of Layer-by-Layer modified hollow fiber membranes as capillary nanofiltration
No full textThe need for alternative water sources due to water stress or changes in raw water qualities for use as drinking water often requires more advanced treatment techniques than currently in use. Thus, there is a demand for resource and energy efficient processes, with high process stability and reliability. Within this work the potential of Layer-by-Layer (LbL) modified hollow fiber ultrafiltration (UF) membranes was examined as one option in terms of ion rejection, rejection of dissolved organics, molecular weight cut-off (MWCO), fouling, and mechanical and process stability. Furthermore, a model was derived to differentiate between predominant polyelectrolyte (PE) build up during modification in terms of pore vs layer dominating PE multilayer formation. The results also identified the PE layering location as another crucial factor during membrane modification. Filtration in lab scale as well as pilot scale results in water works achieved high rejection rates for divalent ions (> 90 % for sulfate and magnesium, and > 80 % for calcium). However, some external parameters were investigated which influenced the resulting ion rejection. As shown in lab scale, high ionic strength in the feed solutions led to swelling of the PE structure, resulting in a change of separation characteristics. Nevertheless, swelling was highly dependent on the present type of ions and respective concentration. Model supported results clearly identified concentration polarization (CP) through the laminar boundary layer as dominating factor for the removal efficiency for sulfate as a model substance for divalent ions. Besides crossflow velocity and resulting laminar boundary layer thickness, model results showed a severe influence of CP dependent on membrane length. This underscores the importance of additional experiments beyond the lab to pilot scale on industrial length modules. Further investigations in lab scale showed that the modification of the membranes resulted in an MWCO in the lower range of NF membranes, providing high removal rates of dissolved organic substances. SAC254 removal rates of > 90% and TOC removal of > 80 % could be achieved even in Dead End operation for solutions containing natural organic matter (NOM). Fouling and removal rates were dependent on the NOM composition and their molecular weight distribution. Hereby, the solution containing a higher share of larger molecules reached higher rejection, while impact of fouling was lower. It is attributed to the deposition of foulants on top of the membrane surface instead of internally within the modified membrane structure. Membranes could successfully withstand the stress of hydraulic backwash (hydr. BW), though it was limited to a maximum hydr. BW flux of 50 L/(m² h). Combined with the good chemical stability, it would allow the implementation of a regular CEB, which was highly efficient for the removal of NOM foulants off the membrane surface. Overall, the LbL modification of hollow fiber UF membranes was successful on lab scale and on industrial scale membranes and could be operated successfully for several months in two different waterworks. The modified membranes combined exceptionally high NOM removal rates with the possibility for high divalent ion rejection and the stability of regular mechanical and chemical cleaning. Thus, LbL modified hollow fiber UF membranes did show a great potential for treatment of waters with high contents of dissolved organics and particle loads.Die Veränderungen der Wasserqualität von Rohwässern zur Trinkwassernutzung erzeugt eine Nachfrage nach ressourcen- und energieeffizienten Aufbereitungsmöglichkeiten, welche eine hohe Prozessstabilität und Qualitätssicherheit gewährleisten. Im Rahmen dieser Arbeit wurden Layer-by-Layer (LbL) modifizierte Hohlfaser-Ultrafiltrationsmembranen (UF) entwickelt. Weiterhin wurde das Potential der Membranen als mögliches Aufbereitungsverfahren in Bezug auf Ionenrückhalt, Rückhalt gelöster organischer Substanzen, Trenngrenze (MWCO), Fouling, sowie mechanischer und Prozessstabilität untersucht. Darüber hinaus wurde ein Modell entwickelt, um zwischen poren- vs. schichtdominierendem Polyelektrolytaufbau während der Modifikation zu unterscheiden. Ergebnisse identifizieren die PE- Schichtformation als einen weiteren entscheidenden Faktor während der Membranmodifikation. Bei Filtrationen im Labor- sowie Pilotmaßstab in Wasserwerken konnten hohe Rückhalteraten für zweiwertige Ionen (> 90 % für Sulfat und Magnesium und > 80 % für Calcium) erzielt werden. Jedoch wurden Prozessparameter identifiziert und weiterführend untersucht, die den resultierenden Ionenrückhalt beeinflussten. Eine hohe Ionenstärke im Feed führte zu einem Schwellen der PE-Struktur, was in einer Änderung der Trenneigenschaften resultierte. Dies war jedoch stark abhängig von der Art der vorhandenen Ionen und deren Konzentration. Modellgestützte Ergebnisse identifizierten Konzentrationspolarisation (CP) durch die laminare Grenzschicht als dominierenden Faktor für die Rückhalteeigenschaften der Membran. Neben der aus der Strömungsgeschwindigkeit resultierenden laminaren Grenzschichtdicke zeigten Ergebnisse zudem den starken Einfluss der Membranlänge auf die resultierende CP. Dies verdeutlicht eine Notwendigkeit zusätzlicher Experimente über den Labormaßstab hinaus. Weitere Untersuchungen im Labormaßstab zeigten, dass durch die Modifikation der Membranen ein MWCO im unteren Bereich von Nanofiltrationsmembranen erreicht werden konnte. Dies resultierte in hohen Entfernungsraten von gelösten natürlichen Substanzen (NOM). SAC254-Entfernung von > 90 % und TOC-Entfernung von > 80 % konnten sogar im Deadend-Betrieb erreicht werden. Dabei kam es zu höheren Rückhalten und niedrigeren Foulingraten bei einem höheren Anteil größerer Moleküle. Die Membranen blieben bis zu einem Rückspülflux von 50 L/(m² h) hinsichtlich ihres Trennverhaltens stabil. In Verbindung mit der guten chemischen Stabilität würde dies die Implementierung einer chemisch unterstützten Rückspülung ermöglichen, die eine hohe Effizienz bei der Entfernung von NOM-Fouling von der Membranoberfläche hatte. Insgesamt konnten Hohlfaser-UF-Membranen im Labormaßstab und in industriellem Maßstab erfolgreich mit der LbL-Technik modifiziert und mehrere Monate lang in zwei verschiedenen Wasserwerken betrieben werden. Die modifizierten Membranen kombinierten außergewöhnlich hohe NOM-Entfernungsraten mit der Möglichkeit eines hohen Rückhalts zweiwertiger Ionen und der Stabilität einer regelmäßigen mechanischen und chemischen Reinigung. Somit zeigen LbL-modifizierte Hohlfaser-UF-Membranen ein großes Potenzial für die Behandlung von Wässern mit hohem Gehalt an gelösten organischen Substanzen und Partikeln.Bundesministerium für Wirtschaft und Klimaschutz (BMWK)Deutscher Verein des Gas- und Wasserfaches e.V
From biomass to bioeconomy: engineering biocatalytic phosphorus mobilization from plant residues prior to animal feeding
No full textIn this work, the technical applicability of biocatalytic phosphorus (P)-mobilization from plant residues and the subsequent conversion of mobilized P into fertilizer has been investigated. Initially, P organically bound to phytate, is liberated by intrinsic and exogenous phytase enzymes. By conditioning plant residues prior to feeding, the enzymatic P-mobilization aims to generate high value feed material and promote a sustainable P-management. Rye bran, a by-product of the milling industry known for its high phytate content, is used as a model substrate in this research.
To monitor and evaluate the P-mobilization rate, an inline process analysis based on Fourier-Transform-Infrared spectroscopy was established. The developed inline analytical approach experienced a root mean squared error of prediction of 81 mgP∙100gbran-1, corresponding to a deviation of about 8% with respect to the total phytate content in rye bran. Using this approach, it is shown that metabolically induced germination activates intrinsic phytate hydrolyzing enzymes. Maximum intrinsic activity was identified at 43 °C, pH 5.3, and a bran to water ratio of 1 to 7 (w/v). Under these conditions, most of the phytate present was degraded within 30 min at a rate of 5565 U∙kgbran-1. For maximum P-mobilization, an exogenously applied phytase blend consisting of rPhyXT52 phytase and the phytase from D. castelli was used. Kinetic studies on the phytase blend demonstrated its suitability for batch operation. The P-mobilization process achieved complete elimination of phytate, resulting in a 90% reduction of the total P-content across different scales up to 400 L reactions. Supportive ultrasound as well as enzymatic treatment of the cellular matrix substantially increased the P-mobilization rate by over 90%. Among the enzyme formulations tested, xylanases showed the most pronounced effect. Struvite precipitation from the process wastewater containing the mobilized P achieved 99% P-recovery with over 90% purity at pH 9, 20 °C, and an equimolar input ratio of constitution ions. The results and observations indicate a very robust process and underline the feasibility and applicability of enzymatic P-mobilization and struvite precipitation for P-recovery on a larger scale. The production of value-added feed material through phytate depletion and utilization of phytate bound P in renewable resources contributes to a more resilient P-bioeconomy.In der vorliegenden Arbeit wurde die technische Umsetzbarkeit der biokatalytischen Phosphor-(P)-Mobilisierung aus pflanzlichen Reststoffen sowie die anschließende Umwandlung des freigesetzten P in Düngemittel umfassend untersucht. Ausgangspunkt ist die enzymatische Freisetzung von organisch an Phytat gebundenem Phosphor durch intrinsische sowie exogen zugeführte Phytasen. Ziel der Vorbehandlung von Pflanzenrückständen mittels enzymatischer P-Mobilisierung ist die Erzeugung hochwertiger Futtermittel sowie die Förderung eines nachhaltigen Phosphormanagements. Als Modellsubstrat diente Roggenkleie, ein Nebenprodukt der Müllereiindustrie mit hohem Phytatgehalt.
Zur Echtzeitüberwachung der P-Mobilisierung wurde eine Inline-Prozessanalytik auf Basis der Fourier-Transformations-Infrarotspektroskopie (FTIR) entwickelt und validiert. Der ermittelte Root Mean Squared Error of Prediction (RMSEP) lag bei 81 mgP∙100gKleie⁻¹, entsprechend einer Abweichung von ca. 8 % bezogen auf den Gesamtphytatgehalt der eingesetzten Roggenkleie. Die Ergebnisse belegen, dass metabolisch induzierte Keimungsprozesse zur Aktivierung intrinsischer phytathydrolysierender Enzyme führen. Die maximale intrinsische Enzymaktivität wurde bei 43 °C, einem pH-Wert von 5,3 und einem Feststoff-zu-Flüssig-Verhältnis von 1:7 (w/v) festgestellt. Unter diesen Bedingungen erfolgte der nahezu vollständige Phytatabbau innerhalb von 30 Minuten bei einer spezifischen Aktivität von 5565 U∙kgKleie⁻¹.
Zur Maximierung der P-Mobilisierung wurde eine exogene Phytaseformulierung, bestehend aus rPhyXT52-Phytase und der Phytase aus D. castelli, eingesetzt. Kinetische Untersuchungen belegten die Eignung dieser Phytasekombination für Batch-Prozesse. Im Rahmen der Prozessentwicklung konnte eine vollständige Phytatdegradation realisiert werden, was einer Reduktion des Gesamtphosphorgehalts um 90 % entsprach — sowohl im Labormaßstab als auch in Reaktoren mit einem Volumen von bis zu 400 Litern.
Zusätzliche Prozessintensivierung durch Ultraschallbehandlung sowie enzymatische Aufschlüsselung der Zellmatrix führte zu einer weiteren Steigerung der P-Mobilisierungsrate um über 90 %. Unter den getesteten enzymatischen Zusätzen zeigten insbesondere Xylanasen eine signifikante Effizienzsteigerung.
Die Rückgewinnung des mobilisierten Phosphors durch Struvitfällung aus dem Prozessabwasser erzielte eine P-Entfernungseffizienz von 99 % bei einer Produktreinheit von über 90 %, unter optimalen Bedingungen (pH 9, 20 °C, äquimolares Verhältnis der Konstitutionsionen). Die Gesamtbewertung des Verfahrens zeigt eine hohe Robustheit und bestätigt die technische Machbarkeit und Skalierbarkeit der enzymatischen P-Mobilisierung sowie der Struvitfällung zur Phosphorrückgewinnung.
Die Herstellung von höherwertigem Futtermaterial durch Phytatabbau und die effiziente Nutzung phytatge¬bundenen Phosphors aus nachwachsenden Rohstoffen tragen wesentlich zur Etablierung einer resilienteren P-Bioökonomie bei.Deutsche Bundesstiftung Umwel
Developing and testing 3D printed models of arteriovenous malformations for embolization training in interventional neuroradiology
No full textThe advancement of technology and the development of smaller treatment instruments has enabled the utilization of neurointerventional procedures to treat conditions affecting small vessels (>2mm). One example is an arteriovenous malformation (AVM), which can be treated by embolization. The embolization procedure is technically challenging and requires extensive training of the physicians. A number of training models have been developed which simulate the treatment of AVM in a flow model with original instruments, using the embolic agent Onyx. These AVM models are frequently intricate and time-consuming to fabricate. This paper presents the simple development of four AVM models for embolization simulations, which have been designed for integration into the existing neurointerventional training simulator, HANNES. The development and testing of the models were carried out by an interdisciplinary team of physicians and engineers. The application test was conducted in a real angiography suite with original treatment instruments and the embolic agent PHILTM by an experienced neurointerventional physician to evaluate the AVM models in regard to geometric mapping, haptics and embolization behaviour. The models offer a range of AVM embolization simulations within the HANNES environment, catering to diverse proficiency levels, from novice to advanced and expert users