490 Works

On the digital twin application and the role of artificial intelligence in additive manufacturing: a systematic review

Katharina Bartsch, Alexander Pettke, Artur Hübert, Julia Lakämper & Fritz Lange
Additive manufacturing (AM) as a highly digitalized manufacturing technology is capable of the implementation of the concept of the digital twin (DT), which promises highly automated and optimized part production. Since the DT is a quite novel concept requiring a wide framework of various technologies, it is not state of the art yet, though. Especially the combination with artificial intelligence (AI) methods is still challenging. Applying the methodology of the systematic review, the state of...

Predictability of vibration loads from experimental data by means of reduced vehicle models and machine learning

Leo Dostal, Helge Johannes Grossert, Daniel-André Dücker, Malte Grube, Daniel Kreuter, Kai Sandmann, Benjamin Zillmann & Robert Seifried
Nowadays electric cars are in the spotlight of automotive research. In this context we consider data based approaches as tools to improve and facilitate the car design process. Hereby, we address the challenge of vibration load prediction for electric cars using neural network based machine learning (ML), a data-based frequency response function approach, and a hybrid combined model. We extensively study the challenging case of vibration load prediction of car components, such as the traction...

Reliable GaN-based THz gunn diodes with side-contact and field-plate technologies

Ahid S. Hajo, Oktay Yilmazoglu, Armin Dadgar, Franko Küppers & Thomas Kusserow
For the first time, Gallium Nitride(GaN)-based Gunn diodes with side-contact and field-plate technologies were fabricated and measured with reliable characteristics. A high negative differential resistance (NDR) region was characterised for the GaN Gunn effect using side-contact technology. The I-V measurement of the THz diode showed the ohmic and the Gunn effect region with high forward current of 0.65A and high current drop of approximately 100mA for a small ring diode width w of 1.5 μm...

Process design of a multistage drying process via flowsheet simulation

Moritz Buchholz, Johannes Haus, Lukas Blesinger, Christian Riemann, Swantje Pietsch, Frank Kleine Jäger & Stefan Heinrich
Abstract Multistage drying processes including spray drying and fluidized bed unit operations are challenging to design due to the dependencies of the preceding process steps. Flowsheet simulation offers the possibility to simulate a complete process by the application of suitable short‐cut models. In this contribution a novel model for a spray dryer based on a population balance approach is presented. Furthermore, a dynamic model for a fluidized bed dryer is introduced. Experimental data is used...

On the potential of gassy marine soils triggering submarine slope instabilities

Pauline Kaminski & Jürgen Grabe
The development of debris flows and turbidity currents in the course of a submarine slope failure event can cause major damage in offshore infrastructure. Additionally, the tsunamogenic potential of large slope failures at continental margins poses a direct threat to coastal communities. Therefore, the trigger mechanisms of submarine slope failures have been thoroughly investigated in the past. However, the influence of free gas in the sediment, which has been observed close to several slide events,...

The grip concept of incisional hernia repair - dynamic bench test, CT abdomen with valsalva and 1-year clinical results

Friedrich Kallinowski, Dominik Gutjahr, Felix Harder, Mohammad Sabagh, Yannique Ludwig, Vladimir J. Lozanovski, Thorsten Löffler, Johannes Rinn, Johannes Görich, Annette Grimm, Matthias Vollmer & Regine Nessel
Incisional hernia is a frequent consequence of major surgery. Most repairs augment the abdominal wall with artificial meshes fixed to the tissues with sutures, tacks, or glue. Pain and recurrences plague at least 10–20% of the patients after repair of the abdominal defect. How should a repair of incisional hernias be constructed to achieve durability? Incisional hernia repair can be regarded as a compound technique. The biomechanical properties of a compound made of tissue, textile,...

Metal-doped carbons from polyurea-crosslinked alginate aerogel beads

Grigorios Raptopoulos, Maria Papastergiou, Despoina Chriti, Eleni Effraimopoulou, Tomaž Čendak, Nikolaos Samartzis, Gregor Mali, Theophilos Ioannides, Pavel Gurikov, Irina Smirnova & Patrina Paraskevopoulou
Metal-doped polyurea-crosslinked alginate aerogel beads (X-M-alginate; M: Ca, Co, Ni, Cu) were prepared via the reaction of an aromatic triisocyanate (Desmodur RE) with the -OH groups on the surface of pre-formed M-alginate wet gels, and with adsorbed gelation water. The X-M-alginate aerogels consisted of 49-63% polyurea and contained 2-7% metal ions; they were fibrous macro/meso/microporous materials with porosities up to 94% v/v, and BET surface areas 245-486 m2 g-1, comparable to those of native M-alginate...

Untersuchung eines LNG-Kompensators im kryogenen Bereich

Olivia Englert-Dudek
In der Schifffahrt werden durch den Antrieb mit Schweröl hohe klimaschädliche Emissionen verursacht. LNG gilt als Alternative zum Schweröl, da die Verbrennung von LNG eine deutliche Reduzierung der Emissionen mit sich bringt. Diese Arbeit beschäftigt sich mit der Einsatztauglichkeit eines LNG-Kompensators in Schiffen. Dazu wird in einem Versuch ein Kompensator in einer Klimakammer auf sein Verhalten hin untersucht. In diesem Versuch wird der Kompensator mit Flüssigstickstoff bis auf −160 C heruntergekühlt, um die Krafteinwirkung und...

A segmentation scheme for CLF dynamic movement control applied to robotic handwriting

Patrick Göttsch, Robin Olschewski & Herbert Werner
Control Lyapunov Function - Dynamic Movement is a recently proposed imitation learning approach for controlling point-to-point movements. In this work some practical issues arising with this approach have been investigated by studying a particular application: robotic handwriting of German letters. One difficulty in this context is the handling of crossings. Here a novel segmentation scheme is proposed to eliminate crossings. Using a segmentation framework for splitting up the movement into a number of partial movements...

Enzyme-enhanced CO2 absorption process in rotating packed bed

Justyna Wojtasik, Konrad Gładyszewski, Mirko Skiborowski, Andrzej Górak & Marcin Piątkowski
Carbon dioxide is considered the most important contributor to the global warming effect. To reduce greenhouse gas emissions, CO 2 should be separated from the exhaust gas stream in a selective way. The most often applied technology to capture CO 2 from exhaust gases is the reactive absorption in aqueous amine solutions, which is currently widely used in different industrial applications. The efficiency of this technology could be improved by applying high-gravity technologies that intensify...

Data-driven quasi-LPV model predictive control using koopman operator techniques

Pablo S. G. Cisneros, Adwait Datar, Patrick Göttsch & Herbert Werner
A fast data-driven extension of the velocity-based quasi-linear parameter-varying model predictive control (qLMPC) approach is proposed for scenarios where first principles models are not available or are computationally too expensive. We use tools from the recently proposed Koopman operator framework to identify a quasi-linear parameter-varying model (in input/output and state-space form) by choosing the observables from physical insight. An online update strategy to adapt to changes in the plant dynamics is also proposed. The approach...

Experimentelle Untersuchung des Stofftransports im mikroblasenbegasten Rührreaktor unter der Berücksichtigung von Gegendiffusionseffekten

Timo Alexander Merbach
Viele chemische und biologische Reaktionen in wässriger Phase benötigen gasförmige Komponenten, welche über Begasungseinrichtungen bereitgestellt werden. Für schnelle chemische und biologische Reaktionen ist der Stofftransport von der Gas- in die Flüssigphase häufig limitierend, was eine kontinuierliche Prozessoptimierung notwendig macht. Für diese Prozessoptimierung wird im Labor der Stofftransport über den volumenspezifischen Stoffdurchgangskoeffizienten kLa quantifiziert. Für die Bestimmung des kLa-Wertes wird in der Regel die Messmethode des Gasstrippings mit Stickstoff verwendet. Die vorliegende Arbeit konzentriert sich auf...

Circumference of essentially 4-connected planar triangulations

Igor Fabrici, Jochen Harant, Samuel Mohr & Jens M. Schmidt

Distributed control for complex mission scenarios with non-holonomic agents – an LPV approach

Aly Saeed Aly Aly Attallah
Diese Arbeit untersucht kooperative Regelstrategien für nicht-holonome, autonome Agenten, die als linear parametervariierende (LPV) Systeme modelliert werden. Es werden zwei verschiedene Ansätze untersucht. Zum einen die Formationsregelung; hierfür wird ein gekoppelter Information Flow Filter vorgestellt, der Feedback von lokalen Agenten in das Konsensprotokoll erlaubt. Weiterhin wird eine Methode für den simultanen Entwurf von Filter und lokalen Reglern entwickelt. Zum anderen wird eine Flocking-basierte Regelung betrachtet und für LPV-Agenten erweitert. Hier wird eine Separation im Entwurf...

Decoding rate-compatible 5G-LDPC codes with coarse quantization using the information bottleneck method

Maximilian Stark, Linfang Wang, Gerhard Bauch & Richard D. Wesel
Increased data rates and very low-latency requirements place strict constraints on thecomputational complexity of channel decoders in the new 5G communications standard. Practicallow-density parity-check (LDPC) decoder implementations use message-passing decoding with finiteprecision, which becomes coarse as complexity is more severely constrained. In turn, performance degradesas the precision becomes more coarse. Recently, the information bottleneck (IB) method was used to designmutual-information-maximizing mappings that replace conventional finite-precision node computations. Asa result, the exchanged messages in the IB...

Reconstruction of low-rank aggregation kernels in univariate population balance equations

Robin Ahrens & Sabine Le Borne
The dynamics of particle processes can be described by population balance equations which are governed by phenomena including growth, nucleation, breakage and aggregation. Estimating the kinetics of the aggregation phenomena from measured density data constitutes an ill-conditioned inverse problem. In this work, we focus on the aggregation problem and present an approach to estimate the aggregation kernel in discrete, low rank form from given (measured or simulated) data. The low-rank assumption for the kernel allows...

Smart chest X-ray worklist prioritization using artificial intelligence: a clinical workflow simulation

Ivo-Matteo Baltruschat, Leonhard A. Steinmeister, Hannes Nickisch, Axel Saalbach, Michael Grass, Gerhard Adam, Tobias Knopp & Harald Ittrich
Objective: The aim is to evaluate whether smart worklist prioritization by artificial intelligence (AI) can optimize the radiology workflow and reduce report turnaround times (RTATs) for critical findings in chest radiographs (CXRs). Furthermore, we investigate a method to counteract the effect of false negative predictions by AI—resulting in an extremely and dangerously long RTAT, as CXRs are sorted to the end of the worklist. Methods: We developed a simulation framework that models the current workflow...

Using natural language processing for supply chain mapping: a systematic review of current approaches

Henning Schöpper & Wolfgang Kersten
Purpose: The COVID-19 crisis has shown that the global supply chains are not as resilient as expected. First investigations indicate that the main contributing factor is a lack of visibility into the supply chain's lower tiers. Simultaneously, the willingness to share data in the supply chain is low as companies mainly consider their data as proprietary. However, large amounts of data are available on the internet. The amount of this data is steadily increasing; however,...

Synergistic and competitive adsorption of hydrophilic nanoparticles and oil-soluble surfactants at the oil-water interface

Joeri Smits, Rajendra P. Giri, Chen Shen, Diogo Mendonça, Bridget M. Murphy, Patrick Huber, Kurosch Rezwan & Michael Maas
Fundamental insights into the interplay and self-assembly of nanoparticles and surface-active agents at the liquid-liquid interface play a pivotal role in understanding the ubiquitous colloidal systems present in our natural surroundings, including foods and aquatic life, and in the industry for emulsion stabilization, drug delivery, or enhanced oil recovery. Moreover, well-controlled model systems for mixed interfacial adsorption of nanoparticles and surfactants allow unprecedented insights into nonideal or contaminated particle-stabilized emulsions. Here, we investigate such a...

Verteilung des Workloads und die Akzeptanz von formativem E-Assessment aus Studierendenperspektive

Nicole Podleschny, Katrin Billerbeck & Kai Gustav Mertens
Die Entwicklung von Flipped Classroom Konzepten mit E-Assessment Elementen ist eine Möglichkeit kontinuierliches Lernen zu fördern – aber mit einem hohen Aufwand für die Lehrenden verbunden. Bringt die Umstellung die gewünschten Effekte? Nutzen Studierende das Online-Modul tatsächlich auch zum kontinuierlichen Lernen - und nicht nur zum kurzfristigen Lernen direkt vor der Klausur?

All-suture anchor pullout results in decreased bone damage and depends on cortical thickness

Dimitris Ntalos, Gerd Huber, Kay Sellenschloh, Hiroaki Saito, Klaus Püschel, Michael Morlock, Karl-Heinz Frosch & Till Orla Klatte
Purpose: To evaluate the influence of cortical and cancellous bone structure on the biomechanical properties of all-suture and conventional anchors and compare the morphological bone damage after their failure. The hypothesis of the study is that all-suture anchor pullout is less invasive and that the pullout force is influenced by the cortical thickness. Methods: Thirty human humeri were biomechanically tested as follows: starting with a load cycle from 20 to 50 N, a stepwise increase...

3D-Laserscanner für BIM : eine vergleichende Kurzstudie

Johannes Hinckeldeyn & Marko Thiel

Soluble versions of outer membrane cytochromes function as exporters for heterologously produced cargo proteins

Helge M. Dietrich, Miriam Edel, Thea Viola Bursać, Manfred Meier, Katrin Sturm-Richter & Johannes Gescher
This study reveals that it is possible to secrete truncated versions of outer membrane cytochromes into the culture supernatant and that these proteins can provide a basis for the export of heterologously produced proteins. Different soluble and truncated versions of the outer membrane cytochrome MtrF were analyzed for their suitability to be secreted. A protein version with a very short truncation of the N-terminus to remove the recognition sequence for the addition of a lipid...

Efficient biochemical production of acetoin from carbon dioxide using Cupriavidus necator H16

Carina Windhorst & Johannes Gescher
Background: Cupriavidus necator is the best-studied knallgas (also termed hydrogen oxidizing) bacterium and provides a model organism for studying the production of the storage polymer polyhydroxybutyrate (PHB). Genetically engineered strains could be applied for the autotrophic production of valuable chemicals. Nevertheless, the efficiency of the catalyzed processes is generally believed to be lower than with acetogenic bacteria. Experimental data on the potential efficiency of autotrophic production with C. necator are sparse. Hence, this study aimed...

Addition of riboflavin-coupled magnetic beads increases current production in bioelectrochemical systems via the increased formation of anode-biofilms

Tutut Arinda, Laura-Alina Philipp, David Rehnlund, Miriam Edel, Jonas Chodorski, Markus Stöckl, Dirk Holtmann, Roland Ulber, Johannes Gescher & Katrin Sturm-Richter
Shewanella oneidensis is one of the best-understood model organisms for extracellular electron transfer. Endogenously produced and exported flavin molecules seem to play an important role in this process and mediate the connection between respiratory enzymes on the cell surface and the insoluble substrate by acting as electron shuttle and cytochrome-bound cofactor. Consequently, the addition of riboflavin to a bioelectrochemical system (BES) containing S. oneidensis cells as biocatalyst leads to a strong current increase. Still, an...

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  • 2021

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